diff --git a/.github/workflows/CICD.yml b/.github/workflows/CICD.yml
index bbbf60838..74f1d8ce0 100644
--- a/.github/workflows/CICD.yml
+++ b/.github/workflows/CICD.yml
@@ -638,7 +638,7 @@ jobs:
         # target-specific options
         # * CARGO_FEATURES_OPTION
         CARGO_FEATURES_OPTION='' ;
-        if [ -n "${{ matrix.job.features }}" ]; then CARGO_FEATURES_OPTION='--features "${{ matrix.job.features }}"' ; fi
+        if [ -n "${{ matrix.job.features }}" ]; then CARGO_FEATURES_OPTION='--features=${{ matrix.job.features }}' ; fi
         outputs CARGO_FEATURES_OPTION
         # * CARGO_USE_CROSS (truthy)
         CARGO_USE_CROSS='true' ; case '${{ matrix.job.use-cross }}' in ''|0|f|false|n|no) unset CARGO_USE_CROSS ;; esac;
@@ -705,7 +705,7 @@ jobs:
         ## Dependent VARs setup
         outputs() { step_id="dep_vars"; for var in "$@" ; do echo steps.${step_id}.outputs.${var}="${!var}"; echo ::set-output name=${var}::${!var}; done; }
         # * determine sub-crate utility list
-        UTILITY_LIST="$(./util/show-utils.sh ${CARGO_FEATURES_OPTION})"
+        UTILITY_LIST="$(./util/show-utils.sh ${{ steps.vars.outputs.CARGO_FEATURES_OPTION }})"
         echo UTILITY_LIST=${UTILITY_LIST}
         CARGO_UTILITY_LIST_OPTIONS="$(for u in ${UTILITY_LIST}; do echo "-puu_${u}"; done;)"
         outputs CARGO_UTILITY_LIST_OPTIONS
@@ -948,7 +948,7 @@ jobs:
         # target-specific options
         # * CARGO_FEATURES_OPTION
         CARGO_FEATURES_OPTION='--all-features' ;  ## default to '--all-features' for code coverage
-        if [ -n "${{ matrix.job.features }}" ]; then CARGO_FEATURES_OPTION='--features "${{ matrix.job.features }}"' ; fi
+        if [ -n "${{ matrix.job.features }}" ]; then CARGO_FEATURES_OPTION='--features=${{ matrix.job.features }}' ; fi
         outputs CARGO_FEATURES_OPTION
         # * CODECOV_FLAGS
         CODECOV_FLAGS=$( echo "${{ matrix.job.os }}" | sed 's/[^[:alnum:]]/_/g' )
@@ -988,7 +988,7 @@ jobs:
         ## Dependent VARs setup
         outputs() { step_id="dep_vars"; for var in "$@" ; do echo steps.${step_id}.outputs.${var}="${!var}"; echo ::set-output name=${var}::${!var}; done; }
         # * determine sub-crate utility list
-        UTILITY_LIST="$(./util/show-utils.sh ${CARGO_FEATURES_OPTION})"
+        UTILITY_LIST="$(./util/show-utils.sh ${{ steps.vars.outputs.CARGO_FEATURES_OPTION }})"
         CARGO_UTILITY_LIST_OPTIONS="$(for u in ${UTILITY_LIST}; do echo "-puu_${u}"; done;)"
         outputs CARGO_UTILITY_LIST_OPTIONS
     - name: Test uucore
diff --git a/.vscode/cspell.dictionaries/acronyms+names.wordlist.txt b/.vscode/cspell.dictionaries/acronyms+names.wordlist.txt
index 53307bf35..81bc3bc5f 100644
--- a/.vscode/cspell.dictionaries/acronyms+names.wordlist.txt
+++ b/.vscode/cspell.dictionaries/acronyms+names.wordlist.txt
@@ -48,6 +48,7 @@ EditorConfig
 FreeBSD
 Gmail
 GNU
+Illumos
 Irix
 MS-DOS
 MSDOS
diff --git a/Cargo.lock b/Cargo.lock
index 70f117b84..8e159029a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -280,9 +280,9 @@ dependencies = [
 
 [[package]]
 name = "clap"
-version = "3.0.10"
+version = "3.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7a30c3bf9ff12dfe5dae53f0a96e0febcd18420d1c0e7fad77796d9d5c4b5375"
+checksum = "d8c93436c21e4698bacadf42917db28b23017027a4deccb35dbe47a7e7840123"
 dependencies = [
  "atty",
  "bitflags",
@@ -292,7 +292,7 @@ dependencies = [
  "strsim 0.10.0",
  "termcolor",
  "terminal_size",
- "textwrap 0.14.2",
+ "textwrap 0.15.0",
 ]
 
 [[package]]
@@ -301,7 +301,7 @@ version = "3.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d044e9db8cd0f68191becdeb5246b7462e4cf0c069b19ae00d1bf3fa9889498d"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
 ]
 
 [[package]]
@@ -331,7 +331,7 @@ version = "0.0.12"
 dependencies = [
  "atty",
  "chrono",
- "clap 3.0.10",
+ "clap 3.1.6",
  "clap_complete",
  "conv",
  "filetime",
@@ -349,7 +349,7 @@ dependencies = [
  "selinux",
  "sha1",
  "tempfile",
- "textwrap 0.14.2",
+ "textwrap 0.15.0",
  "time",
  "unindent",
  "unix_socket",
@@ -1065,9 +1065,9 @@ checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55"
 
 [[package]]
 name = "libc"
-version = "0.2.113"
+version = "0.2.121"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eef78b64d87775463c549fbd80e19249ef436ea3bf1de2a1eb7e717ec7fab1e9"
+checksum = "efaa7b300f3b5fe8eb6bf21ce3895e1751d9665086af2d64b42f19701015ff4f"
 
 [[package]]
 name = "libloading"
@@ -1375,9 +1375,9 @@ dependencies = [
 
 [[package]]
 name = "ouroboros"
-version = "0.14.2"
+version = "0.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "71643f290d126e18ac2598876d01e1d57aed164afc78fdb6e2a0c6589a1f6662"
+checksum = "9f31a3b678685b150cba82b702dcdc5e155893f63610cf388d30cd988d4ca2bf"
 dependencies = [
  "aliasable",
  "ouroboros_macro",
@@ -1386,9 +1386,9 @@ dependencies = [
 
 [[package]]
 name = "ouroboros_macro"
-version = "0.14.2"
+version = "0.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed9a247206016d424fe8497bc611e510887af5c261fbbf977877c4bb55ca4d82"
+checksum = "084fd65d5dd8b3772edccb5ffd1e4b7eba43897ecd0f9401e330e8c542959408"
 dependencies = [
  "Inflector",
  "proc-macro-error",
@@ -2087,9 +2087,9 @@ dependencies = [
 
 [[package]]
 name = "textwrap"
-version = "0.14.2"
+version = "0.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0066c8d12af8b5acd21e00547c3797fde4e8677254a7ee429176ccebbe93dd80"
+checksum = "b1141d4d61095b28419e22cb0bbf02755f5e54e0526f97f1e3d1d160e60885fb"
 dependencies = [
  "smawk",
  "terminal_size",
@@ -2282,7 +2282,7 @@ checksum = "7cf7d77f457ef8dfa11e4cd5933c5ddb5dc52a94664071951219a97710f0a32b"
 name = "uu_arch"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "platform-info",
  "uucore",
 ]
@@ -2291,7 +2291,7 @@ dependencies = [
 name = "uu_base32"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2307,7 +2307,7 @@ dependencies = [
 name = "uu_basename"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2315,7 +2315,7 @@ dependencies = [
 name = "uu_basenc"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uu_base32",
  "uucore",
 ]
@@ -2325,7 +2325,7 @@ name = "uu_cat"
 version = "0.0.12"
 dependencies = [
  "atty",
- "clap 3.0.10",
+ "clap 3.1.6",
  "nix 0.23.1",
  "thiserror",
  "unix_socket",
@@ -2336,7 +2336,7 @@ dependencies = [
 name = "uu_chcon"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "fts-sys",
  "libc",
  "selinux",
@@ -2348,7 +2348,7 @@ dependencies = [
 name = "uu_chgrp"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2356,7 +2356,7 @@ dependencies = [
 name = "uu_chmod"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2365,7 +2365,7 @@ dependencies = [
 name = "uu_chown"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2373,7 +2373,7 @@ dependencies = [
 name = "uu_chroot"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2381,7 +2381,7 @@ dependencies = [
 name = "uu_cksum"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2389,7 +2389,7 @@ dependencies = [
 name = "uu_comm"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2397,7 +2397,7 @@ dependencies = [
 name = "uu_cp"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "exacl",
  "filetime",
  "ioctl-sys",
@@ -2414,7 +2414,7 @@ dependencies = [
 name = "uu_csplit"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "regex",
  "thiserror",
  "uucore",
@@ -2426,7 +2426,7 @@ version = "0.0.12"
 dependencies = [
  "atty",
  "bstr",
- "clap 3.0.10",
+ "clap 3.1.6",
  "memchr 2.4.1",
  "uucore",
 ]
@@ -2436,7 +2436,7 @@ name = "uu_date"
 version = "0.0.12"
 dependencies = [
  "chrono",
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
  "winapi 0.3.9",
@@ -2447,7 +2447,7 @@ name = "uu_dd"
 version = "0.0.12"
 dependencies = [
  "byte-unit",
- "clap 3.0.10",
+ "clap 3.1.6",
  "gcd",
  "libc",
  "signal-hook",
@@ -2458,7 +2458,7 @@ dependencies = [
 name = "uu_df"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "number_prefix",
  "uucore",
 ]
@@ -2467,7 +2467,7 @@ dependencies = [
 name = "uu_dircolors"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "glob",
  "uucore",
 ]
@@ -2476,7 +2476,7 @@ dependencies = [
 name = "uu_dirname"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2485,7 +2485,7 @@ name = "uu_du"
 version = "0.0.12"
 dependencies = [
  "chrono",
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
  "winapi 0.3.9",
 ]
@@ -2494,7 +2494,7 @@ dependencies = [
 name = "uu_echo"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2502,7 +2502,7 @@ dependencies = [
 name = "uu_env"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "rust-ini",
  "uucore",
 ]
@@ -2511,7 +2511,7 @@ dependencies = [
 name = "uu_expand"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "unicode-width",
  "uucore",
 ]
@@ -2520,7 +2520,7 @@ dependencies = [
 name = "uu_expr"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "num-bigint",
  "num-traits",
  "onig",
@@ -2531,7 +2531,7 @@ dependencies = [
 name = "uu_factor"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "coz",
  "num-traits",
  "paste",
@@ -2545,7 +2545,7 @@ dependencies = [
 name = "uu_false"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2553,7 +2553,7 @@ dependencies = [
 name = "uu_fmt"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "unicode-width",
  "uucore",
 ]
@@ -2562,7 +2562,7 @@ dependencies = [
 name = "uu_fold"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2570,7 +2570,7 @@ dependencies = [
 name = "uu_groups"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2580,7 +2580,7 @@ version = "0.0.12"
 dependencies = [
  "blake2b_simd",
  "blake3",
- "clap 3.0.10",
+ "clap 3.1.6",
  "digest",
  "hex",
  "md-5",
@@ -2596,7 +2596,7 @@ dependencies = [
 name = "uu_head"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "memchr 2.4.1",
  "uucore",
 ]
@@ -2605,7 +2605,7 @@ dependencies = [
 name = "uu_hostid"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2614,7 +2614,7 @@ dependencies = [
 name = "uu_hostname"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "hostname",
  "uucore",
  "winapi 0.3.9",
@@ -2624,7 +2624,7 @@ dependencies = [
 name = "uu_id"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "selinux",
  "uucore",
 ]
@@ -2633,7 +2633,7 @@ dependencies = [
 name = "uu_install"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "file_diff",
  "filetime",
  "libc",
@@ -2644,7 +2644,7 @@ dependencies = [
 name = "uu_join"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "memchr 2.4.1",
  "uucore",
 ]
@@ -2653,7 +2653,7 @@ dependencies = [
 name = "uu_kill"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2662,7 +2662,7 @@ dependencies = [
 name = "uu_link"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2670,7 +2670,7 @@ dependencies = [
 name = "uu_ln"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2678,7 +2678,7 @@ dependencies = [
 name = "uu_logname"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2689,7 +2689,7 @@ version = "0.0.12"
 dependencies = [
  "atty",
  "chrono",
- "clap 3.0.10",
+ "clap 3.1.6",
  "glob",
  "lazy_static",
  "lscolors",
@@ -2706,7 +2706,7 @@ dependencies = [
 name = "uu_mkdir"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2714,7 +2714,7 @@ dependencies = [
 name = "uu_mkfifo"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2723,7 +2723,7 @@ dependencies = [
 name = "uu_mknod"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2732,7 +2732,7 @@ dependencies = [
 name = "uu_mktemp"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "rand",
  "tempfile",
  "uucore",
@@ -2743,7 +2743,7 @@ name = "uu_more"
 version = "0.0.12"
 dependencies = [
  "atty",
- "clap 3.0.10",
+ "clap 3.1.6",
  "crossterm",
  "nix 0.23.1",
  "unicode-segmentation",
@@ -2755,7 +2755,7 @@ dependencies = [
 name = "uu_mv"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "fs_extra",
  "uucore",
 ]
@@ -2764,7 +2764,7 @@ dependencies = [
 name = "uu_nice"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "nix 0.23.1",
  "uucore",
@@ -2774,7 +2774,7 @@ dependencies = [
 name = "uu_nl"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "regex",
  "uucore",
 ]
@@ -2784,7 +2784,7 @@ name = "uu_nohup"
 version = "0.0.12"
 dependencies = [
  "atty",
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2793,7 +2793,7 @@ dependencies = [
 name = "uu_nproc"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "num_cpus",
  "uucore",
@@ -2803,7 +2803,7 @@ dependencies = [
 name = "uu_numfmt"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2812,7 +2812,7 @@ name = "uu_od"
 version = "0.0.12"
 dependencies = [
  "byteorder",
- "clap 3.0.10",
+ "clap 3.1.6",
  "half",
  "uucore",
 ]
@@ -2821,7 +2821,7 @@ dependencies = [
 name = "uu_paste"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2829,7 +2829,7 @@ dependencies = [
 name = "uu_pathchk"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2838,7 +2838,7 @@ dependencies = [
 name = "uu_pinky"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2847,7 +2847,7 @@ name = "uu_pr"
 version = "0.0.12"
 dependencies = [
  "chrono",
- "clap 3.0.10",
+ "clap 3.1.6",
  "itertools",
  "quick-error",
  "regex",
@@ -2858,7 +2858,7 @@ dependencies = [
 name = "uu_printenv"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2866,7 +2866,7 @@ dependencies = [
 name = "uu_printf"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2874,7 +2874,7 @@ dependencies = [
 name = "uu_ptx"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "regex",
  "uucore",
 ]
@@ -2883,7 +2883,7 @@ dependencies = [
 name = "uu_pwd"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2891,7 +2891,7 @@ dependencies = [
 name = "uu_readlink"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2899,7 +2899,7 @@ dependencies = [
 name = "uu_realpath"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2907,7 +2907,7 @@ dependencies = [
 name = "uu_relpath"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2915,7 +2915,7 @@ dependencies = [
 name = "uu_rm"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "remove_dir_all",
  "uucore",
  "walkdir",
@@ -2926,7 +2926,7 @@ dependencies = [
 name = "uu_rmdir"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -2935,7 +2935,7 @@ dependencies = [
 name = "uu_runcon"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "selinux",
  "thiserror",
@@ -2947,7 +2947,7 @@ name = "uu_seq"
 version = "0.0.12"
 dependencies = [
  "bigdecimal",
- "clap 3.0.10",
+ "clap 3.1.6",
  "num-bigint",
  "num-traits",
  "uucore",
@@ -2957,7 +2957,7 @@ dependencies = [
 name = "uu_shred"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "rand",
  "uucore",
 ]
@@ -2966,7 +2966,7 @@ dependencies = [
 name = "uu_shuf"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "rand",
  "rand_core",
  "uucore",
@@ -2976,7 +2976,7 @@ dependencies = [
 name = "uu_sleep"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -2985,7 +2985,7 @@ name = "uu_sort"
 version = "0.0.12"
 dependencies = [
  "binary-heap-plus",
- "clap 3.0.10",
+ "clap 3.1.6",
  "compare",
  "ctrlc",
  "fnv",
@@ -3003,7 +3003,7 @@ dependencies = [
 name = "uu_split"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "memchr 2.4.1",
  "uucore",
 ]
@@ -3012,7 +3012,7 @@ dependencies = [
 name = "uu_stat"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3020,7 +3020,7 @@ dependencies = [
 name = "uu_stdbuf"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "tempfile",
  "uu_stdbuf_libstdbuf",
  "uucore",
@@ -3040,7 +3040,7 @@ dependencies = [
 name = "uu_sum"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3048,7 +3048,7 @@ dependencies = [
 name = "uu_sync"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
  "winapi 0.3.9",
@@ -3058,7 +3058,7 @@ dependencies = [
 name = "uu_tac"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "memchr 2.4.1",
  "memmap2",
  "regex",
@@ -3069,7 +3069,7 @@ dependencies = [
 name = "uu_tail"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "nix 0.23.1",
  "uucore",
@@ -3080,7 +3080,7 @@ dependencies = [
 name = "uu_tee"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "retain_mut",
  "uucore",
@@ -3090,7 +3090,7 @@ dependencies = [
 name = "uu_test"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "redox_syscall",
  "uucore",
@@ -3100,7 +3100,7 @@ dependencies = [
 name = "uu_timeout"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "nix 0.23.1",
  "uucore",
@@ -3110,7 +3110,7 @@ dependencies = [
 name = "uu_touch"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "filetime",
  "time",
  "uucore",
@@ -3121,7 +3121,7 @@ dependencies = [
 name = "uu_tr"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "nom",
  "uucore",
 ]
@@ -3130,7 +3130,7 @@ dependencies = [
 name = "uu_true"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3138,7 +3138,7 @@ dependencies = [
 name = "uu_truncate"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3146,7 +3146,7 @@ dependencies = [
 name = "uu_tsort"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3155,7 +3155,7 @@ name = "uu_tty"
 version = "0.0.12"
 dependencies = [
  "atty",
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
 ]
@@ -3164,7 +3164,7 @@ dependencies = [
 name = "uu_uname"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "platform-info",
  "uucore",
 ]
@@ -3173,7 +3173,7 @@ dependencies = [
 name = "uu_unexpand"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "unicode-width",
  "uucore",
 ]
@@ -3182,7 +3182,7 @@ dependencies = [
 name = "uu_uniq"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "strum",
  "strum_macros",
  "uucore",
@@ -3192,7 +3192,7 @@ dependencies = [
 name = "uu_unlink"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3201,7 +3201,7 @@ name = "uu_uptime"
 version = "0.0.12"
 dependencies = [
  "chrono",
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3209,7 +3209,7 @@ dependencies = [
 name = "uu_users"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3218,7 +3218,7 @@ name = "uu_wc"
 version = "0.0.12"
 dependencies = [
  "bytecount",
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "nix 0.23.1",
  "unicode-width",
@@ -3230,7 +3230,7 @@ dependencies = [
 name = "uu_who"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "uucore",
 ]
 
@@ -3238,7 +3238,7 @@ dependencies = [
 name = "uu_whoami"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "libc",
  "uucore",
  "winapi 0.3.9",
@@ -3248,7 +3248,7 @@ dependencies = [
 name = "uu_yes"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "nix 0.23.1",
  "uucore",
 ]
@@ -3257,7 +3257,7 @@ dependencies = [
 name = "uucore"
 version = "0.0.12"
 dependencies = [
- "clap 3.0.10",
+ "clap 3.1.6",
  "data-encoding",
  "data-encoding-macro",
  "dns-lookup",
diff --git a/Cargo.toml b/Cargo.toml
index 43797e71e..517752e32 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -245,11 +245,11 @@ test = [ "uu_test" ]
 [workspace]
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 clap_complete = "3.0"
 phf = "0.10.1"
 lazy_static = { version="1.3" }
-textwrap = { version="0.14", features=["terminal_size"] }
+textwrap = { version="0.15", features=["terminal_size"] }
 uucore = { version=">=0.0.11", package="uucore", path="src/uucore" }
 selinux = { version="0.2", optional = true }
 ureq = "2.4.0"
diff --git a/build.rs b/build.rs
index c4f135e64..50b8cfa3f 100644
--- a/build.rs
+++ b/build.rs
@@ -43,7 +43,7 @@ pub fn main() {
     let mut tf = File::create(Path::new(&out_dir).join("test_modules.rs")).unwrap();
 
     mf.write_all(
-        "type UtilityMap<T> = phf::Map<&'static str, (fn(T) -> i32, fn() -> App<'static>)>;\n\
+        "type UtilityMap<T> = phf::Map<&'static str, (fn(T) -> i32, fn() -> Command<'static>)>;\n\
          \n\
          fn util_map<T: uucore::Args>() -> UtilityMap<T> {\n"
             .as_bytes(),
diff --git a/docs/compiles_table.py b/docs/compiles_table.py
index aa1b8703c..e2c4c0a8d 100644
--- a/docs/compiles_table.py
+++ b/docs/compiles_table.py
@@ -40,6 +40,8 @@ TARGETS = [
     "x86_64-linux-android",
     # Solaris
     "x86_64-sun-solaris",
+    # Illumos
+    "x86_64-unknown-illumos",
     # WASM
     "wasm32-wasi",
     # Redox
diff --git a/src/bin/coreutils.rs b/src/bin/coreutils.rs
index fcd86c93f..7a8986035 100644
--- a/src/bin/coreutils.rs
+++ b/src/bin/coreutils.rs
@@ -5,7 +5,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-use clap::{App, Arg};
+use clap::{Arg, Command};
 use clap_complete::Shell;
 use std::cmp;
 use std::ffi::OsStr;
@@ -138,7 +138,7 @@ fn gen_completions<T: uucore::Args>(
         .chain(util_map.keys().copied())
         .collect();
 
-    let matches = App::new("completion")
+    let matches = Command::new("completion")
         .about("Prints completions to stdout")
         .arg(
             Arg::new("utility")
@@ -155,7 +155,7 @@ fn gen_completions<T: uucore::Args>(
     let utility = matches.value_of("utility").unwrap();
     let shell = matches.value_of("shell").unwrap();
 
-    let mut app = if utility == "coreutils" {
+    let mut command = if utility == "coreutils" {
         gen_coreutils_app(util_map)
     } else {
         util_map.get(utility).unwrap().1()
@@ -163,15 +163,15 @@ fn gen_completions<T: uucore::Args>(
     let shell: Shell = shell.parse().unwrap();
     let bin_name = std::env::var("PROG_PREFIX").unwrap_or_default() + utility;
 
-    clap_complete::generate(shell, &mut app, bin_name, &mut io::stdout());
+    clap_complete::generate(shell, &mut command, bin_name, &mut io::stdout());
     io::stdout().flush().unwrap();
     process::exit(0);
 }
 
-fn gen_coreutils_app<T: uucore::Args>(util_map: &UtilityMap<T>) -> App<'static> {
-    let mut app = App::new("coreutils");
+fn gen_coreutils_app<T: uucore::Args>(util_map: &UtilityMap<T>) -> Command<'static> {
+    let mut command = Command::new("coreutils");
     for (_, (_, sub_app)) in util_map {
-        app = app.subcommand(sub_app());
+        command = command.subcommand(sub_app());
     }
-    app
+    command
 }
diff --git a/src/bin/uudoc.rs b/src/bin/uudoc.rs
index a6bc16cc2..24c347fe7 100644
--- a/src/bin/uudoc.rs
+++ b/src/bin/uudoc.rs
@@ -4,7 +4,7 @@
 // file that was distributed with this source code.
 // spell-checker:ignore tldr
 
-use clap::App;
+use clap::Command;
 use std::ffi::OsString;
 use std::fs::File;
 use std::io::Cursor;
@@ -46,13 +46,13 @@ fn main() -> io::Result<()> {
 
     let mut utils = utils.entries().collect::<Vec<_>>();
     utils.sort();
-    for (&name, (_, app)) in utils {
+    for (&name, (_, command)) in utils {
         if name == "[" {
             continue;
         }
         let p = format!("docs/src/utils/{}.md", name);
         if let Ok(f) = File::create(&p) {
-            write_markdown(f, &mut app(), name, &mut tldr_zip)?;
+            write_markdown(f, &mut command(), name, &mut tldr_zip)?;
             println!("Wrote to '{}'", p);
         } else {
             println!("Error writing to {}", p);
@@ -64,29 +64,29 @@ fn main() -> io::Result<()> {
 
 fn write_markdown(
     mut w: impl Write,
-    app: &mut App,
+    command: &mut Command,
     name: &str,
     tldr_zip: &mut zip::ZipArchive<impl Read + Seek>,
 ) -> io::Result<()> {
     write!(w, "# {}\n\n", name)?;
-    write_version(&mut w, app)?;
-    write_usage(&mut w, app, name)?;
-    write_description(&mut w, app)?;
-    write_options(&mut w, app)?;
+    write_version(&mut w, command)?;
+    write_usage(&mut w, command, name)?;
+    write_description(&mut w, command)?;
+    write_options(&mut w, command)?;
     write_examples(&mut w, name, tldr_zip)
 }
 
-fn write_version(w: &mut impl Write, app: &App) -> io::Result<()> {
+fn write_version(w: &mut impl Write, command: &Command) -> io::Result<()> {
     writeln!(
         w,
         "<div class=\"version\">version: {}</div>",
-        app.render_version().split_once(' ').unwrap().1
+        command.render_version().split_once(' ').unwrap().1
     )
 }
 
-fn write_usage(w: &mut impl Write, app: &mut App, name: &str) -> io::Result<()> {
+fn write_usage(w: &mut impl Write, command: &mut Command, name: &str) -> io::Result<()> {
     writeln!(w, "\n```")?;
-    let mut usage: String = app
+    let mut usage: String = command
         .render_usage()
         .lines()
         .skip(1)
@@ -99,8 +99,8 @@ fn write_usage(w: &mut impl Write, app: &mut App, name: &str) -> io::Result<()>
     writeln!(w, "```")
 }
 
-fn write_description(w: &mut impl Write, app: &App) -> io::Result<()> {
-    if let Some(about) = app.get_long_about().or_else(|| app.get_about()) {
+fn write_description(w: &mut impl Write, command: &Command) -> io::Result<()> {
+    if let Some(about) = command.get_long_about().or_else(|| command.get_about()) {
         writeln!(w, "{}", about)
     } else {
         Ok(())
@@ -152,10 +152,10 @@ fn get_zip_content(archive: &mut ZipArchive<impl Read + Seek>, name: &str) -> Op
     Some(s)
 }
 
-fn write_options(w: &mut impl Write, app: &App) -> io::Result<()> {
+fn write_options(w: &mut impl Write, command: &Command) -> io::Result<()> {
     writeln!(w, "<h2>Options</h2>")?;
     write!(w, "<dl>")?;
-    for arg in app.get_arguments() {
+    for arg in command.get_arguments() {
         write!(w, "<dt>")?;
         let mut first = true;
         for l in arg.get_long_and_visible_aliases().unwrap_or_default() {
diff --git a/src/uu/arch/Cargo.toml b/src/uu/arch/Cargo.toml
index 207100f59..96f6c4c8a 100644
--- a/src/uu/arch/Cargo.toml
+++ b/src/uu/arch/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/arch.rs"
 
 [dependencies]
 platform-info = "0.2"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/arch/src/arch.rs b/src/uu/arch/src/arch.rs
index b588adbb9..502e2d5a0 100644
--- a/src/uu/arch/src/arch.rs
+++ b/src/uu/arch/src/arch.rs
@@ -8,7 +8,7 @@
 
 use platform_info::*;
 
-use clap::{crate_version, App, AppSettings};
+use clap::{crate_version, Command};
 use uucore::error::{FromIo, UResult};
 
 static ABOUT: &str = "Display machine architecture";
@@ -23,10 +23,10 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
 }
diff --git a/src/uu/base32/Cargo.toml b/src/uu/base32/Cargo.toml
index 0b695f0aa..d61477fee 100644
--- a/src/uu/base32/Cargo.toml
+++ b/src/uu/base32/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/base32.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features = ["encoding"] }
 
 [[bin]]
diff --git a/src/uu/base32/src/base32.rs b/src/uu/base32/src/base32.rs
index ff1ba502a..4260c472e 100644
--- a/src/uu/base32/src/base32.rs
+++ b/src/uu/base32/src/base32.rs
@@ -7,7 +7,7 @@
 
 use std::io::{stdin, Read};
 
-use clap::App;
+use clap::Command;
 use uucore::{encoding::Format, error::UResult};
 
 pub mod base_common;
@@ -44,6 +44,6 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     )
 }
 
-pub fn uu_app<'a>() -> App<'a> {
+pub fn uu_app<'a>() -> Command<'a> {
     base_common::base_app(ABOUT, USAGE)
 }
diff --git a/src/uu/base32/src/base_common.rs b/src/uu/base32/src/base_common.rs
index 1d4d8a19d..100c85b1f 100644
--- a/src/uu/base32/src/base_common.rs
+++ b/src/uu/base32/src/base_common.rs
@@ -18,7 +18,7 @@ use std::fs::File;
 use std::io::{BufReader, Stdin};
 use std::path::Path;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 
 pub static BASE_CMD_PARSE_ERROR: i32 = 1;
 
@@ -86,19 +86,19 @@ impl Config {
 }
 
 pub fn parse_base_cmd_args(args: impl uucore::Args, about: &str, usage: &str) -> UResult<Config> {
-    let app = base_app(about, usage);
+    let command = base_app(about, usage);
     let arg_list = args
         .collect_str(InvalidEncodingHandling::ConvertLossy)
         .accept_any();
-    Config::from(&app.get_matches_from(arg_list))
+    Config::from(&command.get_matches_from(arg_list))
 }
 
-pub fn base_app<'a>(about: &'a str, usage: &'a str) -> App<'a> {
-    App::new(uucore::util_name())
+pub fn base_app<'a>(about: &'a str, usage: &'a str) -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(about)
         .override_usage(format_usage(usage))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         // Format arguments.
         .arg(
             Arg::new(options::DECODE)
diff --git a/src/uu/basename/Cargo.toml b/src/uu/basename/Cargo.toml
index 6426e5046..399433109 100644
--- a/src/uu/basename/Cargo.toml
+++ b/src/uu/basename/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/basename.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/basename/src/basename.rs b/src/uu/basename/src/basename.rs
index bf13fde7e..7b0a0a486 100644
--- a/src/uu/basename/src/basename.rs
+++ b/src/uu/basename/src/basename.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) fullname
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::path::{is_separator, PathBuf};
 use uucore::display::Quotable;
 use uucore::error::{UResult, UUsageError};
@@ -87,12 +87,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(SUMMARY)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::MULTIPLE)
                 .short('a')
diff --git a/src/uu/basenc/Cargo.toml b/src/uu/basenc/Cargo.toml
index a0f652cee..638c7e26c 100644
--- a/src/uu/basenc/Cargo.toml
+++ b/src/uu/basenc/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/basenc.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features = ["encoding"] }
 uu_base32 = { version=">=0.0.8", package="uu_base32", path="../base32"}
 
diff --git a/src/uu/basenc/src/basenc.rs b/src/uu/basenc/src/basenc.rs
index 9e48cf80c..d47fe123a 100644
--- a/src/uu/basenc/src/basenc.rs
+++ b/src/uu/basenc/src/basenc.rs
@@ -8,7 +8,7 @@
 
 //spell-checker:ignore (args) lsbf msbf
 
-use clap::{App, Arg};
+use clap::{Arg, Command};
 use uu_base32::base_common::{self, Config, BASE_CMD_PARSE_ERROR};
 
 use uucore::{
@@ -40,12 +40,12 @@ const ENCODINGS: &[(&str, Format)] = &[
 
 const USAGE: &str = "{} [OPTION]... [FILE]";
 
-pub fn uu_app<'a>() -> App<'a> {
-    let mut app = base_common::base_app(ABOUT, USAGE);
+pub fn uu_app<'a>() -> Command<'a> {
+    let mut command = base_common::base_app(ABOUT, USAGE);
     for encoding in ENCODINGS {
-        app = app.arg(Arg::new(encoding.0).long(encoding.0));
+        command = command.arg(Arg::new(encoding.0).long(encoding.0));
     }
-    app
+    command
 }
 
 fn parse_cmd_args(args: impl uucore::Args) -> UResult<(Config, Format)> {
diff --git a/src/uu/cat/Cargo.toml b/src/uu/cat/Cargo.toml
index 760ff3f3a..a0466226f 100644
--- a/src/uu/cat/Cargo.toml
+++ b/src/uu/cat/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/cat.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 thiserror = "1.0"
 atty = "0.2"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs", "pipes"] }
diff --git a/src/uu/cat/src/cat.rs b/src/uu/cat/src/cat.rs
index 0a1ba2559..edba1b8d0 100644
--- a/src/uu/cat/src/cat.rs
+++ b/src/uu/cat/src/cat.rs
@@ -14,7 +14,7 @@
 extern crate unix_socket;
 
 // last synced with: cat (GNU coreutils) 8.13
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::{metadata, File};
 use std::io::{self, Read, Write};
 use thiserror::Error;
@@ -239,13 +239,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     cat_files(&files, &options)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FILE)
                 .hide(true)
diff --git a/src/uu/chcon/Cargo.toml b/src/uu/chcon/Cargo.toml
index 75ce3fbd9..4a001b885 100644
--- a/src/uu/chcon/Cargo.toml
+++ b/src/uu/chcon/Cargo.toml
@@ -14,7 +14,7 @@ edition = "2018"
 path = "src/chcon.rs"
 
 [dependencies]
-clap         = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap         = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore       = { version = ">=0.0.9", package="uucore", path="../../uucore", features=["entries", "fs", "perms"] }
 selinux      = { version = "0.2"   }
 fts-sys      = { version = "0.2"   }
diff --git a/src/uu/chcon/src/chcon.rs b/src/uu/chcon/src/chcon.rs
index d033b62c1..e49191ea3 100644
--- a/src/uu/chcon/src/chcon.rs
+++ b/src/uu/chcon/src/chcon.rs
@@ -6,7 +6,7 @@ use uucore::error::{UResult, USimpleError, UUsageError};
 use uucore::format_usage;
 use uucore::{display::Quotable, show_error, show_warning};
 
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use selinux::{OpaqueSecurityContext, SecurityContext};
 
 use std::borrow::Cow;
@@ -29,6 +29,7 @@ const USAGE: &str = "\
     {} [OPTION]... --reference=RFILE FILE...";
 
 pub mod options {
+    pub static HELP: &str = "help";
     pub static VERBOSE: &str = "verbose";
 
     pub static REFERENCE: &str = "reference";
@@ -65,7 +66,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         Ok(r) => r,
         Err(r) => {
             if let Error::CommandLine(r) = &r {
-                match r.kind {
+                match r.kind() {
                     clap::ErrorKind::DisplayHelp | clap::ErrorKind::DisplayVersion => {
                         println!("{}", r);
                         return Ok(());
@@ -154,12 +155,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Err(libc::EXIT_FAILURE.into())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(VERSION)
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information."),
+        )
         .arg(
             Arg::new(options::dereference::DEREFERENCE)
                 .long(options::dereference::DEREFERENCE)
@@ -303,7 +309,7 @@ struct Options {
     files: Vec<PathBuf>,
 }
 
-fn parse_command_line(config: clap::App, args: impl uucore::Args) -> Result<Options> {
+fn parse_command_line(config: clap::Command, args: impl uucore::Args) -> Result<Options> {
     let matches = config.try_get_matches_from(args)?;
 
     let verbose = matches.is_present(options::VERBOSE);
@@ -402,23 +408,21 @@ enum RecursiveMode {
 impl RecursiveMode {
     fn is_recursive(self) -> bool {
         match self {
-            RecursiveMode::NotRecursive => false,
+            Self::NotRecursive => false,
 
-            RecursiveMode::RecursiveButDoNotFollowSymLinks
-            | RecursiveMode::RecursiveAndFollowAllDirSymLinks
-            | RecursiveMode::RecursiveAndFollowArgDirSymLinks => true,
+            Self::RecursiveButDoNotFollowSymLinks
+            | Self::RecursiveAndFollowAllDirSymLinks
+            | Self::RecursiveAndFollowArgDirSymLinks => true,
         }
     }
 
     fn fts_open_options(self) -> c_int {
         match self {
-            RecursiveMode::NotRecursive | RecursiveMode::RecursiveButDoNotFollowSymLinks => {
-                fts_sys::FTS_PHYSICAL
-            }
+            Self::NotRecursive | Self::RecursiveButDoNotFollowSymLinks => fts_sys::FTS_PHYSICAL,
 
-            RecursiveMode::RecursiveAndFollowAllDirSymLinks => fts_sys::FTS_LOGICAL,
+            Self::RecursiveAndFollowAllDirSymLinks => fts_sys::FTS_LOGICAL,
 
-            RecursiveMode::RecursiveAndFollowArgDirSymLinks => {
+            Self::RecursiveAndFollowArgDirSymLinks => {
                 fts_sys::FTS_PHYSICAL | fts_sys::FTS_COMFOLLOW
             }
         }
diff --git a/src/uu/chgrp/Cargo.toml b/src/uu/chgrp/Cargo.toml
index ff60de836..d06c9adfa 100644
--- a/src/uu/chgrp/Cargo.toml
+++ b/src/uu/chgrp/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/chgrp.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "fs", "perms"] }
 
 [[bin]]
diff --git a/src/uu/chgrp/src/chgrp.rs b/src/uu/chgrp/src/chgrp.rs
index affaf86a3..d7e8baafe 100644
--- a/src/uu/chgrp/src/chgrp.rs
+++ b/src/uu/chgrp/src/chgrp.rs
@@ -13,7 +13,7 @@ use uucore::error::{FromIo, UResult, USimpleError};
 use uucore::format_usage;
 use uucore::perms::{chown_base, options, IfFrom};
 
-use clap::{App, AppSettings, Arg, ArgMatches};
+use clap::{Arg, ArgMatches, Command};
 
 use std::fs;
 use std::os::unix::fs::MetadataExt;
@@ -54,12 +54,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     chown_base(uu_app(), args, options::ARG_GROUP, parse_gid_and_uid, true)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(VERSION)
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information.")
+        )
         .arg(
             Arg::new(options::verbosity::CHANGES)
                 .short('c')
diff --git a/src/uu/chmod/Cargo.toml b/src/uu/chmod/Cargo.toml
index b2eb42574..1c52e2f2d 100644
--- a/src/uu/chmod/Cargo.toml
+++ b/src/uu/chmod/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/chmod.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs", "mode"] }
 
 [[bin]]
diff --git a/src/uu/chmod/src/chmod.rs b/src/uu/chmod/src/chmod.rs
index c2b51ae5e..25a37c372 100644
--- a/src/uu/chmod/src/chmod.rs
+++ b/src/uu/chmod/src/chmod.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) Chmoder cmode fmode fperm fref ugoa RFILE RFILE's
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs;
 use std::os::unix::fs::{MetadataExt, PermissionsExt};
 use std::path::Path;
@@ -112,12 +112,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     chmoder.chmod(&files)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::CHANGES)
                 .long(options::CHANGES)
diff --git a/src/uu/chown/Cargo.toml b/src/uu/chown/Cargo.toml
index b18310646..710a7b850 100644
--- a/src/uu/chown/Cargo.toml
+++ b/src/uu/chown/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/chown.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "fs", "perms"] }
 
 [[bin]]
diff --git a/src/uu/chown/src/chown.rs b/src/uu/chown/src/chown.rs
index 27a989847..3add9df1f 100644
--- a/src/uu/chown/src/chown.rs
+++ b/src/uu/chown/src/chown.rs
@@ -14,7 +14,7 @@ use uucore::perms::{chown_base, options, IfFrom};
 
 use uucore::error::{FromIo, UResult, USimpleError};
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 
 use std::fs;
 use std::os::unix::fs::MetadataExt;
@@ -63,12 +63,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     )
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information."),
+        )
         .arg(
             Arg::new(options::verbosity::CHANGES)
                 .short('c')
diff --git a/src/uu/chroot/Cargo.toml b/src/uu/chroot/Cargo.toml
index d6a9dd080..a46f46a90 100644
--- a/src/uu/chroot/Cargo.toml
+++ b/src/uu/chroot/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/chroot.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries"] }
 
 [[bin]]
diff --git a/src/uu/chroot/src/chroot.rs b/src/uu/chroot/src/chroot.rs
index d18264566..713336104 100644
--- a/src/uu/chroot/src/chroot.rs
+++ b/src/uu/chroot/src/chroot.rs
@@ -10,11 +10,11 @@
 mod error;
 
 use crate::error::ChrootError;
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::ffi::CString;
 use std::io::Error;
 use std::path::Path;
-use std::process::Command;
+use std::process;
 use uucore::error::{set_exit_code, UResult};
 use uucore::libc::{self, chroot, setgid, setgroups, setuid};
 use uucore::{entries, format_usage, InvalidEncodingHandling};
@@ -77,7 +77,10 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     // NOTE: Tests can only trigger code beyond this point if they're invoked with root permissions
     set_context(newroot, &matches)?;
 
-    let pstatus = match Command::new(chroot_command).args(chroot_args).status() {
+    let pstatus = match process::Command::new(chroot_command)
+        .args(chroot_args)
+        .status()
+    {
         Ok(status) => status,
         Err(e) => return Err(ChrootError::CommandFailed(command[0].to_string(), e).into()),
     };
@@ -91,12 +94,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::NEWROOT)
                 .hide(true)
diff --git a/src/uu/chroot/src/error.rs b/src/uu/chroot/src/error.rs
index ebf8f6212..69e8ac54b 100644
--- a/src/uu/chroot/src/error.rs
+++ b/src/uu/chroot/src/error.rs
@@ -55,25 +55,25 @@ impl UError for ChrootError {
 impl Display for ChrootError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {
-            ChrootError::CannotEnter(s, e) => write!(f, "cannot chroot to {}: {}", s.quote(), e,),
-            ChrootError::CommandFailed(s, e) => {
+            Self::CannotEnter(s, e) => write!(f, "cannot chroot to {}: {}", s.quote(), e,),
+            Self::CommandFailed(s, e) => {
                 write!(f, "failed to run command {}: {}", s.to_string().quote(), e,)
             }
-            ChrootError::InvalidUserspec(s) => write!(f, "invalid userspec: {}", s.quote(),),
-            ChrootError::MissingNewRoot => write!(
+            Self::InvalidUserspec(s) => write!(f, "invalid userspec: {}", s.quote(),),
+            Self::MissingNewRoot => write!(
                 f,
                 "Missing operand: NEWROOT\nTry '{} --help' for more information.",
                 uucore::execution_phrase(),
             ),
-            ChrootError::NoSuchGroup(s) => write!(f, "no such group: {}", s.maybe_quote(),),
-            ChrootError::NoSuchDirectory(s) => write!(
+            Self::NoSuchGroup(s) => write!(f, "no such group: {}", s.maybe_quote(),),
+            Self::NoSuchDirectory(s) => write!(
                 f,
                 "cannot change root directory to {}: no such directory",
                 s.quote(),
             ),
-            ChrootError::SetGidFailed(s, e) => write!(f, "cannot set gid to {}: {}", s, e),
-            ChrootError::SetGroupsFailed(e) => write!(f, "cannot set groups: {}", e),
-            ChrootError::SetUserFailed(s, e) => {
+            Self::SetGidFailed(s, e) => write!(f, "cannot set gid to {}: {}", s, e),
+            Self::SetGroupsFailed(e) => write!(f, "cannot set groups: {}", e),
+            Self::SetUserFailed(s, e) => {
                 write!(f, "cannot set user to {}: {}", s.maybe_quote(), e)
             }
         }
diff --git a/src/uu/cksum/Cargo.toml b/src/uu/cksum/Cargo.toml
index 488affbae..35ee3092b 100644
--- a/src/uu/cksum/Cargo.toml
+++ b/src/uu/cksum/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/cksum.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/cksum/src/cksum.rs b/src/uu/cksum/src/cksum.rs
index 7f7ba9ed3..e901e0820 100644
--- a/src/uu/cksum/src/cksum.rs
+++ b/src/uu/cksum/src/cksum.rs
@@ -6,7 +6,7 @@
 // file that was distributed with this source code.
 
 // spell-checker:ignore (ToDO) fname
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{self, stdin, BufReader, Read};
 use std::path::Path;
@@ -140,13 +140,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .about(SUMMARY)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FILE)
                 .hide(true)
diff --git a/src/uu/comm/Cargo.toml b/src/uu/comm/Cargo.toml
index addecbbee..aca84b209 100644
--- a/src/uu/comm/Cargo.toml
+++ b/src/uu/comm/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/comm.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/comm/src/comm.rs b/src/uu/comm/src/comm.rs
index 8064dd216..2207493d3 100644
--- a/src/uu/comm/src/comm.rs
+++ b/src/uu/comm/src/comm.rs
@@ -15,7 +15,7 @@ use uucore::error::FromIo;
 use uucore::error::UResult;
 use uucore::{format_usage, InvalidEncodingHandling};
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 
 static ABOUT: &str = "compare two sorted files line by line";
 static LONG_HELP: &str = "";
@@ -143,13 +143,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::COLUMN_1)
                 .short('1')
diff --git a/src/uu/cp/Cargo.toml b/src/uu/cp/Cargo.toml
index ffc008503..735a1fab3 100644
--- a/src/uu/cp/Cargo.toml
+++ b/src/uu/cp/Cargo.toml
@@ -19,9 +19,9 @@ edition = "2018"
 path = "src/cp.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 filetime = "0.2"
-libc = "0.2.85"
+libc = "0.2.121"
 quick-error = "2.0.1"
 selinux = { version="0.2", optional=true }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "fs", "perms", "mode"] }
diff --git a/src/uu/cp/src/cp.rs b/src/uu/cp/src/cp.rs
index a4a512d6b..d69bb705b 100644
--- a/src/uu/cp/src/cp.rs
+++ b/src/uu/cp/src/cp.rs
@@ -28,7 +28,7 @@ use winapi::um::fileapi::GetFileInformationByHandle;
 
 use std::borrow::Cow;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use filetime::FileTime;
 #[cfg(unix)]
 use libc::mkfifo;
@@ -296,7 +296,7 @@ static DEFAULT_ATTRIBUTES: &[Attribute] = &[
     Attribute::Timestamps,
 ];
 
-pub fn uu_app<'a>() -> App<'a> {
+pub fn uu_app<'a>() -> Command<'a> {
     const MODE_ARGS: &[&str] = &[
         options::LINK,
         options::REFLINK,
@@ -304,17 +304,23 @@ pub fn uu_app<'a>() -> App<'a> {
         options::ATTRIBUTES_ONLY,
         options::COPY_CONTENTS,
     ];
-    App::new(uucore::util_name())
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(options::TARGET_DIRECTORY)
              .short('t')
              .conflicts_with(options::NO_TARGET_DIRECTORY)
              .long(options::TARGET_DIRECTORY)
              .value_name(options::TARGET_DIRECTORY)
              .takes_value(true)
+             .validator(|s| {
+                 if Path::new(s).is_dir() {
+                     return Ok(());
+                 }
+                 Err(format!("'{}' is not a directory", s))
+             })
              .help("copy all SOURCE arguments into target-directory"))
         .arg(Arg::new(options::NO_TARGET_DIRECTORY)
              .short('T')
@@ -389,7 +395,7 @@ pub fn uu_app<'a>() -> App<'a> {
              .long(options::PRESERVE)
              .takes_value(true)
              .multiple_occurrences(true)
-             .use_delimiter(true)
+             .use_value_delimiter(true)
              .possible_values(PRESERVABLE_ATTRIBUTES)
              .min_values(0)
              .value_name("ATTR_LIST")
@@ -469,7 +475,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
             LONG_HELP,
             backup_control::BACKUP_CONTROL_LONG_HELP
         ))
-        .get_matches_from(args);
+        .try_get_matches_from(args)?;
 
     let options = Options::from_matches(&matches)?;
 
@@ -1087,8 +1093,8 @@ fn copy_directory(
 impl OverwriteMode {
     fn verify(&self, path: &Path) -> CopyResult<()> {
         match *self {
-            OverwriteMode::NoClobber => Err(Error::NotAllFilesCopied),
-            OverwriteMode::Interactive(_) => {
+            Self::NoClobber => Err(Error::NotAllFilesCopied),
+            Self::Interactive(_) => {
                 if prompt_yes!("{}: overwrite {}? ", uucore::util_name(), path.quote()) {
                     Ok(())
                 } else {
@@ -1098,7 +1104,7 @@ impl OverwriteMode {
                     )))
                 }
             }
-            OverwriteMode::Clobber(_) => Ok(()),
+            Self::Clobber(_) => Ok(()),
         }
     }
 }
diff --git a/src/uu/csplit/Cargo.toml b/src/uu/csplit/Cargo.toml
index 89fc118dd..f956db9fc 100644
--- a/src/uu/csplit/Cargo.toml
+++ b/src/uu/csplit/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/csplit.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 thiserror = "1.0"
 regex = "1.0.0"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "fs"] }
diff --git a/src/uu/csplit/src/csplit.rs b/src/uu/csplit/src/csplit.rs
index 7793a8637..a0b739935 100644
--- a/src/uu/csplit/src/csplit.rs
+++ b/src/uu/csplit/src/csplit.rs
@@ -12,7 +12,7 @@ use std::{
     io::{BufRead, BufWriter, Write},
 };
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use regex::Regex;
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult};
@@ -746,12 +746,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(SUMMARY)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::SUFFIX_FORMAT)
                 .short('b')
diff --git a/src/uu/cut/Cargo.toml b/src/uu/cut/Cargo.toml
index 302f8f0c1..fb8e75470 100644
--- a/src/uu/cut/Cargo.toml
+++ b/src/uu/cut/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/cut.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 memchr = "2"
 bstr = "0.2"
diff --git a/src/uu/cut/src/cut.rs b/src/uu/cut/src/cut.rs
index ce82a2737..2264f4f26 100644
--- a/src/uu/cut/src/cut.rs
+++ b/src/uu/cut/src/cut.rs
@@ -11,7 +11,7 @@
 extern crate uucore;
 
 use bstr::io::BufReadExt;
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{stdin, stdout, BufReader, BufWriter, Read, Write};
 use std::path::Path;
@@ -533,14 +533,14 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
         .after_help(LONG_HELP)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BYTES)
                 .short('b')
diff --git a/src/uu/date/Cargo.toml b/src/uu/date/Cargo.toml
index 793022992..c423bbe0f 100644
--- a/src/uu/date/Cargo.toml
+++ b/src/uu/date/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/date.rs"
 
 [dependencies]
 chrono = "^0.4.11"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [target.'cfg(unix)'.dependencies]
diff --git a/src/uu/date/src/date.rs b/src/uu/date/src/date.rs
index 18e06aef4..8946768d5 100644
--- a/src/uu/date/src/date.rs
+++ b/src/uu/date/src/date.rs
@@ -11,7 +11,7 @@
 use chrono::{DateTime, FixedOffset, Local, Offset, Utc};
 #[cfg(windows)]
 use chrono::{Datelike, Timelike};
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 #[cfg(all(unix, not(target_os = "macos"), not(target_os = "redox")))]
 use libc::{clock_settime, timespec, CLOCK_REALTIME};
 use std::fs::File;
@@ -254,12 +254,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_DATE)
                 .short('d')
diff --git a/src/uu/dd/Cargo.toml b/src/uu/dd/Cargo.toml
index 70a1bfda7..54723ed30 100644
--- a/src/uu/dd/Cargo.toml
+++ b/src/uu/dd/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/dd.rs"
 
 [dependencies]
 byte-unit = "4.0"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 gcd = "2.0"
 libc = "0.2"
 uucore = { version=">=0.0.8", package="uucore", path="../../uucore" }
diff --git a/src/uu/dd/src/datastructures.rs b/src/uu/dd/src/datastructures.rs
index 067058bbe..6529f6602 100644
--- a/src/uu/dd/src/datastructures.rs
+++ b/src/uu/dd/src/datastructures.rs
@@ -4,7 +4,7 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
-// spell-checker:ignore ctable, outfile
+// spell-checker:ignore ctable, outfile, iseek, oseek
 
 use std::error::Error;
 
@@ -120,6 +120,8 @@ pub mod options {
     pub const COUNT: &str = "count";
     pub const SKIP: &str = "skip";
     pub const SEEK: &str = "seek";
+    pub const ISEEK: &str = "iseek";
+    pub const OSEEK: &str = "oseek";
     pub const STATUS: &str = "status";
     pub const CONV: &str = "conv";
     pub const IFLAG: &str = "iflag";
diff --git a/src/uu/dd/src/dd.rs b/src/uu/dd/src/dd.rs
index d8bc3acd3..cdfcdb732 100644
--- a/src/uu/dd/src/dd.rs
+++ b/src/uu/dd/src/dd.rs
@@ -5,7 +5,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore fname, tname, fpath, specfile, testfile, unspec, ifile, ofile, outfile, fullblock, urand, fileio, atoe, atoibm, behaviour, bmax, bremain, cflags, creat, ctable, ctty, datastructures, doesnt, etoa, fileout, fname, gnudd, iconvflags, nocache, noctty, noerror, nofollow, nolinks, nonblock, oconvflags, outfile, parseargs, rlen, rmax, rremain, rsofar, rstat, sigusr, wlen, wstat seekable
+// spell-checker:ignore fname, tname, fpath, specfile, testfile, unspec, ifile, ofile, outfile, fullblock, urand, fileio, atoe, atoibm, behaviour, bmax, bremain, cflags, creat, ctable, ctty, datastructures, doesnt, etoa, fileout, fname, gnudd, iconvflags, iseek, nocache, noctty, noerror, nofollow, nolinks, nonblock, oconvflags, oseek, outfile, parseargs, rlen, rmax, rremain, rsofar, rstat, sigusr, wlen, wstat seekable
 
 mod datastructures;
 use datastructures::*;
@@ -34,7 +34,7 @@ use std::sync::mpsc;
 use std::thread;
 use std::time;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use gcd::Gcd;
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult};
@@ -60,7 +60,9 @@ impl Input<io::Stdin> {
         let print_level = parseargs::parse_status_level(matches)?;
         let cflags = parseargs::parse_conv_flag_input(matches)?;
         let iflags = parseargs::parse_iflags(matches)?;
-        let skip = parseargs::parse_skip_amt(&ibs, &iflags, matches)?;
+        let skip = parseargs::parse_seek_skip_amt(&ibs, iflags.skip_bytes, matches, options::SKIP)?;
+        let iseek =
+            parseargs::parse_seek_skip_amt(&ibs, iflags.skip_bytes, matches, options::ISEEK)?;
         let count = parseargs::parse_count(&iflags, matches)?;
 
         let mut i = Self {
@@ -73,7 +75,9 @@ impl Input<io::Stdin> {
             iflags,
         };
 
-        if let Some(amt) = skip {
+        // The --skip and --iseek flags are additive. On a stream, they discard bytes.
+        let amt = skip.unwrap_or(0) + iseek.unwrap_or(0);
+        if amt > 0 {
             if let Err(e) = i.read_skip(amt) {
                 if let io::ErrorKind::UnexpectedEof = e.kind() {
                     show_error!("'standard input': cannot skip to specified offset");
@@ -131,7 +135,9 @@ impl Input<File> {
         let print_level = parseargs::parse_status_level(matches)?;
         let cflags = parseargs::parse_conv_flag_input(matches)?;
         let iflags = parseargs::parse_iflags(matches)?;
-        let skip = parseargs::parse_skip_amt(&ibs, &iflags, matches)?;
+        let skip = parseargs::parse_seek_skip_amt(&ibs, iflags.skip_bytes, matches, options::SKIP)?;
+        let iseek =
+            parseargs::parse_seek_skip_amt(&ibs, iflags.skip_bytes, matches, options::ISEEK)?;
         let count = parseargs::parse_count(&iflags, matches)?;
 
         if let Some(fname) = matches.value_of(options::INFILE) {
@@ -148,7 +154,9 @@ impl Input<File> {
                     .map_err_context(|| "failed to open input file".to_string())?
             };
 
-            if let Some(amt) = skip {
+            // The --skip and --iseek flags are additive. On a file, they seek.
+            let amt = skip.unwrap_or(0) + iseek.unwrap_or(0);
+            if amt > 0 {
                 src.seek(io::SeekFrom::Start(amt))
                     .map_err_context(|| "failed to seek in input file".to_string())?;
             }
@@ -292,12 +300,16 @@ impl OutputTrait for Output<io::Stdout> {
         let obs = parseargs::parse_obs(matches)?;
         let cflags = parseargs::parse_conv_flag_output(matches)?;
         let oflags = parseargs::parse_oflags(matches)?;
-        let seek = parseargs::parse_seek_amt(&obs, &oflags, matches)?;
+        let seek = parseargs::parse_seek_skip_amt(&obs, oflags.seek_bytes, matches, options::SEEK)?;
+        let oseek =
+            parseargs::parse_seek_skip_amt(&obs, oflags.seek_bytes, matches, options::OSEEK)?;
 
         let mut dst = io::stdout();
 
+        // The --seek and --oseek flags are additive.
+        let amt = seek.unwrap_or(0) + oseek.unwrap_or(0);
         // stdout is not seekable, so we just write null bytes.
-        if let Some(amt) = seek {
+        if amt > 0 {
             io::copy(&mut io::repeat(0u8).take(amt as u64), &mut dst)
                 .map_err_context(|| String::from("write error"))?;
         }
@@ -508,7 +520,9 @@ impl OutputTrait for Output<File> {
         let obs = parseargs::parse_obs(matches)?;
         let cflags = parseargs::parse_conv_flag_output(matches)?;
         let oflags = parseargs::parse_oflags(matches)?;
-        let seek = parseargs::parse_seek_amt(&obs, &oflags, matches)?;
+        let seek = parseargs::parse_seek_skip_amt(&obs, oflags.seek_bytes, matches, options::SEEK)?;
+        let oseek =
+            parseargs::parse_seek_skip_amt(&obs, oflags.seek_bytes, matches, options::OSEEK)?;
 
         if let Some(fname) = matches.value_of(options::OUTFILE) {
             let mut dst = open_dst(Path::new(&fname), &cflags, &oflags)
@@ -522,7 +536,9 @@ impl OutputTrait for Output<File> {
             // Instead, we suppress the error by calling
             // `Result::ok()`. This matches the behavior of GNU `dd`
             // when given the command-line argument `of=/dev/null`.
-            let i = seek.unwrap_or(0);
+
+            // The --seek and --oseek flags are additive.
+            let i = seek.unwrap_or(0) + oseek.unwrap_or(0);
             if !cflags.notrunc {
                 dst.set_len(i).ok();
             }
@@ -730,11 +746,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::INFILE)
                 .long(options::INFILE)
@@ -807,6 +823,24 @@ pub fn uu_app<'a>() -> App<'a> {
                 .value_name("N")
                 .help("(alternatively seek=N) seeks N obs-sized records into output before beginning copy/convert operations. See oflag=seek_bytes if seeking N bytes is preferred. Multiplier strings permitted.")
         )
+        .arg(
+            Arg::new(options::ISEEK)
+                .long(options::ISEEK)
+                .overrides_with(options::ISEEK)
+                .takes_value(true)
+                .require_equals(true)
+                .value_name("N")
+                .help("(alternatively iseek=N) seeks N obs-sized records into input before beginning copy/convert operations. See iflag=seek_bytes if seeking N bytes is preferred. Multiplier strings permitted.")
+        )
+        .arg(
+            Arg::new(options::OSEEK)
+                .long(options::OSEEK)
+                .overrides_with(options::OSEEK)
+                .takes_value(true)
+                .require_equals(true)
+                .value_name("N")
+                .help("(alternatively oseek=N) seeks N obs-sized records into output before beginning copy/convert operations. See oflag=seek_bytes if seeking N bytes is preferred. Multiplier strings permitted.")
+        )
         .arg(
             Arg::new(options::COUNT)
                 .long(options::COUNT)
@@ -846,8 +880,8 @@ Printing performance stats is also triggered by the INFO signal (where supported
                 .long(options::CONV)
                 .takes_value(true)
                 .multiple_occurrences(true)
-                .use_delimiter(true)
-                .require_delimiter(true)
+                .use_value_delimiter(true)
+                .require_value_delimiter(true)
                 .multiple_values(true)
                 .require_equals(true)
                 .value_name("CONV")
@@ -887,8 +921,8 @@ Conversion Flags:
                 .long(options::IFLAG)
                 .takes_value(true)
                 .multiple_occurrences(true)
-                .use_delimiter(true)
-                .require_delimiter(true)
+                .use_value_delimiter(true)
+                .require_value_delimiter(true)
                 .multiple_values(true)
                 .require_equals(true)
                 .value_name("FLAG")
@@ -917,8 +951,8 @@ General-Flags
                 .long(options::OFLAG)
                 .takes_value(true)
                 .multiple_occurrences(true)
-                .use_delimiter(true)
-                .require_delimiter(true)
+                .use_value_delimiter(true)
+                .require_value_delimiter(true)
                 .multiple_values(true)
                 .require_equals(true)
                 .value_name("FLAG")
diff --git a/src/uu/dd/src/parseargs.rs b/src/uu/dd/src/parseargs.rs
index d8639fca9..8f2f10e70 100644
--- a/src/uu/dd/src/parseargs.rs
+++ b/src/uu/dd/src/parseargs.rs
@@ -4,7 +4,7 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
-// spell-checker:ignore ctty, ctable, iconvflags, oconvflags parseargs
+// spell-checker:ignore ctty, ctable, iseek, oseek, iconvflags, oconvflags parseargs
 
 #[cfg(test)]
 mod unit_tests;
@@ -100,16 +100,16 @@ impl std::fmt::Display for ParseError {
             Self::StatusLevelNotRecognized(arg) => {
                 write!(f, "status=LEVEL not recognized -> {}", arg)
             }
-            ParseError::BsOutOfRange => {
+            Self::BsOutOfRange => {
                 write!(f, "bs=N cannot fit into memory")
             }
-            ParseError::IbsOutOfRange => {
+            Self::IbsOutOfRange => {
                 write!(f, "ibs=N cannot fit into memory")
             }
-            ParseError::ObsOutOfRange => {
+            Self::ObsOutOfRange => {
                 write!(f, "obs=N cannot fit into memory")
             }
-            ParseError::CbsOutOfRange => {
+            Self::CbsOutOfRange => {
                 write!(f, "cbs=N cannot fit into memory")
             }
             Self::Unimplemented(arg) => {
@@ -740,15 +740,15 @@ pub fn parse_oflags(matches: &Matches) -> Result<OFlags, ParseError> {
     Ok(oflags)
 }
 
-/// Parse the amount of the input file to skip.
-pub fn parse_skip_amt(
+pub fn parse_seek_skip_amt(
     ibs: &usize,
-    iflags: &IFlags,
+    bytes: bool,
     matches: &Matches,
+    option: &str,
 ) -> Result<Option<u64>, ParseError> {
-    if let Some(amt) = matches.value_of(options::SKIP) {
+    if let Some(amt) = matches.value_of(option) {
         let n = parse_bytes_with_opt_multiplier(amt)?;
-        if iflags.skip_bytes {
+        if bytes {
             Ok(Some(n))
         } else {
             Ok(Some(*ibs as u64 * n))
@@ -758,24 +758,6 @@ pub fn parse_skip_amt(
     }
 }
 
-/// Parse the amount of the output file to seek.
-pub fn parse_seek_amt(
-    obs: &usize,
-    oflags: &OFlags,
-    matches: &Matches,
-) -> Result<Option<u64>, ParseError> {
-    if let Some(amt) = matches.value_of(options::SEEK) {
-        let n = parse_bytes_with_opt_multiplier(amt)?;
-        if oflags.seek_bytes {
-            Ok(Some(n))
-        } else {
-            Ok(Some(*obs as u64 * n))
-        }
-    } else {
-        Ok(None)
-    }
-}
-
 /// Parse the value of count=N and the type of N implied by iflags
 pub fn parse_count(iflags: &IFlags, matches: &Matches) -> Result<Option<CountType>, ParseError> {
     if let Some(amt) = matches.value_of(options::COUNT) {
diff --git a/src/uu/dd/src/parseargs/unit_tests.rs b/src/uu/dd/src/parseargs/unit_tests.rs
index 1e5b4b930..f5d71959a 100644
--- a/src/uu/dd/src/parseargs/unit_tests.rs
+++ b/src/uu/dd/src/parseargs/unit_tests.rs
@@ -1,4 +1,4 @@
-// spell-checker:ignore fname, tname, fpath, specfile, testfile, unspec, ifile, ofile, outfile, fullblock, urand, fileio, atoe, atoibm, behaviour, bmax, bremain, btotal, cflags, creat, ctable, ctty, datastructures, doesnt, etoa, fileout, fname, gnudd, iconvflags, nocache, noctty, noerror, nofollow, nolinks, nonblock, oconvflags, outfile, parseargs, rlen, rmax, rposition, rremain, rsofar, rstat, sigusr, sigval, wlen, wstat
+// spell-checker:ignore fname, tname, fpath, specfile, testfile, unspec, ifile, ofile, outfile, fullblock, urand, fileio, atoe, atoibm, behaviour, bmax, bremain, btotal, cflags, creat, ctable, ctty, datastructures, doesnt, etoa, fileout, fname, gnudd, iconvflags, iseek, nocache, noctty, noerror, nofollow, nolinks, nonblock, oconvflags, oseek, outfile, parseargs, rlen, rmax, rposition, rremain, rsofar, rstat, sigusr, sigval, wlen, wstat
 
 use super::*;
 
@@ -112,6 +112,8 @@ fn test_all_top_level_args_no_leading_dashes() {
         String::from("count=2"),
         String::from("skip=2"),
         String::from("seek=2"),
+        String::from("iseek=2"),
+        String::from("oseek=2"),
         String::from("status=progress"),
         String::from("conv=ascii,ucase"),
         String::from("iflag=count_bytes,skip_bytes"),
@@ -140,13 +142,25 @@ fn test_all_top_level_args_no_leading_dashes() {
     );
     assert_eq!(
         200,
-        parse_skip_amt(&100, &IFlags::default(), &matches)
+        parse_seek_skip_amt(&100, IFlags::default().skip_bytes, &matches, options::SKIP)
             .unwrap()
             .unwrap()
     );
     assert_eq!(
         200,
-        parse_seek_amt(&100, &OFlags::default(), &matches)
+        parse_seek_skip_amt(&100, OFlags::default().seek_bytes, &matches, options::SEEK)
+            .unwrap()
+            .unwrap()
+    );
+    assert_eq!(
+        200,
+        parse_seek_skip_amt(&100, IFlags::default().skip_bytes, &matches, options::ISEEK)
+            .unwrap()
+            .unwrap()
+    );
+    assert_eq!(
+        200,
+        parse_seek_skip_amt(&100, OFlags::default().seek_bytes, &matches, options::OSEEK)
             .unwrap()
             .unwrap()
     );
@@ -197,6 +211,8 @@ fn test_all_top_level_args_with_leading_dashes() {
         String::from("--count=2"),
         String::from("--skip=2"),
         String::from("--seek=2"),
+        String::from("--iseek=2"),
+        String::from("--oseek=2"),
         String::from("--status=progress"),
         String::from("--conv=ascii,ucase"),
         String::from("--iflag=count_bytes,skip_bytes"),
@@ -225,13 +241,25 @@ fn test_all_top_level_args_with_leading_dashes() {
     );
     assert_eq!(
         200,
-        parse_skip_amt(&100, &IFlags::default(), &matches)
+        parse_seek_skip_amt(&100, IFlags::default().skip_bytes, &matches, options::SKIP)
             .unwrap()
             .unwrap()
     );
     assert_eq!(
         200,
-        parse_seek_amt(&100, &OFlags::default(), &matches)
+        parse_seek_skip_amt(&100, OFlags::default().seek_bytes, &matches, options::SEEK)
+            .unwrap()
+            .unwrap()
+    );
+    assert_eq!(
+        200,
+        parse_seek_skip_amt(&100, IFlags::default().skip_bytes, &matches, options::ISEEK)
+            .unwrap()
+            .unwrap()
+    );
+    assert_eq!(
+        200,
+        parse_seek_skip_amt(&100, OFlags::default().seek_bytes, &matches, options::OSEEK)
             .unwrap()
             .unwrap()
     );
@@ -303,10 +331,10 @@ fn test_status_level_noxfer() {
 fn test_multiple_flags_options() {
     let args = vec![
         String::from("dd"),
-        String::from("--iflag=fullblock,directory"),
+        String::from("--iflag=fullblock,count_bytes"),
         String::from("--iflag=skip_bytes"),
-        String::from("--oflag=direct"),
-        String::from("--oflag=dsync"),
+        String::from("--oflag=append"),
+        String::from("--oflag=seek_bytes"),
         String::from("--conv=ascii,ucase"),
         String::from("--conv=unblock"),
     ];
@@ -315,13 +343,13 @@ fn test_multiple_flags_options() {
     // iflag
     let iflags = parse_flag_list::<Flag>(options::IFLAG, &matches).unwrap();
     assert_eq!(
-        vec![Flag::FullBlock, Flag::Directory, Flag::SkipBytes],
+        vec![Flag::FullBlock, Flag::CountBytes, Flag::SkipBytes],
         iflags
     );
 
     // oflag
     let oflags = parse_flag_list::<Flag>(options::OFLAG, &matches).unwrap();
-    assert_eq!(vec![Flag::Direct, Flag::Dsync], oflags);
+    assert_eq!(vec![Flag::Append, Flag::SeekBytes], oflags);
 
     // conv
     let conv = parse_flag_list::<ConvFlag>(options::CONV, &matches).unwrap();
@@ -349,6 +377,10 @@ fn test_override_multiple_options() {
         String::from("--skip=2"),
         String::from("--seek=0"),
         String::from("--seek=2"),
+        String::from("--iseek=0"),
+        String::from("--iseek=2"),
+        String::from("--oseek=0"),
+        String::from("--oseek=2"),
         String::from("--status=none"),
         String::from("--status=noxfer"),
         String::from("--count=512"),
@@ -381,7 +413,7 @@ fn test_override_multiple_options() {
     // skip
     assert_eq!(
         200,
-        parse_skip_amt(&100, &IFlags::default(), &matches)
+        parse_seek_skip_amt(&100, IFlags::default().skip_bytes, &matches, options::SKIP)
             .unwrap()
             .unwrap()
     );
@@ -389,7 +421,23 @@ fn test_override_multiple_options() {
     // seek
     assert_eq!(
         200,
-        parse_seek_amt(&100, &OFlags::default(), &matches)
+        parse_seek_skip_amt(&100, OFlags::default().seek_bytes, &matches, options::SEEK)
+            .unwrap()
+            .unwrap()
+    );
+
+    // iseek
+    assert_eq!(
+        200,
+        parse_seek_skip_amt(&100, IFlags::default().skip_bytes, &matches, options::ISEEK)
+            .unwrap()
+            .unwrap()
+    );
+
+    // oseek
+    assert_eq!(
+        200,
+        parse_seek_skip_amt(&100, OFlags::default().seek_bytes, &matches, options::OSEEK)
             .unwrap()
             .unwrap()
     );
@@ -685,7 +733,7 @@ mod test_64bit_arch {
 #[test]
 #[should_panic]
 fn test_overflow_panic() {
-    let bs_str = format!("{}KiB", usize::MAX);
+    let bs_str = format!("{}KiB", u64::MAX);
 
     parse_bytes_with_opt_multiplier(&bs_str).unwrap();
 }
diff --git a/src/uu/df/Cargo.toml b/src/uu/df/Cargo.toml
index 29f32c6cf..3e9010f1e 100644
--- a/src/uu/df/Cargo.toml
+++ b/src/uu/df/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/df.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 number_prefix = "0.4"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["libc", "fsext"] }
 
diff --git a/src/uu/df/src/df.rs b/src/uu/df/src/df.rs
index 338648e10..934a40a3d 100644
--- a/src/uu/df/src/df.rs
+++ b/src/uu/df/src/df.rs
@@ -15,7 +15,7 @@ use uucore::error::{UResult, USimpleError};
 use uucore::format_usage;
 use uucore::fsext::{read_fs_list, MountInfo};
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 
 use std::fmt;
 use std::path::Path;
@@ -29,9 +29,9 @@ static ABOUT: &str = "Show information about the file system on which each FILE
                       or all file systems by default.";
 const USAGE: &str = "{} [OPTION]... [FILE]...";
 
+static OPT_HELP: &str = "help";
 static OPT_ALL: &str = "all";
 static OPT_BLOCKSIZE: &str = "blocksize";
-static OPT_DIRECT: &str = "direct";
 static OPT_TOTAL: &str = "total";
 static OPT_HUMAN_READABLE: &str = "human-readable";
 static OPT_HUMAN_READABLE_2: &str = "human-readable-2";
@@ -316,12 +316,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(OPT_HELP)
+                .long(OPT_HELP)
+                .help("Print help information."),
+        )
         .arg(
             Arg::new(OPT_ALL)
                 .short('a')
@@ -338,11 +343,6 @@ pub fn uu_app<'a>() -> App<'a> {
                      '-BM' prints sizes in units of 1,048,576 bytes",
                 ),
         )
-        .arg(
-            Arg::new(OPT_DIRECT)
-                .long("direct")
-                .help("show statistics for a file instead of mount point"),
-        )
         .arg(
             Arg::new(OPT_TOTAL)
                 .long("total")
@@ -385,7 +385,7 @@ pub fn uu_app<'a>() -> App<'a> {
             Arg::new(OPT_OUTPUT)
                 .long("output")
                 .takes_value(true)
-                .use_delimiter(true)
+                .use_value_delimiter(true)
                 .possible_values(OUTPUT_FIELD_LIST)
                 .default_missing_values(&OUTPUT_FIELD_LIST)
                 .default_values(&["source", "size", "used", "avail", "pcent", "target"])
@@ -428,7 +428,7 @@ pub fn uu_app<'a>() -> App<'a> {
                 .long("exclude-type")
                 .allow_invalid_utf8(true)
                 .takes_value(true)
-                .use_delimiter(true)
+                .use_value_delimiter(true)
                 .multiple_occurrences(true)
                 .help("limit listing to file systems not of type TYPE"),
         )
diff --git a/src/uu/df/src/table.rs b/src/uu/df/src/table.rs
index a126876dd..00fe31caf 100644
--- a/src/uu/df/src/table.rs
+++ b/src/uu/df/src/table.rs
@@ -39,8 +39,8 @@ pub(crate) struct Row {
     /// Number of used bytes.
     bytes_used: u64,
 
-    /// Number of free bytes.
-    bytes_free: u64,
+    /// Number of available bytes.
+    bytes_avail: u64,
 
     /// Percentage of bytes that are used, given as a float between 0 and 1.
     ///
@@ -78,7 +78,7 @@ impl Row {
             fs_mount: "-".into(),
             bytes: 0,
             bytes_used: 0,
-            bytes_free: 0,
+            bytes_avail: 0,
             bytes_usage: None,
             #[cfg(target_os = "macos")]
             bytes_capacity: None,
@@ -106,7 +106,7 @@ impl AddAssign for Row {
             fs_mount: "-".into(),
             bytes,
             bytes_used,
-            bytes_free: self.bytes_free + rhs.bytes_free,
+            bytes_avail: self.bytes_avail + rhs.bytes_avail,
             bytes_usage: if bytes == 0 {
                 None
             } else {
@@ -139,7 +139,6 @@ impl From<Filesystem> for Row {
             blocksize,
             blocks,
             bfree,
-            #[cfg(target_os = "macos")]
             bavail,
             files,
             ffree,
@@ -151,7 +150,7 @@ impl From<Filesystem> for Row {
             fs_mount: mount_dir,
             bytes: blocksize * blocks,
             bytes_used: blocksize * (blocks - bfree),
-            bytes_free: blocksize * bfree,
+            bytes_avail: blocksize * bavail,
             bytes_usage: if blocks == 0 {
                 None
             } else {
@@ -236,7 +235,7 @@ impl fmt::Display for DisplayRow<'_> {
                 Column::Source => write!(f, "{0: <16} ", self.row.fs_device)?,
                 Column::Size => write!(f, "{0: >12} ", self.scaled(self.row.bytes)?)?,
                 Column::Used => write!(f, "{0: >12} ", self.scaled(self.row.bytes_used)?)?,
-                Column::Avail => write!(f, "{0: >12} ", self.scaled(self.row.bytes_free)?)?,
+                Column::Avail => write!(f, "{0: >12} ", self.scaled(self.row.bytes_avail)?)?,
                 Column::Pcent => {
                     write!(f, "{0: >5} ", DisplayRow::percentage(self.row.bytes_usage))?;
                 }
@@ -413,7 +412,7 @@ mod tests {
 
             bytes: 100,
             bytes_used: 25,
-            bytes_free: 75,
+            bytes_avail: 75,
             bytes_usage: Some(0.25),
 
             #[cfg(target_os = "macos")]
@@ -444,7 +443,7 @@ mod tests {
 
             bytes: 100,
             bytes_used: 25,
-            bytes_free: 75,
+            bytes_avail: 75,
             bytes_usage: Some(0.25),
 
             #[cfg(target_os = "macos")]
@@ -475,7 +474,7 @@ mod tests {
 
             bytes: 100,
             bytes_used: 25,
-            bytes_free: 75,
+            bytes_avail: 75,
             bytes_usage: Some(0.25),
 
             #[cfg(target_os = "macos")]
@@ -506,7 +505,7 @@ mod tests {
 
             bytes: 4000,
             bytes_used: 1000,
-            bytes_free: 3000,
+            bytes_avail: 3000,
             bytes_usage: Some(0.25),
 
             #[cfg(target_os = "macos")]
@@ -537,7 +536,7 @@ mod tests {
 
             bytes: 4096,
             bytes_used: 1024,
-            bytes_free: 3072,
+            bytes_avail: 3072,
             bytes_usage: Some(0.25),
 
             #[cfg(target_os = "macos")]
@@ -567,7 +566,7 @@ mod tests {
 
             bytes: 100,
             bytes_used: 25,
-            bytes_free: 75,
+            bytes_avail: 75,
             bytes_usage: Some(0.251),
 
             #[cfg(target_os = "macos")]
diff --git a/src/uu/dircolors/Cargo.toml b/src/uu/dircolors/Cargo.toml
index 28a520eef..ebc9d5cd9 100644
--- a/src/uu/dircolors/Cargo.toml
+++ b/src/uu/dircolors/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/dircolors.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 glob = "0.3.0"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/dircolors/src/dircolors.rs b/src/uu/dircolors/src/dircolors.rs
index dcc832ece..c76dbc0c1 100644
--- a/src/uu/dircolors/src/dircolors.rs
+++ b/src/uu/dircolors/src/dircolors.rs
@@ -13,7 +13,7 @@ use std::env;
 use std::fs::File;
 use std::io::{BufRead, BufReader};
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::display::Quotable;
 use uucore::error::{UResult, USimpleError, UUsageError};
 
@@ -154,13 +154,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(SUMMARY)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BOURNE_SHELL)
                 .long("sh")
diff --git a/src/uu/dirname/Cargo.toml b/src/uu/dirname/Cargo.toml
index e3c7ee2e8..3c7162a0d 100644
--- a/src/uu/dirname/Cargo.toml
+++ b/src/uu/dirname/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/dirname.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/dirname/src/dirname.rs b/src/uu/dirname/src/dirname.rs
index ad370aacf..030c3981c 100644
--- a/src/uu/dirname/src/dirname.rs
+++ b/src/uu/dirname/src/dirname.rs
@@ -5,7 +5,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::path::Path;
 use uucore::display::print_verbatim;
 use uucore::error::{UResult, UUsageError};
@@ -76,12 +76,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .about(ABOUT)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::ZERO)
                 .long(options::ZERO)
diff --git a/src/uu/du/Cargo.toml b/src/uu/du/Cargo.toml
index a6af1a3ae..73fa5e3a5 100644
--- a/src/uu/du/Cargo.toml
+++ b/src/uu/du/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/du.rs"
 
 [dependencies]
 chrono = "^0.4.11"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [target.'cfg(target_os = "windows")'.dependencies]
diff --git a/src/uu/du/src/du.rs b/src/uu/du/src/du.rs
index 0bb1abf4a..0690c6299 100644
--- a/src/uu/du/src/du.rs
+++ b/src/uu/du/src/du.rs
@@ -10,7 +10,7 @@ extern crate uucore;
 
 use chrono::prelude::DateTime;
 use chrono::Local;
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::collections::HashSet;
 use std::env;
 use std::fs;
@@ -47,6 +47,7 @@ use winapi::um::winbase::GetFileInformationByHandleEx;
 use winapi::um::winnt::{FILE_ID_128, ULONGLONG};
 
 mod options {
+    pub const HELP: &str = "help";
     pub const NULL: &str = "0";
     pub const ALL: &str = "all";
     pub const APPARENT_SIZE: &str = "apparent-size";
@@ -617,13 +618,18 @@ fn parse_depth(max_depth_str: Option<&str>, summarize: bool) -> UResult<Option<u
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(SUMMARY)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information.")
+        )
         .arg(
             Arg::new(options::ALL)
                 .short('a')
diff --git a/src/uu/echo/Cargo.toml b/src/uu/echo/Cargo.toml
index 8b8ba0819..fcfaec160 100644
--- a/src/uu/echo/Cargo.toml
+++ b/src/uu/echo/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/echo.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/echo/src/echo.rs b/src/uu/echo/src/echo.rs
index 54a606c31..d2de30cb1 100644
--- a/src/uu/echo/src/echo.rs
+++ b/src/uu/echo/src/echo.rs
@@ -6,7 +6,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::io::{self, Write};
 use std::iter::Peekable;
 use std::str::Chars;
@@ -126,15 +126,15 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         .map_err_context(|| "could not write to stdout".to_string())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         // TrailingVarArg specifies the final positional argument is a VarArg
         // and it doesn't attempts the parse any further args.
         // Final argument must have multiple(true) or the usage string equivalent.
-        .setting(AppSettings::TrailingVarArg)
-        .setting(AppSettings::AllowHyphenValues)
-        .setting(AppSettings::InferLongArgs)
+        .trailing_var_arg(true)
+        .allow_hyphen_values(true)
+        .infer_long_args(true)
         .version(crate_version!())
         .about(SUMMARY)
         .after_help(AFTER_HELP)
diff --git a/src/uu/env/Cargo.toml b/src/uu/env/Cargo.toml
index f5afaa896..2b1c5f30e 100644
--- a/src/uu/env/Cargo.toml
+++ b/src/uu/env/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/env.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 rust-ini = "0.17.0"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/env/src/env.rs b/src/uu/env/src/env.rs
index 136100413..b78b5f224 100644
--- a/src/uu/env/src/env.rs
+++ b/src/uu/env/src/env.rs
@@ -16,13 +16,13 @@ extern crate clap;
 #[macro_use]
 extern crate uucore;
 
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use ini::Ini;
 use std::borrow::Cow;
 use std::env;
 use std::io::{self, Write};
 use std::iter::Iterator;
-use std::process::Command;
+use std::process;
 use uucore::display::Quotable;
 use uucore::error::{UResult, USimpleError, UUsageError};
 use uucore::format_usage;
@@ -121,15 +121,15 @@ fn build_command<'a, 'b>(args: &'a mut Vec<&'b str>) -> (Cow<'b, str>, &'a [&'b
     (progname, &args[..])
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(crate_name!())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(crate_name!())
         .version(crate_version!())
         .author(crate_authors!())
         .about(crate_description!())
         .override_usage(format_usage(USAGE))
         .after_help(AFTER_HELP)
-        .setting(AppSettings::AllowExternalSubcommands)
-        .setting(AppSettings::InferLongArgs)
+        .allow_external_subcommands(true)
+        .infer_long_args(true)
         .arg(Arg::new("ignore-environment")
             .short('i')
             .long("ignore-environment")
@@ -307,7 +307,7 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
          * standard library contains many checks and fail-safes to ensure the process ends up being
          * created. This is much simpler than dealing with the hassles of calling execvp directly.
          */
-        match Command::new(&*prog).args(args).status() {
+        match process::Command::new(&*prog).args(args).status() {
             Ok(exit) if !exit.success() => return Err(exit.code().unwrap().into()),
             Err(ref err) if err.kind() == io::ErrorKind::NotFound => return Err(127.into()),
             Err(_) => return Err(126.into()),
diff --git a/src/uu/expand/Cargo.toml b/src/uu/expand/Cargo.toml
index ba2cdd317..053a2a530 100644
--- a/src/uu/expand/Cargo.toml
+++ b/src/uu/expand/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/expand.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 unicode-width = "0.1.5"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/expand/src/expand.rs b/src/uu/expand/src/expand.rs
index c2bf98093..b9d9309cd 100644
--- a/src/uu/expand/src/expand.rs
+++ b/src/uu/expand/src/expand.rs
@@ -12,7 +12,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::fs::File;
 use std::io::{stdin, stdout, BufRead, BufReader, BufWriter, Read, Write};
 use std::str::from_utf8;
@@ -176,13 +176,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     expand(&Options::new(&matches)).map_err_context(|| "failed to write output".to_string())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::INITIAL)
                 .long(options::INITIAL)
diff --git a/src/uu/expr/Cargo.toml b/src/uu/expr/Cargo.toml
index 79b8dc3f2..6df491e98 100644
--- a/src/uu/expr/Cargo.toml
+++ b/src/uu/expr/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/expr.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 num-bigint = "0.4.0"
 num-traits = "0.2.14"
 onig = { version = "~6.3", default-features = false }
diff --git a/src/uu/expr/src/expr.rs b/src/uu/expr/src/expr.rs
index 188537fbc..f202b091c 100644
--- a/src/uu/expr/src/expr.rs
+++ b/src/uu/expr/src/expr.rs
@@ -5,7 +5,7 @@
 //* For the full copyright and license information, please view the LICENSE
 //* file that was distributed with this source code.
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::error::{UResult, USimpleError};
 use uucore::InvalidEncodingHandling;
 
@@ -19,12 +19,12 @@ static USAGE: &str = r#"
     expr [EXPRESSION]
     expr [OPTIONS]"#;
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(USAGE)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(VERSION)
                 .long(VERSION)
diff --git a/src/uu/expr/src/tokens.rs b/src/uu/expr/src/tokens.rs
index 247046941..a0365898d 100644
--- a/src/uu/expr/src/tokens.rs
+++ b/src/uu/expr/src/tokens.rs
@@ -65,7 +65,7 @@ impl Token {
         }
     }
     fn is_a_close_paren(&self) -> bool {
-        matches!(*self, Token::ParClose)
+        matches!(*self, Self::ParClose)
     }
 }
 
diff --git a/src/uu/factor/Cargo.toml b/src/uu/factor/Cargo.toml
index 2f688f98f..8c6587617 100644
--- a/src/uu/factor/Cargo.toml
+++ b/src/uu/factor/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 num-traits = "0.2.13" # used in src/numerics.rs, which is included by build.rs
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 coz = { version = "0.1.3", optional = true }
 num-traits = "0.2.13" # Needs at least version 0.2.13 for "OverflowingAdd"
 rand = { version = "0.8", features = ["small_rng"] }
diff --git a/src/uu/factor/src/cli.rs b/src/uu/factor/src/cli.rs
index 90f2fd3c8..f78e410ba 100644
--- a/src/uu/factor/src/cli.rs
+++ b/src/uu/factor/src/cli.rs
@@ -14,7 +14,7 @@ use std::fmt::Write as FmtWrite;
 use std::io::{self, stdin, stdout, BufRead, Write};
 
 mod factor;
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 pub use factor::*;
 use uucore::display::Quotable;
 use uucore::error::UResult;
@@ -77,10 +77,10 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(options::NUMBER).multiple_occurrences(true))
 }
diff --git a/src/uu/false/Cargo.toml b/src/uu/false/Cargo.toml
index 7cbdcd41c..d12702620 100644
--- a/src/uu/false/Cargo.toml
+++ b/src/uu/false/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/false.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/false/src/false.rs b/src/uu/false/src/false.rs
index c6661dc35..687235f70 100644
--- a/src/uu/false/src/false.rs
+++ b/src/uu/false/src/false.rs
@@ -4,7 +4,7 @@
 //  *
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use std::io::Write;
 use uucore::error::{set_exit_code, UResult};
 
@@ -18,7 +18,7 @@ the program will also return `1`.
 
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
-    let mut app = uu_app();
+    let mut command = uu_app();
 
     // Mirror GNU options, always return `1`. In particular even the 'successful' cases of no-op,
     // and the interrupted display of help and version should return `1`. Also, we return Ok in all
@@ -26,11 +26,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     // and unwind through the standard library allocation handling machinery.
     set_exit_code(1);
 
-    if let Ok(matches) = app.try_get_matches_from_mut(args) {
+    if let Ok(matches) = command.try_get_matches_from_mut(args) {
         let error = if matches.index_of("help").is_some() {
-            app.print_long_help()
+            command.print_long_help()
         } else if matches.index_of("version").is_some() {
-            writeln!(std::io::stdout(), "{}", app.render_version())
+            writeln!(std::io::stdout(), "{}", command.render_version())
         } else {
             Ok(())
         };
@@ -45,12 +45,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(clap::crate_version!())
         .about(ABOUT)
         // We provide our own help and version options, to ensure maximum compatibility with GNU.
-        .setting(AppSettings::DisableHelpFlag | AppSettings::DisableVersionFlag)
+        .disable_help_flag(true)
+        .disable_version_flag(true)
         .arg(
             Arg::new("help")
                 .long("help")
diff --git a/src/uu/fmt/Cargo.toml b/src/uu/fmt/Cargo.toml
index 862e175e2..221dd7e6a 100644
--- a/src/uu/fmt/Cargo.toml
+++ b/src/uu/fmt/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/fmt.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 unicode-width = "0.1.5"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/fmt/src/fmt.rs b/src/uu/fmt/src/fmt.rs
index e53617dac..3cb851674 100644
--- a/src/uu/fmt/src/fmt.rs
+++ b/src/uu/fmt/src/fmt.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::cmp;
 use std::fs::File;
 use std::io::{stdin, stdout, Write};
@@ -218,12 +218,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_CROWN_MARGIN)
                 .short('c')
diff --git a/src/uu/fold/Cargo.toml b/src/uu/fold/Cargo.toml
index 40e3fceb0..a6ffee120 100644
--- a/src/uu/fold/Cargo.toml
+++ b/src/uu/fold/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/fold.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/fold/src/fold.rs b/src/uu/fold/src/fold.rs
index d217f0bea..d24d31be9 100644
--- a/src/uu/fold/src/fold.rs
+++ b/src/uu/fold/src/fold.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDOs) ncount routput
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{stdin, BufRead, BufReader, Read};
 use std::path::Path;
@@ -63,13 +63,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     fold(&files, bytes, spaces, width)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BYTES)
                 .long(options::BYTES)
diff --git a/src/uu/groups/Cargo.toml b/src/uu/groups/Cargo.toml
index d7b3bf01f..bca2cc458 100644
--- a/src/uu/groups/Cargo.toml
+++ b/src/uu/groups/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/groups.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "process"] }
 
 [[bin]]
diff --git a/src/uu/groups/src/groups.rs b/src/uu/groups/src/groups.rs
index d4015fb50..cd0d05b07 100644
--- a/src/uu/groups/src/groups.rs
+++ b/src/uu/groups/src/groups.rs
@@ -26,7 +26,7 @@ use uucore::{
     format_usage,
 };
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 
 mod options {
     pub const USERS: &str = "USERNAME";
@@ -50,9 +50,9 @@ impl UError for GroupsError {}
 impl Display for GroupsError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {
-            GroupsError::GetGroupsFailed => write!(f, "failed to fetch groups"),
-            GroupsError::GroupNotFound(gid) => write!(f, "cannot find name for group ID {}", gid),
-            GroupsError::UserNotFound(user) => write!(f, "{}: no such user", user.quote()),
+            Self::GetGroupsFailed => write!(f, "failed to fetch groups"),
+            Self::GroupNotFound(gid) => write!(f, "cannot find name for group ID {}", gid),
+            Self::UserNotFound(user) => write!(f, "{}: no such user", user.quote()),
         }
     }
 }
@@ -102,12 +102,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::USERS)
                 .multiple_occurrences(true)
diff --git a/src/uu/hashsum/Cargo.toml b/src/uu/hashsum/Cargo.toml
index 24f8e87d1..febdeb5ec 100644
--- a/src/uu/hashsum/Cargo.toml
+++ b/src/uu/hashsum/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/hashsum.rs"
 
 [dependencies]
 digest = "0.10.1"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 hex = "0.4.3"
 memchr = "2"
 md-5 = "0.10.1"
diff --git a/src/uu/hashsum/src/digest.rs b/src/uu/hashsum/src/digest.rs
index 60275701e..9220e04a0 100644
--- a/src/uu/hashsum/src/digest.rs
+++ b/src/uu/hashsum/src/digest.rs
@@ -274,7 +274,7 @@ mod tests {
         use crate::digest::DigestWriter;
 
         // Writing "\r" in one call to `write()`, and then "\n" in another.
-        let mut digest = Box::new(md5::Context::new()) as Box<dyn Digest>;
+        let mut digest = Box::new(md5::Md5::new()) as Box<dyn Digest>;
         let mut writer_crlf = DigestWriter::new(&mut digest, false);
         writer_crlf.write_all(&[b'\r']).unwrap();
         writer_crlf.write_all(&[b'\n']).unwrap();
@@ -282,7 +282,7 @@ mod tests {
         let result_crlf = digest.result_str();
 
         // We expect "\r\n" to be replaced with "\n" in text mode on Windows.
-        let mut digest = Box::new(md5::Context::new()) as Box<dyn Digest>;
+        let mut digest = Box::new(md5::Md5::new()) as Box<dyn Digest>;
         let mut writer_lf = DigestWriter::new(&mut digest, false);
         writer_lf.write_all(&[b'\n']).unwrap();
         writer_lf.finalize();
diff --git a/src/uu/hashsum/src/hashsum.rs b/src/uu/hashsum/src/hashsum.rs
index d92336702..722585033 100644
--- a/src/uu/hashsum/src/hashsum.rs
+++ b/src/uu/hashsum/src/hashsum.rs
@@ -20,7 +20,7 @@ mod digest;
 use self::digest::Digest;
 use self::digest::DigestWriter;
 
-use clap::{App, AppSettings, Arg, ArgMatches};
+use clap::{Arg, ArgMatches, Command};
 use hex::encode;
 use md5::Md5;
 use regex::Regex;
@@ -297,13 +297,13 @@ pub fn uumain(mut args: impl uucore::Args) -> UResult<()> {
     // Default binary in Windows, text mode otherwise
     let binary_flag_default = cfg!(windows);
 
-    let app = uu_app(&binary_name);
+    let command = uu_app(&binary_name);
 
     // FIXME: this should use try_get_matches_from() and crash!(), but at the moment that just
     //        causes "error: " to be printed twice (once from crash!() and once from clap).  With
     //        the current setup, the name of the utility is not printed, but I think this is at
     //        least somewhat better from a user's perspective.
-    let matches = app.get_matches_from(args);
+    let matches = command.get_matches_from(args);
 
     let (name, algo, bits) = detect_algo(&binary_name, &matches);
 
@@ -340,7 +340,7 @@ pub fn uumain(mut args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app_common<'a>() -> App<'a> {
+pub fn uu_app_common<'a>() -> Command<'a> {
     #[cfg(windows)]
     const BINARY_HELP: &str = "read in binary mode (default)";
     #[cfg(not(windows))]
@@ -349,10 +349,10 @@ pub fn uu_app_common<'a>() -> App<'a> {
     const TEXT_HELP: &str = "read in text mode";
     #[cfg(not(windows))]
     const TEXT_HELP: &str = "read in text mode (default)";
-    App::new(uucore::util_name())
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about("Compute and check message digests.")
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new("binary")
                 .short('b')
@@ -419,8 +419,8 @@ pub fn uu_app_common<'a>() -> App<'a> {
         )
 }
 
-pub fn uu_app_custom<'a>() -> App<'a> {
-    let mut app = uu_app_common();
+pub fn uu_app_custom<'a>() -> Command<'a> {
+    let mut command = uu_app_common();
     let algorithms = &[
         ("md5", "work with MD5"),
         ("sha1", "work with SHA1"),
@@ -446,14 +446,14 @@ pub fn uu_app_custom<'a>() -> App<'a> {
     ];
 
     for (name, desc) in algorithms {
-        app = app.arg(Arg::new(*name).long(name).help(*desc));
+        command = command.arg(Arg::new(*name).long(name).help(*desc));
     }
-    app
+    command
 }
 
 // hashsum is handled differently in build.rs, therefore this is not the same
 // as in other utilities.
-fn uu_app<'a>(binary_name: &str) -> App<'a> {
+fn uu_app<'a>(binary_name: &str) -> Command<'a> {
     if !is_custom_binary(binary_name) {
         uu_app_custom()
     } else {
@@ -473,8 +473,8 @@ impl UError for HashsumError {}
 impl std::fmt::Display for HashsumError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {
-            HashsumError::InvalidRegex => write!(f, "invalid regular expression"),
-            HashsumError::InvalidFormat => Ok(()),
+            Self::InvalidRegex => write!(f, "invalid regular expression"),
+            Self::InvalidFormat => Ok(()),
         }
     }
 }
diff --git a/src/uu/head/Cargo.toml b/src/uu/head/Cargo.toml
index 65ac7f7cb..1744a4980 100644
--- a/src/uu/head/Cargo.toml
+++ b/src/uu/head/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/head.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 memchr = "2"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["ringbuffer", "lines"] }
 
diff --git a/src/uu/head/src/head.rs b/src/uu/head/src/head.rs
index 3bde78ec7..14780aa3c 100644
--- a/src/uu/head/src/head.rs
+++ b/src/uu/head/src/head.rs
@@ -5,7 +5,7 @@
 
 // spell-checker:ignore (vars) zlines BUFWRITER seekable
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::convert::{TryFrom, TryInto};
 use std::ffi::OsString;
 use std::io::{self, BufWriter, ErrorKind, Read, Seek, SeekFrom, Write};
@@ -41,12 +41,12 @@ mod take;
 use take::take_all_but;
 use take::take_lines;
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BYTES_NAME)
                 .short('c')
diff --git a/src/uu/hostid/Cargo.toml b/src/uu/hostid/Cargo.toml
index f0013fb05..148804768 100644
--- a/src/uu/hostid/Cargo.toml
+++ b/src/uu/hostid/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/hostid.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/hostid/src/hostid.rs b/src/uu/hostid/src/hostid.rs
index a82bb5e69..b60446e9f 100644
--- a/src/uu/hostid/src/hostid.rs
+++ b/src/uu/hostid/src/hostid.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) gethostid
 
-use clap::{crate_version, App, AppSettings};
+use clap::{crate_version, Command};
 use libc::c_long;
 use uucore::{error::UResult, format_usage};
 
@@ -26,12 +26,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(SUMMARY)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
 }
 
 fn hostid() {
diff --git a/src/uu/hostname/Cargo.toml b/src/uu/hostname/Cargo.toml
index 541642a4e..5f4a79c82 100644
--- a/src/uu/hostname/Cargo.toml
+++ b/src/uu/hostname/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/hostname.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 hostname = { version = "0.3", features = ["set"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["wide"] }
 winapi = { version="0.3", features=["sysinfoapi", "winsock2"] }
diff --git a/src/uu/hostname/src/hostname.rs b/src/uu/hostname/src/hostname.rs
index b45b4b1d8..757caed02 100644
--- a/src/uu/hostname/src/hostname.rs
+++ b/src/uu/hostname/src/hostname.rs
@@ -11,7 +11,7 @@ use std::collections::hash_set::HashSet;
 use std::net::ToSocketAddrs;
 use std::str;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 
 use uucore::{
     error::{FromIo, UResult},
@@ -71,12 +71,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_DOMAIN)
                 .short('d')
diff --git a/src/uu/id/Cargo.toml b/src/uu/id/Cargo.toml
index a0ccefbd0..ef7375691 100644
--- a/src/uu/id/Cargo.toml
+++ b/src/uu/id/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/id.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "process"] }
 selinux = { version="0.2", optional = true }
 
diff --git a/src/uu/id/src/id.rs b/src/uu/id/src/id.rs
index b1da51173..3bb9ce8c9 100644
--- a/src/uu/id/src/id.rs
+++ b/src/uu/id/src/id.rs
@@ -39,7 +39,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::ffi::CStr;
 use uucore::display::Quotable;
 use uucore::entries::{self, Group, Locate, Passwd};
@@ -341,12 +341,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::OPT_AUDIT)
                 .short('A')
diff --git a/src/uu/install/Cargo.toml b/src/uu/install/Cargo.toml
index bd0daab17..b39a9427e 100644
--- a/src/uu/install/Cargo.toml
+++ b/src/uu/install/Cargo.toml
@@ -18,7 +18,7 @@ edition = "2018"
 path = "src/install.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 filetime = "0.2"
 file_diff = "1.0.0"
 libc = ">= 0.2"
diff --git a/src/uu/install/src/install.rs b/src/uu/install/src/install.rs
index 9b72627fa..28d1aa702 100644
--- a/src/uu/install/src/install.rs
+++ b/src/uu/install/src/install.rs
@@ -12,7 +12,7 @@ mod mode;
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use file_diff::diff;
 use filetime::{set_file_times, FileTime};
 use uucore::backup_control::{self, BackupMode};
@@ -30,7 +30,7 @@ use std::fs;
 use std::fs::File;
 use std::os::unix::fs::MetadataExt;
 use std::path::{Path, PathBuf};
-use std::process::Command;
+use std::process;
 
 const DEFAULT_MODE: u32 = 0o755;
 const DEFAULT_STRIP_PROGRAM: &str = "strip";
@@ -188,12 +188,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             backup_control::arguments::backup()
         )
@@ -585,7 +585,7 @@ fn copy(from: &Path, to: &Path, b: &Behavior) -> UResult<()> {
     }
 
     if b.strip && cfg!(not(windows)) {
-        match Command::new(&b.strip_program).arg(to).output() {
+        match process::Command::new(&b.strip_program).arg(to).output() {
             Ok(o) => {
                 if !o.status.success() {
                     return Err(InstallError::StripProgramFailed(
diff --git a/src/uu/join/Cargo.toml b/src/uu/join/Cargo.toml
index 706b246c2..025307e7a 100644
--- a/src/uu/join/Cargo.toml
+++ b/src/uu/join/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/join.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 memchr = "2"
 
diff --git a/src/uu/join/src/join.rs b/src/uu/join/src/join.rs
index e5abefba4..1d306415b 100644
--- a/src/uu/join/src/join.rs
+++ b/src/uu/join/src/join.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use memchr::{memchr3_iter, memchr_iter};
 use std::cmp::Ordering;
 use std::convert::From;
@@ -697,8 +697,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(NAME)
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(NAME)
         .version(crate_version!())
         .about(
             "For each pair of input lines with identical join fields, write a line to
@@ -706,7 +706,7 @@ standard output. The default join field is the first, delimited by blanks.
 
 When FILE1 or FILE2 (not both) is -, read standard input.",
         )
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new("a")
                 .short('a')
diff --git a/src/uu/kill/Cargo.toml b/src/uu/kill/Cargo.toml
index 46853a85d..fb45a346b 100644
--- a/src/uu/kill/Cargo.toml
+++ b/src/uu/kill/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/kill.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["signals"] }
 
 [[bin]]
diff --git a/src/uu/kill/src/kill.rs b/src/uu/kill/src/kill.rs
index 2d0490921..df868e418 100644
--- a/src/uu/kill/src/kill.rs
+++ b/src/uu/kill/src/kill.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use libc::{c_int, pid_t};
 use std::io::Error;
 use uucore::display::Quotable;
@@ -78,12 +78,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::LIST)
                 .short('l')
diff --git a/src/uu/link/Cargo.toml b/src/uu/link/Cargo.toml
index 19ef1accc..d1a5e619a 100644
--- a/src/uu/link/Cargo.toml
+++ b/src/uu/link/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/link.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/link/src/link.rs b/src/uu/link/src/link.rs
index 9d515ee8a..3c959af33 100644
--- a/src/uu/link/src/link.rs
+++ b/src/uu/link/src/link.rs
@@ -4,7 +4,7 @@
 //  *
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::hard_link;
 use std::path::Path;
 use uucore::display::Quotable;
@@ -33,12 +33,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         .map_err_context(|| format!("cannot create link {} to {}", new.quote(), old.quote()))
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FILES)
                 .hide(true)
diff --git a/src/uu/ln/Cargo.toml b/src/uu/ln/Cargo.toml
index 4fa05372e..a40b78ba8 100644
--- a/src/uu/ln/Cargo.toml
+++ b/src/uu/ln/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/ln.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
 [[bin]]
diff --git a/src/uu/ln/src/ln.rs b/src/uu/ln/src/ln.rs
index ec4868876..2fc478a23 100644
--- a/src/uu/ln/src/ln.rs
+++ b/src/uu/ln/src/ln.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::display::Quotable;
 use uucore::error::{UError, UResult};
 use uucore::format_usage;
@@ -173,12 +173,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     exec(&paths[..], &settings)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(backup_control::arguments::backup())
         .arg(backup_control::arguments::backup_no_args())
         // TODO: opts.arg(
diff --git a/src/uu/logname/Cargo.toml b/src/uu/logname/Cargo.toml
index 8e1241b3b..c3112cba5 100644
--- a/src/uu/logname/Cargo.toml
+++ b/src/uu/logname/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/logname.rs"
 
 [dependencies]
-libc = "0.2.42"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/logname/src/logname.rs b/src/uu/logname/src/logname.rs
index 64ad5e9bc..31246b5c7 100644
--- a/src/uu/logname/src/logname.rs
+++ b/src/uu/logname/src/logname.rs
@@ -12,7 +12,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings};
+use clap::{crate_version, Command};
 use std::ffi::CStr;
 use uucore::error::UResult;
 use uucore::InvalidEncodingHandling;
@@ -51,10 +51,10 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .override_usage(uucore::execution_phrase())
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
 }
diff --git a/src/uu/ls/Cargo.toml b/src/uu/ls/Cargo.toml
index 6ad91e8e7..20b289173 100644
--- a/src/uu/ls/Cargo.toml
+++ b/src/uu/ls/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/ls.rs"
 
 [dependencies]
 chrono = "0.4.19"
-clap = { version = "3.0", features = ["wrap_help", "cargo", "env"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo", "env"] }
 unicode-width = "0.1.8"
 number_prefix = "0.4"
 term_grid = "0.1.5"
diff --git a/src/uu/ls/src/ls.rs b/src/uu/ls/src/ls.rs
index 9353d1f6b..a3fdef344 100644
--- a/src/uu/ls/src/ls.rs
+++ b/src/uu/ls/src/ls.rs
@@ -15,7 +15,7 @@ extern crate lazy_static;
 
 mod quoting_style;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use glob::Pattern;
 use lscolors::LsColors;
 use number_prefix::NumberPrefix;
@@ -116,6 +116,7 @@ pub mod options {
         pub static DIR_ARGS: &str = "dereference-command-line-symlink-to-dir";
     }
 
+    pub static HELP: &str = "help";
     pub static QUOTING_STYLE: &str = "quoting-style";
     pub static HIDE_CONTROL_CHARS: &str = "hide-control-chars";
     pub static SHOW_CONTROL_CHARS: &str = "show-control-chars";
@@ -782,9 +783,9 @@ impl Config {
 
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
-    let app = uu_app();
+    let command = uu_app();
 
-    let matches = app.get_matches_from(args);
+    let matches = command.get_matches_from(args);
 
     let config = Config::from(&matches)?;
 
@@ -796,8 +797,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     list(locs, &config)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(
@@ -805,7 +806,12 @@ pub fn uu_app<'a>() -> App<'a> {
             the command line, expect that it will ignore files and directories \
             whose names start with '.'.",
         )
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information.")
+        )
         // Format arguments
         .arg(
             Arg::new(options::FORMAT)
@@ -1196,12 +1202,18 @@ pub fn uu_app<'a>() -> App<'a> {
             Arg::new(options::files::ALL)
                 .short('a')
                 .long(options::files::ALL)
+                // Overrides -A (as the order matters)
+                .overrides_with(options::files::ALMOST_ALL)
+                .multiple_occurrences(true)
                 .help("Do not ignore hidden files (files with names that start with '.')."),
         )
         .arg(
             Arg::new(options::files::ALMOST_ALL)
                 .short('A')
                 .long(options::files::ALMOST_ALL)
+                // Overrides -a (as the order matters)
+                .overrides_with(options::files::ALL)
+                .multiple_occurrences(true)
                 .help(
                     "In a directory, do not ignore all file names that start with '.', \
 only ignore '.' and '..'.",
diff --git a/src/uu/mkdir/Cargo.toml b/src/uu/mkdir/Cargo.toml
index 978801a8e..620c0b85f 100644
--- a/src/uu/mkdir/Cargo.toml
+++ b/src/uu/mkdir/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/mkdir.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs", "mode"] }
 
 [[bin]]
diff --git a/src/uu/mkdir/src/mkdir.rs b/src/uu/mkdir/src/mkdir.rs
index 14b1ebaf5..ed487bb58 100644
--- a/src/uu/mkdir/src/mkdir.rs
+++ b/src/uu/mkdir/src/mkdir.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches, OsValues};
+use clap::{crate_version, Arg, ArgMatches, Command, OsValues};
 use std::path::Path;
 use uucore::display::Quotable;
 #[cfg(not(windows))]
@@ -104,12 +104,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::MODE)
                 .short('m')
diff --git a/src/uu/mkfifo/Cargo.toml b/src/uu/mkfifo/Cargo.toml
index 473cc0143..5fe9c9eb5 100644
--- a/src/uu/mkfifo/Cargo.toml
+++ b/src/uu/mkfifo/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/mkfifo.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/mkfifo/src/mkfifo.rs b/src/uu/mkfifo/src/mkfifo.rs
index 2ac316f9d..756fd75cf 100644
--- a/src/uu/mkfifo/src/mkfifo.rs
+++ b/src/uu/mkfifo/src/mkfifo.rs
@@ -8,7 +8,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use libc::mkfifo;
 use std::ffi::CString;
 use uucore::error::{UResult, USimpleError};
@@ -70,13 +70,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::MODE)
                 .short('m')
diff --git a/src/uu/mknod/Cargo.toml b/src/uu/mknod/Cargo.toml
index 9bed05fd4..8a21d9a82 100644
--- a/src/uu/mknod/Cargo.toml
+++ b/src/uu/mknod/Cargo.toml
@@ -16,8 +16,8 @@ name = "uu_mknod"
 path = "src/mknod.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "^0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "^0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["mode"] }
 
 [[bin]]
diff --git a/src/uu/mknod/src/mknod.rs b/src/uu/mknod/src/mknod.rs
index a27a48056..0e7c4be45 100644
--- a/src/uu/mknod/src/mknod.rs
+++ b/src/uu/mknod/src/mknod.rs
@@ -9,7 +9,7 @@
 
 use std::ffi::CString;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use libc::{dev_t, mode_t};
 use libc::{S_IFBLK, S_IFCHR, S_IFIFO, S_IRGRP, S_IROTH, S_IRUSR, S_IWGRP, S_IWOTH, S_IWUSR};
 
@@ -143,13 +143,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .after_help(LONG_HELP)
         .about(ABOUT)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new("mode")
                 .short('m')
diff --git a/src/uu/mktemp/Cargo.toml b/src/uu/mktemp/Cargo.toml
index 1ae00fa6f..0fe2ea07d 100644
--- a/src/uu/mktemp/Cargo.toml
+++ b/src/uu/mktemp/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/mktemp.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 rand = "0.8"
 tempfile = "3"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
diff --git a/src/uu/mktemp/src/mktemp.rs b/src/uu/mktemp/src/mktemp.rs
index 54d3ac651..54283b9af 100644
--- a/src/uu/mktemp/src/mktemp.rs
+++ b/src/uu/mktemp/src/mktemp.rs
@@ -8,7 +8,7 @@
 
 // spell-checker:ignore (paths) GPGHome
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::display::{println_verbatim, Quotable};
 use uucore::error::{FromIo, UError, UResult};
 use uucore::format_usage;
@@ -131,12 +131,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_DIRECTORY)
                 .short('d')
diff --git a/src/uu/more/Cargo.toml b/src/uu/more/Cargo.toml
index 9ce4172aa..76f0ebaba 100644
--- a/src/uu/more/Cargo.toml
+++ b/src/uu/more/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/more.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version = ">=0.0.7", package = "uucore", path = "../../uucore" }
 crossterm = ">=0.19"
 atty = "0.2"
diff --git a/src/uu/more/src/more.rs b/src/uu/more/src/more.rs
index db6ad249b..ab94bd435 100644
--- a/src/uu/more/src/more.rs
+++ b/src/uu/more/src/more.rs
@@ -17,7 +17,7 @@ use std::{
 #[cfg(all(unix, not(target_os = "fuchsia")))]
 extern crate nix;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use crossterm::{
     event::{self, Event, KeyCode, KeyEvent, KeyModifiers},
     execute, queue,
@@ -96,11 +96,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .about("A file perusal filter for CRT viewing.")
         .version(crate_version!())
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::SILENT)
                 .short('d')
diff --git a/src/uu/mv/Cargo.toml b/src/uu/mv/Cargo.toml
index 79012b5e0..3d7ae0791 100644
--- a/src/uu/mv/Cargo.toml
+++ b/src/uu/mv/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/mv.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 fs_extra = "1.1.0"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/mv/src/mv.rs b/src/uu/mv/src/mv.rs
index c02f70dbd..60cff5dfb 100644
--- a/src/uu/mv/src/mv.rs
+++ b/src/uu/mv/src/mv.rs
@@ -13,7 +13,7 @@ mod error;
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::env;
 use std::ffi::OsString;
 use std::fs;
@@ -112,12 +112,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     exec(&files[..], &behavior)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
     .arg(
         backup_control::arguments::backup()
     )
diff --git a/src/uu/nice/Cargo.toml b/src/uu/nice/Cargo.toml
index fc42cb801..e139d9102 100644
--- a/src/uu/nice/Cargo.toml
+++ b/src/uu/nice/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/nice.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 nix = "0.23.1"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/nice/src/nice.rs b/src/uu/nice/src/nice.rs
index 94ccbe61e..b75dd979e 100644
--- a/src/uu/nice/src/nice.rs
+++ b/src/uu/nice/src/nice.rs
@@ -15,7 +15,7 @@ use std::ffi::CString;
 use std::io::Error;
 use std::ptr;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::{
     error::{set_exit_code, UResult, USimpleError, UUsageError},
     format_usage,
@@ -102,12 +102,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::TrailingVarArg)
-        .setting(AppSettings::InferLongArgs)
+        .trailing_var_arg(true)
+        .infer_long_args(true)
         .version(crate_version!())
         .arg(
             Arg::new(options::ADJUSTMENT)
diff --git a/src/uu/nl/Cargo.toml b/src/uu/nl/Cargo.toml
index 5753cde72..be304d953 100644
--- a/src/uu/nl/Cargo.toml
+++ b/src/uu/nl/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/nl.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 regex = "1.0.1"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/nl/src/nl.rs b/src/uu/nl/src/nl.rs
index c1661178f..28cf3fb4d 100644
--- a/src/uu/nl/src/nl.rs
+++ b/src/uu/nl/src/nl.rs
@@ -8,7 +8,7 @@
 
 // spell-checker:ignore (ToDO) corasick memchr
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{stdin, BufRead, BufReader, Read};
 use std::iter::repeat;
@@ -66,6 +66,7 @@ enum NumberFormat {
 }
 
 pub mod options {
+    pub const HELP: &str = "help";
     pub const FILE: &str = "file";
     pub const BODY_NUMBERING: &str = "body-numbering";
     pub const SECTION_DELIMITER: &str = "section-delimiter";
@@ -139,12 +140,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information."),
+        )
         .arg(
             Arg::new(options::FILE)
                 .hide(true)
diff --git a/src/uu/nohup/Cargo.toml b/src/uu/nohup/Cargo.toml
index a19de6eb5..78510ec96 100644
--- a/src/uu/nohup/Cargo.toml
+++ b/src/uu/nohup/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/nohup.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 atty = "0.2"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
diff --git a/src/uu/nohup/src/nohup.rs b/src/uu/nohup/src/nohup.rs
index c7c7350cc..cfafb6b5b 100644
--- a/src/uu/nohup/src/nohup.rs
+++ b/src/uu/nohup/src/nohup.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use libc::{c_char, dup2, execvp, signal};
 use libc::{SIGHUP, SIG_IGN};
 use std::env;
@@ -58,7 +58,7 @@ impl std::error::Error for NohupError {}
 impl UError for NohupError {
     fn code(&self) -> i32 {
         match self {
-            NohupError::OpenFailed(code, _) | NohupError::OpenFailed2(code, _, _, _) => *code,
+            Self::OpenFailed(code, _) | Self::OpenFailed2(code, _, _, _) => *code,
             _ => 2,
         }
     }
@@ -67,9 +67,9 @@ impl UError for NohupError {
 impl Display for NohupError {
     fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
         match self {
-            NohupError::CannotDetach => write!(f, "Cannot detach from console"),
-            NohupError::CannotReplace(s, e) => write!(f, "Cannot replace {}: {}", s, e),
-            NohupError::OpenFailed(_, e) => {
+            Self::CannotDetach => write!(f, "Cannot detach from console"),
+            Self::CannotReplace(s, e) => write!(f, "Cannot replace {}: {}", s, e),
+            Self::OpenFailed(_, e) => {
                 write!(f, "failed to open {}: {}", NOHUP_OUT.quote(), e)
             }
             NohupError::OpenFailed2(_, e1, s, e2) => write!(
@@ -116,8 +116,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(LONG_HELP)
@@ -128,8 +128,8 @@ pub fn uu_app<'a>() -> App<'a> {
                 .required(true)
                 .multiple_occurrences(true),
         )
-        .setting(AppSettings::TrailingVarArg)
-        .setting(AppSettings::InferLongArgs)
+        .trailing_var_arg(true)
+        .infer_long_args(true)
 }
 
 fn replace_fds() -> UResult<()> {
diff --git a/src/uu/nproc/Cargo.toml b/src/uu/nproc/Cargo.toml
index ef9ee5b2a..38ed295cf 100644
--- a/src/uu/nproc/Cargo.toml
+++ b/src/uu/nproc/Cargo.toml
@@ -15,9 +15,9 @@ edition = "2018"
 path = "src/nproc.rs"
 
 [dependencies]
-libc = "0.2.42"
+libc = "0.2.121"
 num_cpus = "1.10"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
 [[bin]]
diff --git a/src/uu/nproc/src/nproc.rs b/src/uu/nproc/src/nproc.rs
index f10b41e40..87fe9a4e7 100644
--- a/src/uu/nproc/src/nproc.rs
+++ b/src/uu/nproc/src/nproc.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) NPROCESSORS nprocs numstr threadstr sysconf
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::env;
 use uucore::display::Quotable;
 use uucore::error::{UResult, USimpleError};
@@ -25,7 +25,9 @@ pub const _SC_NPROCESSORS_CONF: libc::c_int = 1001;
 static OPT_ALL: &str = "all";
 static OPT_IGNORE: &str = "ignore";
 
-static ABOUT: &str = "Print the number of cores available to the current process.";
+static ABOUT: &str = r#"Print the number of cores available to the current process.
+If the OMP_NUM_THREADS or OMP_THREAD_LIMIT environment variables are set, then
+they will determine the minimum and maximum returned value respectively."#;
 const USAGE: &str = "{} [OPTIONS]...";
 
 #[uucore::main]
@@ -45,6 +47,19 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         None => 0,
     };
 
+    let limit = match env::var("OMP_THREAD_LIMIT") {
+        // Uses the OpenMP variable to limit the number of threads
+        // If the parsing fails, returns the max size (so, no impact)
+        // If OMP_THREAD_LIMIT=0, rejects the value
+        Ok(threadstr) => match threadstr.parse() {
+            Ok(0) | Err(_) => usize::MAX,
+            Ok(n) => n,
+        },
+        // the variable 'OMP_THREAD_LIMIT' doesn't exist
+        // fallback to the max
+        Err(_) => usize::MAX,
+    };
+
     let mut cores = if matches.is_present(OPT_ALL) {
         num_cpus_all()
     } else {
@@ -52,13 +67,26 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         match env::var("OMP_NUM_THREADS") {
             // Uses the OpenMP variable to force the number of threads
             // If the parsing fails, returns the number of CPU
-            Ok(threadstr) => threadstr.parse().unwrap_or_else(|_| num_cpus::get()),
-            // the variable 'OMP_NUM_THREADS' doesn't exit
+            Ok(threadstr) => {
+                // In some cases, OMP_NUM_THREADS can be "x,y,z"
+                // In this case, only take the first one (like GNU)
+                // If OMP_NUM_THREADS=0, rejects the value
+                let thread: Vec<&str> = threadstr.split_terminator(',').collect();
+                match &thread[..] {
+                    [] => num_cpus::get(),
+                    [s, ..] => match s.parse() {
+                        Ok(0) | Err(_) => num_cpus::get(),
+                        Ok(n) => n,
+                    },
+                }
+            }
+            // the variable 'OMP_NUM_THREADS' doesn't exist
             // fallback to the regular CPU detection
             Err(_) => num_cpus::get(),
         }
     };
 
+    cores = std::cmp::min(limit, cores);
     if cores <= ignore {
         cores = 1;
     } else {
@@ -68,12 +96,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_ALL)
                 .long(OPT_ALL)
diff --git a/src/uu/numfmt/Cargo.toml b/src/uu/numfmt/Cargo.toml
index 8afc04f11..a2160beca 100644
--- a/src/uu/numfmt/Cargo.toml
+++ b/src/uu/numfmt/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/numfmt.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/numfmt/src/numfmt.rs b/src/uu/numfmt/src/numfmt.rs
index 516d7a4df..1b3ab3950 100644
--- a/src/uu/numfmt/src/numfmt.rs
+++ b/src/uu/numfmt/src/numfmt.rs
@@ -11,7 +11,7 @@ use crate::errors::*;
 use crate::format::format_and_print;
 use crate::options::*;
 use crate::units::{Result, Unit};
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::io::{BufRead, Write};
 use uucore::display::Quotable;
 use uucore::error::UResult;
@@ -186,14 +186,14 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::AllowNegativeNumbers)
-        .setting(AppSettings::InferLongArgs)
+        .allow_negative_numbers(true)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::DELIMITER)
                 .short('d')
diff --git a/src/uu/numfmt/src/options.rs b/src/uu/numfmt/src/options.rs
index bd76b18b8..f61d4c704 100644
--- a/src/uu/numfmt/src/options.rs
+++ b/src/uu/numfmt/src/options.rs
@@ -42,23 +42,23 @@ pub enum RoundMethod {
 impl RoundMethod {
     pub fn round(&self, f: f64) -> f64 {
         match self {
-            RoundMethod::Up => f.ceil(),
-            RoundMethod::Down => f.floor(),
-            RoundMethod::FromZero => {
+            Self::Up => f.ceil(),
+            Self::Down => f.floor(),
+            Self::FromZero => {
                 if f < 0.0 {
                     f.floor()
                 } else {
                     f.ceil()
                 }
             }
-            RoundMethod::TowardsZero => {
+            Self::TowardsZero => {
                 if f < 0.0 {
                     f.ceil()
                 } else {
                     f.floor()
                 }
             }
-            RoundMethod::Nearest => f.round(),
+            Self::Nearest => f.round(),
         }
     }
 }
diff --git a/src/uu/od/Cargo.toml b/src/uu/od/Cargo.toml
index 8e0c184a2..5907ab786 100644
--- a/src/uu/od/Cargo.toml
+++ b/src/uu/od/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/od.rs"
 
 [dependencies]
 byteorder = "1.3.2"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 half = "1.6"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/od/src/od.rs b/src/uu/od/src/od.rs
index 3bbe3ab5d..81cfb94de 100644
--- a/src/uu/od/src/od.rs
+++ b/src/uu/od/src/od.rs
@@ -5,7 +5,7 @@
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
 
-// spell-checker:ignore (clap) DontDelimitTrailingValues
+// spell-checker:ignore (clap) dont
 // spell-checker:ignore (ToDO) formatteriteminfo inputdecoder inputoffset mockstream nrofbytes partialreader odfunc multifile exitcode
 
 #[macro_use]
@@ -43,7 +43,7 @@ use crate::parse_nrofbytes::parse_number_of_bytes;
 use crate::partialreader::*;
 use crate::peekreader::*;
 use crate::prn_char::format_ascii_dump;
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, AppSettings, Arg, ArgMatches, Command};
 use uucore::display::Quotable;
 use uucore::error::{UResult, USimpleError};
 use uucore::format_usage;
@@ -98,6 +98,7 @@ If an error occurred, a diagnostic message will be printed to stderr, and the
 exitcode will be non-zero."#;
 
 pub(crate) mod options {
+    pub const HELP: &str = "help";
     pub const ADDRESS_RADIX: &str = "address-radix";
     pub const SKIP_BYTES: &str = "skip-bytes";
     pub const READ_BYTES: &str = "read-bytes";
@@ -289,17 +290,20 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     odfunc(&mut input_offset, &mut input_decoder, &output_info)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
         .after_help(LONG_HELP)
-        .setting(
-            AppSettings::TrailingVarArg |
-            AppSettings::DontDelimitTrailingValues |
-            AppSettings::DeriveDisplayOrder |
-            AppSettings::InferLongArgs
+        .trailing_var_arg(true)
+        .dont_delimit_trailing_values(true)
+        .infer_long_args(true)
+        .setting(AppSettings::DeriveDisplayOrder)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information.")
         )
         .arg(
             Arg::new(options::ADDRESS_RADIX)
diff --git a/src/uu/paste/Cargo.toml b/src/uu/paste/Cargo.toml
index c37c7a939..a2e3049b2 100644
--- a/src/uu/paste/Cargo.toml
+++ b/src/uu/paste/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/paste.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/paste/src/paste.rs b/src/uu/paste/src/paste.rs
index dc93ae625..2826a19e3 100644
--- a/src/uu/paste/src/paste.rs
+++ b/src/uu/paste/src/paste.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) delim
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{stdin, stdout, BufRead, BufReader, Read, Write};
 use std::path::Path;
@@ -47,11 +47,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     paste(files, serial, delimiters)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::SERIAL)
                 .long(options::SERIAL)
diff --git a/src/uu/pathchk/Cargo.toml b/src/uu/pathchk/Cargo.toml
index 982a4ea89..a60aa38ca 100644
--- a/src/uu/pathchk/Cargo.toml
+++ b/src/uu/pathchk/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/pathchk.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/pathchk/src/pathchk.rs b/src/uu/pathchk/src/pathchk.rs
index 2d72d4a5a..6260590aa 100644
--- a/src/uu/pathchk/src/pathchk.rs
+++ b/src/uu/pathchk/src/pathchk.rs
@@ -8,7 +8,7 @@
 //  * that was distributed with this source code.
 
 // spell-checker:ignore (ToDO) lstat
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs;
 use std::io::{ErrorKind, Write};
 use uucore::display::Quotable;
@@ -84,12 +84,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::POSIX)
                 .short('p')
diff --git a/src/uu/pinky/Cargo.toml b/src/uu/pinky/Cargo.toml
index 3bbffe981..57eabb874 100644
--- a/src/uu/pinky/Cargo.toml
+++ b/src/uu/pinky/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/pinky.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["utmpx", "entries"] }
 
 [[bin]]
diff --git a/src/uu/pinky/src/pinky.rs b/src/uu/pinky/src/pinky.rs
index 02ad09d20..437c20cf5 100644
--- a/src/uu/pinky/src/pinky.rs
+++ b/src/uu/pinky/src/pinky.rs
@@ -18,7 +18,7 @@ use std::io::BufReader;
 use std::fs::File;
 use std::os::unix::fs::MetadataExt;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::path::PathBuf;
 use uucore::{format_usage, InvalidEncodingHandling};
 
@@ -36,6 +36,7 @@ mod options {
     pub const OMIT_NAME_HOST: &str = "omit_name_host";
     pub const OMIT_NAME_HOST_TIME: &str = "omit_name_host_time";
     pub const USER: &str = "user";
+    pub const HELP: &str = "help";
 }
 
 fn get_long_usage() -> String {
@@ -123,12 +124,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::LONG_FORMAT)
                 .short('l')
@@ -180,6 +181,13 @@ pub fn uu_app<'a>() -> App<'a> {
                 .takes_value(true)
                 .multiple_occurrences(true),
         )
+        .arg(
+            // Redefine the help argument to not include the short flag
+            // since that conflicts with omit_project_file.
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information"),
+        )
 }
 
 struct Pinky {
diff --git a/src/uu/pr/Cargo.toml b/src/uu/pr/Cargo.toml
index 100f37998..e5e6ddcb8 100644
--- a/src/uu/pr/Cargo.toml
+++ b/src/uu/pr/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/pr.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.7", package="uucore", path="../../uucore", features=["entries"] }
 chrono = "0.4.19"
 quick-error = "2.0.1"
diff --git a/src/uu/pr/src/pr.rs b/src/uu/pr/src/pr.rs
index 79baf72c9..e18d29730 100644
--- a/src/uu/pr/src/pr.rs
+++ b/src/uu/pr/src/pr.rs
@@ -11,7 +11,7 @@ extern crate quick_error;
 
 use chrono::offset::Local;
 use chrono::DateTime;
-use clap::{App, AppSettings, Arg, ArgMatches};
+use clap::{AppSettings, Arg, ArgMatches, Command};
 use itertools::Itertools;
 use quick_error::ResultExt;
 use regex::Regex;
@@ -192,13 +192,13 @@ quick_error! {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(VERSION)
         .about(ABOUT)
         .after_help(AFTER_HELP)
-        .setting(AppSettings::InferLongArgs)
-        .setting(AppSettings::AllArgsOverrideSelf)
+        .infer_long_args(true)
+        .args_override_self(true)
         .setting(AppSettings::NoAutoHelp)
         .setting(AppSettings::NoAutoVersion)
         .arg(
@@ -383,8 +383,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
 
     let opt_args = recreate_arguments(&args);
 
-    let mut app = uu_app();
-    let matches = match app.try_get_matches_from_mut(opt_args) {
+    let mut command = uu_app();
+    let matches = match command.try_get_matches_from_mut(opt_args) {
         Ok(m) => m,
         Err(e) => {
             e.print()?;
@@ -394,12 +394,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     };
 
     if matches.is_present(options::VERSION) {
-        println!("{}", app.render_long_version());
+        println!("{}", command.render_long_version());
         return Ok(());
     }
 
     if matches.is_present(options::HELP) {
-        app.print_long_help()?;
+        command.print_long_help()?;
         return Ok(());
     }
 
diff --git a/src/uu/printenv/Cargo.toml b/src/uu/printenv/Cargo.toml
index ff8e6ffe1..bb684a1c4 100644
--- a/src/uu/printenv/Cargo.toml
+++ b/src/uu/printenv/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/printenv.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/printenv/src/printenv.rs b/src/uu/printenv/src/printenv.rs
index cb24299cc..c5832c4df 100644
--- a/src/uu/printenv/src/printenv.rs
+++ b/src/uu/printenv/src/printenv.rs
@@ -7,7 +7,7 @@
 
 /* last synced with: printenv (GNU coreutils) 8.13 */
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::env;
 use uucore::{error::UResult, format_usage};
 
@@ -56,12 +56,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_NULL)
                 .short('0')
diff --git a/src/uu/printf/Cargo.toml b/src/uu/printf/Cargo.toml
index 8a59d434f..ac539cb82 100644
--- a/src/uu/printf/Cargo.toml
+++ b/src/uu/printf/Cargo.toml
@@ -18,7 +18,7 @@ edition = "2018"
 path = "src/printf.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version = ">=0.0.11", package = "uucore", path = "../../uucore", features = ["memo"] }
 
 [[bin]]
diff --git a/src/uu/printf/src/printf.rs b/src/uu/printf/src/printf.rs
index 2dbc7f996..662db1ed5 100644
--- a/src/uu/printf/src/printf.rs
+++ b/src/uu/printf/src/printf.rs
@@ -2,7 +2,7 @@
 // spell-checker:ignore (change!) each's
 // spell-checker:ignore (ToDO) LONGHELP FORMATSTRING templating parameterizing formatstr
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::error::{UResult, UUsageError};
 use uucore::InvalidEncodingHandling;
 use uucore::{format_usage, memo};
@@ -288,9 +288,9 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
-        .setting(AppSettings::AllowHyphenValues)
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
+        .allow_hyphen_values(true)
         .version(crate_version!())
         .about(ABOUT)
         .after_help(AFTER_HELP)
diff --git a/src/uu/ptx/Cargo.toml b/src/uu/ptx/Cargo.toml
index 36f72aa85..f79ded44f 100644
--- a/src/uu/ptx/Cargo.toml
+++ b/src/uu/ptx/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/ptx.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 regex = "1.0.1"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/ptx/src/ptx.rs b/src/uu/ptx/src/ptx.rs
index 20a2b13f2..86a123530 100644
--- a/src/uu/ptx/src/ptx.rs
+++ b/src/uu/ptx/src/ptx.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDOs) corasick memchr Roff trunc oset iset
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use regex::Regex;
 use std::cmp;
 use std::collections::{BTreeSet, HashMap, HashSet};
@@ -174,11 +174,11 @@ impl UError for PtxError {}
 impl Display for PtxError {
     fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
         match self {
-            PtxError::DumbFormat => {
+            Self::DumbFormat => {
                 write!(f, "There is no dumb format with GNU extensions disabled")
             }
-            PtxError::NotImplemented(s) => write!(f, "{} not implemented yet", s),
-            PtxError::ParseError(e) => e.fmt(f),
+            Self::NotImplemented(s) => write!(f, "{} not implemented yet", s),
+            Self::ParseError(e) => e.fmt(f),
         }
     }
 }
@@ -702,13 +702,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     write_traditional_output(&config, &file_map, &word_set, &output_file)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .about(ABOUT)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FILE)
                 .hide(true)
diff --git a/src/uu/pwd/Cargo.toml b/src/uu/pwd/Cargo.toml
index faf718ebd..d6c5567e2 100644
--- a/src/uu/pwd/Cargo.toml
+++ b/src/uu/pwd/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/pwd.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/pwd/src/pwd.rs b/src/uu/pwd/src/pwd.rs
index 28487545c..67462ac16 100644
--- a/src/uu/pwd/src/pwd.rs
+++ b/src/uu/pwd/src/pwd.rs
@@ -5,7 +5,7 @@
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::env;
 use std::io;
 use std::path::PathBuf;
@@ -148,12 +148,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_LOGICAL)
                 .short('L')
diff --git a/src/uu/readlink/Cargo.toml b/src/uu/readlink/Cargo.toml
index 3f8de61e9..19a92d48b 100644
--- a/src/uu/readlink/Cargo.toml
+++ b/src/uu/readlink/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/readlink.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
 [[bin]]
diff --git a/src/uu/readlink/src/readlink.rs b/src/uu/readlink/src/readlink.rs
index adbae7a27..ba1e368f2 100644
--- a/src/uu/readlink/src/readlink.rs
+++ b/src/uu/readlink/src/readlink.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs;
 use std::io::{stdout, Write};
 use std::path::{Path, PathBuf};
@@ -95,12 +95,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_help(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_CANONICALIZE)
                 .short('f')
diff --git a/src/uu/realpath/Cargo.toml b/src/uu/realpath/Cargo.toml
index cabd33256..706b73c1b 100644
--- a/src/uu/realpath/Cargo.toml
+++ b/src/uu/realpath/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/realpath.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
 [[bin]]
diff --git a/src/uu/realpath/src/realpath.rs b/src/uu/realpath/src/realpath.rs
index 4a42930f3..bea89c19e 100644
--- a/src/uu/realpath/src/realpath.rs
+++ b/src/uu/realpath/src/realpath.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::{
     io::{stdout, Write},
     path::{Path, PathBuf},
@@ -70,12 +70,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_QUIET)
                 .short('q')
diff --git a/src/uu/relpath/Cargo.toml b/src/uu/relpath/Cargo.toml
index 29eab9ac2..3c31e7f3e 100644
--- a/src/uu/relpath/Cargo.toml
+++ b/src/uu/relpath/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/relpath.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
 [[bin]]
diff --git a/src/uu/relpath/src/relpath.rs b/src/uu/relpath/src/relpath.rs
index a7da7a956..2e45ce927 100644
--- a/src/uu/relpath/src/relpath.rs
+++ b/src/uu/relpath/src/relpath.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) subpath absto absfrom absbase
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::env;
 use std::path::{Path, PathBuf};
 use uucore::display::println_verbatim;
@@ -78,12 +78,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     println_verbatim(result).map_err_context(String::new)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(options::DIR).short('d').takes_value(true).help(
             "If any of FROM and TO is not subpath of DIR, output absolute path instead of relative",
         ))
diff --git a/src/uu/rm/Cargo.toml b/src/uu/rm/Cargo.toml
index 2ef29d435..1e1b2464e 100644
--- a/src/uu/rm/Cargo.toml
+++ b/src/uu/rm/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/rm.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 walkdir = "2.2"
 remove_dir_all = "0.5.1"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
diff --git a/src/uu/rm/src/rm.rs b/src/uu/rm/src/rm.rs
index 9179c6d9f..a1924b41d 100644
--- a/src/uu/rm/src/rm.rs
+++ b/src/uu/rm/src/rm.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use remove_dir_all::remove_dir_all;
 use std::collections::VecDeque;
 use std::fs;
@@ -139,12 +139,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_FORCE)
             .short('f')
diff --git a/src/uu/rmdir/Cargo.toml b/src/uu/rmdir/Cargo.toml
index 86d5031c8..97ce48b1e 100644
--- a/src/uu/rmdir/Cargo.toml
+++ b/src/uu/rmdir/Cargo.toml
@@ -15,9 +15,9 @@ edition = "2018"
 path = "src/rmdir.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
-libc = "0.2.42"
+libc = "0.2.121"
 
 [[bin]]
 name = "rmdir"
diff --git a/src/uu/rmdir/src/rmdir.rs b/src/uu/rmdir/src/rmdir.rs
index bdb6ab60d..127b8fcf9 100644
--- a/src/uu/rmdir/src/rmdir.rs
+++ b/src/uu/rmdir/src/rmdir.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::{read_dir, remove_dir};
 use std::io;
 use std::path::Path;
@@ -170,12 +170,12 @@ struct Opts {
     verbose: bool,
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_IGNORE_FAIL_NON_EMPTY)
                 .long(OPT_IGNORE_FAIL_NON_EMPTY)
diff --git a/src/uu/runcon/Cargo.toml b/src/uu/runcon/Cargo.toml
index 3df1c70dc..4e3e2befa 100644
--- a/src/uu/runcon/Cargo.toml
+++ b/src/uu/runcon/Cargo.toml
@@ -14,7 +14,7 @@ edition = "2018"
 path = "src/runcon.rs"
 
 [dependencies]
-clap         = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap         = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore       = { version = ">=0.0.9", package="uucore", path="../../uucore", features=["entries", "fs", "perms"] }
 selinux      = { version = "0.2"   }
 thiserror    = { version = "1.0"   }
diff --git a/src/uu/runcon/src/runcon.rs b/src/uu/runcon/src/runcon.rs
index 55186d218..8c20319be 100644
--- a/src/uu/runcon/src/runcon.rs
+++ b/src/uu/runcon/src/runcon.rs
@@ -2,7 +2,7 @@
 
 use uucore::error::{UResult, UUsageError};
 
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use selinux::{OpaqueSecurityContext, SecurityClass, SecurityContext};
 use uucore::format_usage;
 
@@ -48,7 +48,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         Ok(r) => r,
         Err(r) => {
             if let Error::CommandLine(ref r) = r {
-                match r.kind {
+                match r.kind() {
                     clap::ErrorKind::DisplayHelp | clap::ErrorKind::DisplayVersion => {
                         println!("{}", r);
                         return Ok(());
@@ -103,13 +103,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(VERSION)
         .about(ABOUT)
         .after_help(DESCRIPTION)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::COMPUTE)
                 .short('c')
@@ -162,7 +162,7 @@ pub fn uu_app<'a>() -> App<'a> {
         //
         // This is not how POSIX does things, but this is how the GNU implementation
         // parses its command line.
-        .setting(clap::AppSettings::TrailingVarArg)
+        .trailing_var_arg(true)
 }
 
 #[derive(Debug)]
@@ -205,7 +205,7 @@ struct Options {
     arguments: Vec<OsString>,
 }
 
-fn parse_command_line(config: App, args: impl uucore::Args) -> Result<Options> {
+fn parse_command_line(config: Command, args: impl uucore::Args) -> Result<Options> {
     let matches = config.try_get_matches_from(args)?;
 
     let compute_transition_context = matches.is_present(options::COMPUTE);
diff --git a/src/uu/seq/Cargo.toml b/src/uu/seq/Cargo.toml
index fe986529d..ef405d531 100644
--- a/src/uu/seq/Cargo.toml
+++ b/src/uu/seq/Cargo.toml
@@ -17,7 +17,7 @@ path = "src/seq.rs"
 
 [dependencies]
 bigdecimal = "0.3"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 num-bigint = "0.4.0"
 num-traits = "0.2.14"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["memo"] }
diff --git a/src/uu/seq/src/extendedbigdecimal.rs b/src/uu/seq/src/extendedbigdecimal.rs
index 77d7fa423..253fadfd5 100644
--- a/src/uu/seq/src/extendedbigdecimal.rs
+++ b/src/uu/seq/src/extendedbigdecimal.rs
@@ -92,7 +92,7 @@ impl ExtendedBigDecimal {
     /// The smallest integer greater than or equal to this number.
     pub fn ceil(self) -> ExtendedBigInt {
         match self {
-            ExtendedBigDecimal::BigDecimal(x) => ExtendedBigInt::BigInt(ceil(x)),
+            Self::BigDecimal(x) => ExtendedBigInt::BigInt(ceil(x)),
             other => From::from(other),
         }
     }
@@ -100,7 +100,7 @@ impl ExtendedBigDecimal {
     /// The largest integer less than or equal to this number.
     pub fn floor(self) -> ExtendedBigInt {
         match self {
-            ExtendedBigDecimal::BigDecimal(x) => ExtendedBigInt::BigInt(floor(x)),
+            Self::BigDecimal(x) => ExtendedBigInt::BigInt(floor(x)),
             other => From::from(other),
         }
     }
@@ -121,17 +121,17 @@ impl From<ExtendedBigInt> for ExtendedBigDecimal {
 impl Display for ExtendedBigDecimal {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            ExtendedBigDecimal::BigDecimal(x) => {
+            Self::BigDecimal(x) => {
                 let (n, p) = x.as_bigint_and_exponent();
                 match p {
                     0 => Self::BigDecimal(BigDecimal::new(n * 10, 1)).fmt(f),
                     _ => x.fmt(f),
                 }
             }
-            ExtendedBigDecimal::Infinity => f32::INFINITY.fmt(f),
-            ExtendedBigDecimal::MinusInfinity => f32::NEG_INFINITY.fmt(f),
-            ExtendedBigDecimal::MinusZero => (-0.0f32).fmt(f),
-            ExtendedBigDecimal::Nan => "nan".fmt(f),
+            Self::Infinity => f32::INFINITY.fmt(f),
+            Self::MinusInfinity => f32::NEG_INFINITY.fmt(f),
+            Self::MinusZero => (-0.0f32).fmt(f),
+            Self::Nan => "nan".fmt(f),
         }
     }
 }
diff --git a/src/uu/seq/src/seq.rs b/src/uu/seq/src/seq.rs
index 788583a72..851857ea1 100644
--- a/src/uu/seq/src/seq.rs
+++ b/src/uu/seq/src/seq.rs
@@ -7,7 +7,7 @@
 use std::io::{stdout, ErrorKind, Write};
 use std::process::exit;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use num_traits::Zero;
 
 use uucore::error::FromIo;
@@ -141,11 +141,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
-        .setting(AppSettings::TrailingVarArg)
-        .setting(AppSettings::AllowNegativeNumbers)
-        .setting(AppSettings::InferLongArgs)
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
+        .trailing_var_arg(true)
+        .allow_negative_numbers(true)
+        .infer_long_args(true)
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
diff --git a/src/uu/shred/Cargo.toml b/src/uu/shred/Cargo.toml
index c89289f10..15914075a 100644
--- a/src/uu/shred/Cargo.toml
+++ b/src/uu/shred/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/shred.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 rand = "0.8"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/shred/src/shred.rs b/src/uu/shred/src/shred.rs
index 5c545e8e7..05c8d1805 100644
--- a/src/uu/shred/src/shred.rs
+++ b/src/uu/shred/src/shred.rs
@@ -8,7 +8,7 @@
 
 // spell-checker:ignore (words) writeback wipesync
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use rand::prelude::SliceRandom;
 use rand::Rng;
 use std::cell::{Cell, RefCell};
@@ -314,13 +314,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(AFTER_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FORCE)
                 .long(options::FORCE)
diff --git a/src/uu/shuf/Cargo.toml b/src/uu/shuf/Cargo.toml
index ab74e08b8..37c84da85 100644
--- a/src/uu/shuf/Cargo.toml
+++ b/src/uu/shuf/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/shuf.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 rand = "0.8"
 rand_core = "0.6"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
diff --git a/src/uu/shuf/src/shuf.rs b/src/uu/shuf/src/shuf.rs
index c331d7867..6a3e325c7 100644
--- a/src/uu/shuf/src/shuf.rs
+++ b/src/uu/shuf/src/shuf.rs
@@ -7,7 +7,7 @@
 
 // spell-checker:ignore (ToDO) cmdline evec seps rvec fdata
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use rand::prelude::SliceRandom;
 use rand::RngCore;
 use std::fs::File;
@@ -119,13 +119,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .about(ABOUT)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::ECHO)
                 .short('e')
@@ -134,7 +134,7 @@ pub fn uu_app<'a>() -> App<'a> {
                 .value_name("ARG")
                 .help("treat each ARG as an input line")
                 .multiple_occurrences(true)
-                .use_delimiter(false)
+                .use_value_delimiter(false)
                 .min_values(0)
                 .conflicts_with(options::INPUT_RANGE),
         )
diff --git a/src/uu/sleep/Cargo.toml b/src/uu/sleep/Cargo.toml
index 7f5413a3f..fc91d43b6 100644
--- a/src/uu/sleep/Cargo.toml
+++ b/src/uu/sleep/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/sleep.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/sleep/src/sleep.rs b/src/uu/sleep/src/sleep.rs
index 87cd15417..4d5095c31 100644
--- a/src/uu/sleep/src/sleep.rs
+++ b/src/uu/sleep/src/sleep.rs
@@ -9,11 +9,11 @@ use std::thread;
 use std::time::Duration;
 
 use uucore::{
-    error::{UResult, USimpleError},
+    error::{UResult, UUsageError},
     format_usage,
 };
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 
 static ABOUT: &str = "Pause for NUMBER seconds.";
 const USAGE: &str = "\
@@ -41,13 +41,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::NUMBER)
                 .help("pause for NUMBER seconds")
@@ -64,7 +64,7 @@ fn sleep(args: &[&str]) -> UResult<()> {
             Duration::new(0, 0),
             |result, arg| match uucore::parse_time::from_str(&arg[..]) {
                 Ok(m) => Ok(m.saturating_add(result)),
-                Err(f) => Err(USimpleError::new(1, f)),
+                Err(f) => Err(UUsageError::new(1, f)),
             },
         )?;
     thread::sleep(sleep_dur);
diff --git a/src/uu/sort/Cargo.toml b/src/uu/sort/Cargo.toml
index 12b171b74..b1c152acf 100644
--- a/src/uu/sort/Cargo.toml
+++ b/src/uu/sort/Cargo.toml
@@ -16,13 +16,13 @@ path = "src/sort.rs"
 
 [dependencies]
 binary-heap-plus = "0.4.1"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 compare = "0.1.0"
 ctrlc = { version = "3.0", features = ["termination"] }
 fnv = "1.0.7"
 itertools = "0.10.0"
 memchr = "2.4.0"
-ouroboros = "0.14.2"
+ouroboros = "0.15.0"
 rand = "0.8"
 rayon = "1.5"
 tempfile = "3"
diff --git a/src/uu/sort/src/sort.rs b/src/uu/sort/src/sort.rs
index 1c118b15a..a1aa92a2b 100644
--- a/src/uu/sort/src/sort.rs
+++ b/src/uu/sort/src/sort.rs
@@ -25,7 +25,7 @@ mod numeric_str_cmp;
 mod tmp_dir;
 
 use chunks::LineData;
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use custom_str_cmp::custom_str_cmp;
 use ext_sort::ext_sort;
 use fnv::FnvHasher;
@@ -55,7 +55,7 @@ use uucore::{format_usage, InvalidEncodingHandling};
 use crate::tmp_dir::TmpDirWrapper;
 
 const ABOUT: &str = "\
-    Display sorted concatenation of all FILE(s).\
+    Display sorted concatenation of all FILE(s). \
     With no FILE, or when FILE is -, read standard input.";
 const USAGE: &str = "{} [OPTION]... [FILE]...";
 
@@ -98,6 +98,7 @@ mod options {
         pub const DIAGNOSE_FIRST: &str = "diagnose-first";
     }
 
+    pub const HELP: &str = "help";
     pub const DICTIONARY_ORDER: &str = "dictionary-order";
     pub const MERGE: &str = "merge";
     pub const DEBUG: &str = "debug";
@@ -180,7 +181,7 @@ impl UError for SortError {
 impl Display for SortError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            SortError::Disorder {
+            Self::Disorder {
                 file,
                 line_number,
                 line,
@@ -198,7 +199,7 @@ impl Display for SortError {
                     Ok(())
                 }
             }
-            SortError::OpenFailed { path, error } => {
+            Self::OpenFailed { path, error } => {
                 write!(
                     f,
                     "open failed: {}: {}",
@@ -206,10 +207,10 @@ impl Display for SortError {
                     strip_errno(error)
                 )
             }
-            SortError::ParseKeyError { key, msg } => {
+            Self::ParseKeyError { key, msg } => {
                 write!(f, "failed to parse key {}: {}", key.quote(), msg)
             }
-            SortError::ReadFailed { path, error } => {
+            Self::ReadFailed { path, error } => {
                 write!(
                     f,
                     "cannot read: {}: {}",
@@ -217,17 +218,17 @@ impl Display for SortError {
                     strip_errno(error)
                 )
             }
-            SortError::OpenTmpFileFailed { error } => {
+            Self::OpenTmpFileFailed { error } => {
                 write!(f, "failed to open temporary file: {}", strip_errno(error))
             }
-            SortError::CompressProgExecutionFailed { code } => {
+            Self::CompressProgExecutionFailed { code } => {
                 write!(f, "couldn't execute compress program: errno {}", code)
             }
-            SortError::CompressProgTerminatedAbnormally { prog } => {
+            Self::CompressProgTerminatedAbnormally { prog } => {
                 write!(f, "{} terminated abnormally", prog.quote())
             }
-            SortError::TmpDirCreationFailed => write!(f, "could not create temporary directory"),
-            SortError::Uft8Error { error } => write!(f, "{}", error),
+            Self::TmpDirCreationFailed => write!(f, "could not create temporary directory"),
+            Self::Uft8Error { error } => write!(f, "{}", error),
         }
     }
 }
@@ -246,13 +247,13 @@ enum SortMode {
 impl SortMode {
     fn get_short_name(&self) -> Option<char> {
         match self {
-            SortMode::Numeric => Some('n'),
-            SortMode::HumanNumeric => Some('h'),
-            SortMode::GeneralNumeric => Some('g'),
-            SortMode::Month => Some('M'),
-            SortMode::Version => Some('V'),
-            SortMode::Random => Some('R'),
-            SortMode::Default => None,
+            Self::Numeric => Some('n'),
+            Self::HumanNumeric => Some('h'),
+            Self::GeneralNumeric => Some('g'),
+            Self::Month => Some('M'),
+            Self::Version => Some('V'),
+            Self::Random => Some('R'),
+            Self::Default => None,
         }
     }
 }
@@ -1268,12 +1269,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     exec(&mut files, &settings, output, &mut tmp_dir)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information."),
+        )
         .arg(
             Arg::new(options::modes::SORT)
                 .long(options::modes::SORT)
@@ -1357,7 +1363,7 @@ pub fn uu_app<'a>() -> App<'a> {
                 .long(options::check::CHECK_SILENT)
                 .conflicts_with(options::OUTPUT)
                 .help(
-                    "exit successfully if the given file is already sorted,\
+                    "exit successfully if the given file is already sorted, \
                 and exit with status 1 otherwise.",
                 ),
         )
diff --git a/src/uu/split/Cargo.toml b/src/uu/split/Cargo.toml
index 233563d1c..2f34311c1 100644
--- a/src/uu/split/Cargo.toml
+++ b/src/uu/split/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/split.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 memchr = "2"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/split/src/filenames.rs b/src/uu/split/src/filenames.rs
index 31742194d..6f68caeb4 100644
--- a/src/uu/split/src/filenames.rs
+++ b/src/uu/split/src/filenames.rs
@@ -46,9 +46,9 @@ impl SuffixType {
     /// The radix to use when representing the suffix string as digits.
     pub fn radix(&self) -> u8 {
         match self {
-            SuffixType::Alphabetic => 26,
-            SuffixType::Decimal => 10,
-            SuffixType::Hexadecimal => 16,
+            Self::Alphabetic => 26,
+            Self::Decimal => 10,
+            Self::Hexadecimal => 16,
         }
     }
 }
diff --git a/src/uu/split/src/split.rs b/src/uu/split/src/split.rs
index 73abc966b..b64b92898 100644
--- a/src/uu/split/src/split.rs
+++ b/src/uu/split/src/split.rs
@@ -13,7 +13,7 @@ mod platform;
 
 use crate::filenames::FilenameIterator;
 use crate::filenames::SuffixType;
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::convert::TryInto;
 use std::env;
 use std::fmt;
@@ -62,13 +62,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about("Create output files containing consecutive or interleaved sections of input")
         .after_help(AFTER_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         // strategy (mutually exclusive)
         .arg(
             Arg::new(OPT_BYTES)
@@ -858,6 +858,11 @@ impl<'a> Write for LineBytesChunkWriter<'a> {
         // Loop until we have written all bytes in the input buffer
         // (or an IO error occurs).
         loop {
+            // If the buffer is empty, then we are done writing.
+            if buf.is_empty() {
+                return Ok(total_bytes_written);
+            }
+
             // If we have filled the current chunk with bytes, then
             // start a new chunk and initialize its corresponding
             // writer.
@@ -875,18 +880,12 @@ impl<'a> Write for LineBytesChunkWriter<'a> {
 
             // Find the first newline character in the buffer.
             match memchr::memchr(b'\n', buf) {
-                // If there is no newline character and the buffer is
-                // empty, then we are done writing.
-                None if buf.is_empty() => {
-                    return Ok(total_bytes_written);
-                }
-
                 // If there is no newline character and the buffer is
                 // not empty, then write as many bytes as we can and
                 // then move on to the next chunk if necessary.
                 None => {
                     let end = self.num_bytes_remaining_in_current_chunk;
-                    let num_bytes_written = self.inner.write(&buf[..end])?;
+                    let num_bytes_written = self.inner.write(&buf[..end.min(buf.len())])?;
                     self.num_bytes_remaining_in_current_chunk -= num_bytes_written;
                     total_bytes_written += num_bytes_written;
                     buf = &buf[num_bytes_written..];
@@ -984,6 +983,13 @@ where
         (num_chunks, chunk_size)
     };
 
+    // If we would have written zero chunks of output, then terminate
+    // immediately. This happens on `split -e -n 3 /dev/null`, for
+    // example.
+    if num_chunks == 0 {
+        return Ok(());
+    }
+
     let num_chunks: usize = num_chunks
         .try_into()
         .map_err(|_| USimpleError::new(1, "Number of chunks too big"))?;
@@ -1007,8 +1013,9 @@ where
         writers.push(writer);
     }
 
-    // This block evaluates to an object of type `std::io::Result<()>`.
-    {
+    // Capture the result of the `std::io::copy()` calls to check for
+    // `BrokenPipe`.
+    let result: std::io::Result<()> = {
         // Write `chunk_size` bytes from the reader into each writer
         // except the last.
         //
@@ -1025,8 +1032,12 @@ where
         io::copy(&mut reader.by_ref().take(last_chunk_size), &mut writers[i])?;
 
         Ok(())
+    };
+    match result {
+        Ok(_) => Ok(()),
+        Err(e) if e.kind() == ErrorKind::BrokenPipe => Ok(()),
+        Err(e) => Err(uio_error!(e, "input/output error")),
     }
-    .map_err_context(|| "I/O error".to_string())
 }
 
 /// Split a file into a specific number of chunks by line.
@@ -1204,6 +1215,7 @@ fn split(settings: &Settings) -> UResult<()> {
                     // indicate that. A special error message needs to be
                     // printed in that case.
                     ErrorKind::Other => Err(USimpleError::new(1, "output file suffixes exhausted")),
+                    ErrorKind::BrokenPipe => Ok(()),
                     _ => Err(uio_error!(e, "input/output error")),
                 },
             }
@@ -1223,6 +1235,7 @@ fn split(settings: &Settings) -> UResult<()> {
                     // indicate that. A special error message needs to be
                     // printed in that case.
                     ErrorKind::Other => Err(USimpleError::new(1, "output file suffixes exhausted")),
+                    ErrorKind::BrokenPipe => Ok(()),
                     _ => Err(uio_error!(e, "input/output error")),
                 },
             }
@@ -1242,6 +1255,7 @@ fn split(settings: &Settings) -> UResult<()> {
                     // indicate that. A special error message needs to be
                     // printed in that case.
                     ErrorKind::Other => Err(USimpleError::new(1, "output file suffixes exhausted")),
+                    ErrorKind::BrokenPipe => Ok(()),
                     _ => Err(uio_error!(e, "input/output error")),
                 },
             }
diff --git a/src/uu/stat/Cargo.toml b/src/uu/stat/Cargo.toml
index ecf5aa5bd..20086bef5 100644
--- a/src/uu/stat/Cargo.toml
+++ b/src/uu/stat/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/stat.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries", "libc", "fs", "fsext"] }
 
 [[bin]]
diff --git a/src/uu/stat/src/stat.rs b/src/uu/stat/src/stat.rs
index 3196c373d..cebc6c108 100644
--- a/src/uu/stat/src/stat.rs
+++ b/src/uu/stat/src/stat.rs
@@ -16,7 +16,7 @@ use uucore::fsext::{
 use uucore::libc::mode_t;
 use uucore::{entries, format_usage};
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::borrow::Cow;
 use std::convert::AsRef;
 use std::os::unix::fs::{FileTypeExt, MetadataExt};
@@ -980,12 +980,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::DEREFERENCE)
                 .short('L')
diff --git a/src/uu/stdbuf/Cargo.toml b/src/uu/stdbuf/Cargo.toml
index a977adfe6..939913c36 100644
--- a/src/uu/stdbuf/Cargo.toml
+++ b/src/uu/stdbuf/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/stdbuf.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 tempfile = "3"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/stdbuf/src/stdbuf.rs b/src/uu/stdbuf/src/stdbuf.rs
index 8bd28b626..2eedb038b 100644
--- a/src/uu/stdbuf/src/stdbuf.rs
+++ b/src/uu/stdbuf/src/stdbuf.rs
@@ -10,13 +10,13 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::convert::{TryFrom, TryInto};
 use std::fs::File;
 use std::io::{self, Write};
 use std::os::unix::process::ExitStatusExt;
 use std::path::PathBuf;
-use std::process::Command;
+use std::process;
 use tempfile::tempdir;
 use tempfile::TempDir;
 use uucore::error::{FromIo, UResult, USimpleError, UUsageError};
@@ -131,7 +131,7 @@ fn check_option(matches: &ArgMatches, name: &str) -> Result<BufferType, ProgramO
     }
 }
 
-fn set_command_env(command: &mut Command, buffer_name: &str, buffer_type: &BufferType) {
+fn set_command_env(command: &mut process::Command, buffer_name: &str, buffer_type: &BufferType) {
     match buffer_type {
         BufferType::Size(m) => {
             command.env(buffer_name, m.to_string());
@@ -164,7 +164,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let options = ProgramOptions::try_from(&matches).map_err(|e| UUsageError::new(125, e.0))?;
 
     let mut command_values = matches.values_of::<&str>(options::COMMAND).unwrap();
-    let mut command = Command::new(command_values.next().unwrap());
+    let mut command = process::Command::new(command_values.next().unwrap());
     let command_params: Vec<&str> = command_values.collect();
 
     let mut tmp_dir = tempdir().unwrap();
@@ -194,14 +194,14 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .after_help(LONG_HELP)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::TrailingVarArg)
-        .setting(AppSettings::InferLongArgs)
+        .trailing_var_arg(true)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::INPUT)
                 .long(options::INPUT)
diff --git a/src/uu/sum/Cargo.toml b/src/uu/sum/Cargo.toml
index 56a4edf9a..cca85e030 100644
--- a/src/uu/sum/Cargo.toml
+++ b/src/uu/sum/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/sum.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/sum/src/sum.rs b/src/uu/sum/src/sum.rs
index 4dacf61cb..501635910 100644
--- a/src/uu/sum/src/sum.rs
+++ b/src/uu/sum/src/sum.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{stdin, Read};
 use std::path::Path;
@@ -140,13 +140,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FILE)
                 .multiple_occurrences(true)
diff --git a/src/uu/sync/Cargo.toml b/src/uu/sync/Cargo.toml
index a84d8c192..edddee204 100644
--- a/src/uu/sync/Cargo.toml
+++ b/src/uu/sync/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/sync.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["wide"] }
 winapi = { version = "0.3", features = ["errhandlingapi", "fileapi", "handleapi", "std", "winbase", "winerror"] }
 
diff --git a/src/uu/sync/src/sync.rs b/src/uu/sync/src/sync.rs
index 773e49479..f9c18d500 100644
--- a/src/uu/sync/src/sync.rs
+++ b/src/uu/sync/src/sync.rs
@@ -9,7 +9,7 @@
 
 extern crate libc;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::path::Path;
 use uucore::display::Quotable;
 use uucore::error::{UResult, USimpleError};
@@ -190,12 +190,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::FILE_SYSTEM)
                 .short('f')
diff --git a/src/uu/tac/Cargo.toml b/src/uu/tac/Cargo.toml
index a430c1e53..89d1f6571 100644
--- a/src/uu/tac/Cargo.toml
+++ b/src/uu/tac/Cargo.toml
@@ -20,7 +20,7 @@ path = "src/tac.rs"
 memchr = "2"
 memmap2 = "0.5"
 regex = "1"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/tac/src/tac.rs b/src/uu/tac/src/tac.rs
index 925968f74..3151b97e2 100644
--- a/src/uu/tac/src/tac.rs
+++ b/src/uu/tac/src/tac.rs
@@ -8,7 +8,7 @@
 // spell-checker:ignore (ToDO) sbytes slen dlen memmem memmap Mmap mmap SIGBUS
 mod error;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use memchr::memmem;
 use memmap2::Mmap;
 use std::io::{stdin, stdout, BufWriter, Read, Write};
@@ -60,13 +60,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     tac(&files, before, regex, separator)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BEFORE)
                 .short('b')
diff --git a/src/uu/tail/Cargo.toml b/src/uu/tail/Cargo.toml
index 60272747c..39ce7b72b 100644
--- a/src/uu/tail/Cargo.toml
+++ b/src/uu/tail/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/tail.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["ringbuffer", "lines"] }
 
 [target.'cfg(windows)'.dependencies]
diff --git a/src/uu/tail/src/tail.rs b/src/uu/tail/src/tail.rs
index 27153117c..bbbc9810d 100644
--- a/src/uu/tail/src/tail.rs
+++ b/src/uu/tail/src/tail.rs
@@ -20,7 +20,7 @@ mod parse;
 mod platform;
 use chunks::ReverseChunks;
 
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use std::collections::VecDeque;
 use std::convert::TryInto;
 use std::ffi::OsString;
@@ -275,12 +275,12 @@ fn arg_iterate<'a>(
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BYTES)
                 .short('c')
diff --git a/src/uu/tee/Cargo.toml b/src/uu/tee/Cargo.toml
index b71e9b0ef..8dd41f7db 100644
--- a/src/uu/tee/Cargo.toml
+++ b/src/uu/tee/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/tee.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 retain_mut = "=0.1.2" # ToDO: [2021-01-01; rivy; maint/MinSRV] ~ v0.1.5 uses const generics which aren't stabilized until rust v1.51.0
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["libc"] }
 
diff --git a/src/uu/tee/src/tee.rs b/src/uu/tee/src/tee.rs
index a1ba6b201..d9c2e78f1 100644
--- a/src/uu/tee/src/tee.rs
+++ b/src/uu/tee/src/tee.rs
@@ -8,7 +8,7 @@
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use retain_mut::RetainMut;
 use std::fs::OpenOptions;
 use std::io::{copy, sink, stdin, stdout, Error, ErrorKind, Read, Result, Write};
@@ -55,13 +55,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
         .after_help("If a FILE is -, it refers to a file named - .")
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::APPEND)
                 .long(options::APPEND)
diff --git a/src/uu/test/Cargo.toml b/src/uu/test/Cargo.toml
index bf0558a7a..e45610547 100644
--- a/src/uu/test/Cargo.toml
+++ b/src/uu/test/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/test.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [target.'cfg(target_os = "redox")'.dependencies]
diff --git a/src/uu/test/src/test.rs b/src/uu/test/src/test.rs
index f91aaf8ea..e53ba4db1 100644
--- a/src/uu/test/src/test.rs
+++ b/src/uu/test/src/test.rs
@@ -10,7 +10,7 @@
 
 mod parser;
 
-use clap::{crate_version, App};
+use clap::{crate_version, Command};
 use parser::{parse, Operator, Symbol, UnaryOperator};
 use std::ffi::{OsStr, OsString};
 use uucore::display::Quotable;
@@ -90,8 +90,8 @@ for details about the options it supports.";
 
 const ABOUT: &str = "Check file types and compare values.";
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
@@ -108,7 +108,7 @@ pub fn uumain(mut args: impl uucore::Args) -> UResult<()> {
         // If invoked as [ we should recognize --help and --version (but not -h or -v)
         if args.len() == 1 && (args[0] == "--help" || args[0] == "--version") {
             // Let clap pretty-print help and version
-            App::new(binary_name)
+            Command::new(binary_name)
                 .version(crate_version!())
                 .about(ABOUT)
                 .override_usage(format_usage(USAGE))
diff --git a/src/uu/timeout/Cargo.toml b/src/uu/timeout/Cargo.toml
index c250381e8..a2bd8bb4e 100644
--- a/src/uu/timeout/Cargo.toml
+++ b/src/uu/timeout/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/timeout.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 nix = "0.23.1"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["process", "signals"] }
 
diff --git a/src/uu/timeout/src/timeout.rs b/src/uu/timeout/src/timeout.rs
index 3da0bcd2a..c48bee1e6 100644
--- a/src/uu/timeout/src/timeout.rs
+++ b/src/uu/timeout/src/timeout.rs
@@ -14,12 +14,12 @@ extern crate uucore;
 extern crate clap;
 
 use crate::status::ExitStatus;
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::io::ErrorKind;
-use std::process::{Child, Command, Stdio};
+use std::process::{self, Child, Stdio};
 use std::time::Duration;
 use uucore::display::Quotable;
-use uucore::error::{UResult, USimpleError};
+use uucore::error::{UResult, USimpleError, UUsageError};
 use uucore::process::ChildExt;
 use uucore::signals::{signal_by_name_or_value, signal_name_by_value};
 use uucore::{format_usage, InvalidEncodingHandling};
@@ -72,7 +72,7 @@ impl Config {
         let duration =
             match uucore::parse_time::from_str(options.value_of(options::DURATION).unwrap()) {
                 Ok(duration) => duration,
-                Err(err) => return Err(USimpleError::new(1, err)),
+                Err(err) => return Err(UUsageError::new(1, err)),
             };
 
         let preserve_status: bool = options.is_present(options::PRESERVE_STATUS);
@@ -103,9 +103,9 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         .collect_str(InvalidEncodingHandling::ConvertLossy)
         .accept_any();
 
-    let app = uu_app();
+    let command = uu_app();
 
-    let matches = app.get_matches_from(args);
+    let matches = command.get_matches_from(args);
 
     let config = Config::from(&matches)?;
     timeout(
@@ -119,8 +119,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     )
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new("timeout")
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new("timeout")
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
@@ -162,8 +162,8 @@ pub fn uu_app<'a>() -> App<'a> {
                 .required(true)
                 .multiple_occurrences(true)
         )
-        .setting(AppSettings::TrailingVarArg)
-        .setting(AppSettings::InferLongArgs)
+        .trailing_var_arg(true)
+        .infer_long_args(true)
 }
 
 /// Remove pre-existing SIGCHLD handlers that would make waiting for the child's exit code fail.
@@ -245,7 +245,7 @@ fn timeout(
     if !foreground {
         unsafe { libc::setpgid(0, 0) };
     }
-    let mut process = Command::new(&cmd[0])
+    let mut process = process::Command::new(&cmd[0])
         .args(&cmd[1..])
         .stdin(Stdio::inherit())
         .stdout(Stdio::inherit())
diff --git a/src/uu/touch/Cargo.toml b/src/uu/touch/Cargo.toml
index bb6e0dc1e..6a2d46f84 100644
--- a/src/uu/touch/Cargo.toml
+++ b/src/uu/touch/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/touch.rs"
 
 [dependencies]
 filetime = "0.2.1"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 time = "0.1.40"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["libc"] }
 
diff --git a/src/uu/touch/src/touch.rs b/src/uu/touch/src/touch.rs
index 2b56cdb95..864917574 100644
--- a/src/uu/touch/src/touch.rs
+++ b/src/uu/touch/src/touch.rs
@@ -13,7 +13,7 @@ pub extern crate filetime;
 #[macro_use]
 extern crate uucore;
 
-use clap::{crate_version, App, AppSettings, Arg, ArgGroup};
+use clap::{crate_version, Arg, ArgGroup, Command};
 use filetime::*;
 use std::fs::{self, File};
 use std::path::{Path, PathBuf};
@@ -31,6 +31,7 @@ pub mod options {
         pub static REFERENCE: &str = "reference";
         pub static CURRENT: &str = "current";
     }
+    pub static HELP: &str = "help";
     pub static ACCESS: &str = "access";
     pub static MODIFICATION: &str = "modification";
     pub static NO_CREATE: &str = "no-create";
@@ -149,12 +150,17 @@ Try 'touch --help' for more information."##,
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .arg(
+            Arg::new(options::HELP)
+                .long(options::HELP)
+                .help("Print help information."),
+        )
         .arg(
             Arg::new(options::ACCESS)
                 .short('a')
diff --git a/src/uu/tr/Cargo.toml b/src/uu/tr/Cargo.toml
index 4ecfe2045..efaa09fd1 100644
--- a/src/uu/tr/Cargo.toml
+++ b/src/uu/tr/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/tr.rs"
 
 [dependencies]
 nom = "7.1.0"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/tr/src/operation.rs b/src/uu/tr/src/operation.rs
index afb9a1881..2c88758c5 100644
--- a/src/uu/tr/src/operation.rs
+++ b/src/uu/tr/src/operation.rs
@@ -37,20 +37,20 @@ pub enum BadSequence {
 impl Display for BadSequence {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            BadSequence::MissingCharClassName => writeln!(f, "missing character class name '[::]'"),
-            BadSequence::MissingEquivalentClassChar => {
+            Self::MissingCharClassName => writeln!(f, "missing character class name '[::]'"),
+            Self::MissingEquivalentClassChar => {
                 writeln!(f, "missing equivalence class character '[==]'")
             }
-            BadSequence::MultipleCharRepeatInSet2 => {
+            Self::MultipleCharRepeatInSet2 => {
                 writeln!(f, "only one [c*] repeat construct may appear in string2")
             }
-            BadSequence::CharRepeatInSet1 => {
+            Self::CharRepeatInSet1 => {
                 writeln!(f, "the [c*] repeat construct may not appear in string1")
             }
-            BadSequence::InvalidRepeatCount(count) => {
+            Self::InvalidRepeatCount(count) => {
                 writeln!(f, "invalid repeat count '{}' in [c*n] construct", count)
             }
-            BadSequence::EmptySet2WhenNotTruncatingSet1 => {
+            Self::EmptySet2WhenNotTruncatingSet1 => {
                 writeln!(f, "when not truncating set1, string2 must be non-empty")
             }
         }
@@ -83,20 +83,20 @@ pub enum Sequence {
 impl Sequence {
     pub fn flatten(&self) -> Box<dyn Iterator<Item = char>> {
         match self {
-            Sequence::Char(c) => Box::new(std::iter::once(*c)),
-            Sequence::CharRange(l, r) => Box::new((*l..=*r).flat_map(std::char::from_u32)),
-            Sequence::CharStar(c) => Box::new(std::iter::repeat(*c)),
-            Sequence::CharRepeat(c, n) => Box::new(std::iter::repeat(*c).take(*n)),
-            Sequence::Alnum => Box::new(('0'..='9').chain('A'..='Z').chain('a'..='z')),
-            Sequence::Alpha => Box::new(('A'..='Z').chain('a'..='z')),
-            Sequence::Blank => Box::new(unicode_table::BLANK.iter().cloned()),
-            Sequence::Control => Box::new(
+            Self::Char(c) => Box::new(std::iter::once(*c)),
+            Self::CharRange(l, r) => Box::new((*l..=*r).flat_map(std::char::from_u32)),
+            Self::CharStar(c) => Box::new(std::iter::repeat(*c)),
+            Self::CharRepeat(c, n) => Box::new(std::iter::repeat(*c).take(*n)),
+            Self::Alnum => Box::new(('0'..='9').chain('A'..='Z').chain('a'..='z')),
+            Self::Alpha => Box::new(('A'..='Z').chain('a'..='z')),
+            Self::Blank => Box::new(unicode_table::BLANK.iter().cloned()),
+            Self::Control => Box::new(
                 (0..=31)
                     .chain(std::iter::once(127))
                     .flat_map(std::char::from_u32),
             ),
-            Sequence::Digit => Box::new('0'..='9'),
-            Sequence::Graph => Box::new(
+            Self::Digit => Box::new('0'..='9'),
+            Self::Graph => Box::new(
                 (48..=57) // digit
                     .chain(65..=90) // uppercase
                     .chain(97..=122) // lowercase
@@ -108,8 +108,8 @@ impl Sequence {
                     .chain(std::iter::once(32)) // space
                     .flat_map(std::char::from_u32),
             ),
-            Sequence::Lower => Box::new('a'..='z'),
-            Sequence::Print => Box::new(
+            Self::Lower => Box::new('a'..='z'),
+            Self::Print => Box::new(
                 (48..=57) // digit
                     .chain(65..=90) // uppercase
                     .chain(97..=122) // lowercase
@@ -120,16 +120,16 @@ impl Sequence {
                     .chain(123..=126)
                     .flat_map(std::char::from_u32),
             ),
-            Sequence::Punct => Box::new(
+            Self::Punct => Box::new(
                 (33..=47)
                     .chain(58..=64)
                     .chain(91..=96)
                     .chain(123..=126)
                     .flat_map(std::char::from_u32),
             ),
-            Sequence::Space => Box::new(unicode_table::SPACES.iter().cloned()),
-            Sequence::Upper => Box::new('A'..='Z'),
-            Sequence::Xdigit => Box::new(('0'..='9').chain('A'..='F').chain('a'..='f')),
+            Self::Space => Box::new(unicode_table::SPACES.iter().cloned()),
+            Self::Upper => Box::new('A'..='Z'),
+            Self::Xdigit => Box::new(('0'..='9').chain('A'..='F').chain('a'..='f')),
         }
     }
 
diff --git a/src/uu/tr/src/tr.rs b/src/uu/tr/src/tr.rs
index a92a7308a..dd8edc518 100644
--- a/src/uu/tr/src/tr.rs
+++ b/src/uu/tr/src/tr.rs
@@ -11,7 +11,7 @@ mod convert;
 mod operation;
 mod unicode_table;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use nom::AsBytes;
 use operation::{translate_input, Sequence, SqueezeOperation, TranslateOperation};
 use std::io::{stdin, stdout, BufReader, BufWriter};
@@ -137,13 +137,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::COMPLEMENT)
                 .visible_short_alias('C')
diff --git a/src/uu/true/Cargo.toml b/src/uu/true/Cargo.toml
index c737d2234..3dc1535e1 100644
--- a/src/uu/true/Cargo.toml
+++ b/src/uu/true/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/true.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/true/src/true.rs b/src/uu/true/src/true.rs
index 4a8452db6..57c3d2af5 100644
--- a/src/uu/true/src/true.rs
+++ b/src/uu/true/src/true.rs
@@ -4,7 +4,7 @@
 //  *
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use std::io::Write;
 use uucore::error::{set_exit_code, UResult};
 
@@ -18,13 +18,13 @@ operation causes the program to return `1` instead.
 
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
-    let mut app = uu_app();
+    let mut command = uu_app();
 
-    if let Ok(matches) = app.try_get_matches_from_mut(args) {
+    if let Ok(matches) = command.try_get_matches_from_mut(args) {
         let error = if matches.index_of("help").is_some() {
-            app.print_long_help()
+            command.print_long_help()
         } else if matches.index_of("version").is_some() {
-            writeln!(std::io::stdout(), "{}", app.render_version())
+            writeln!(std::io::stdout(), "{}", command.render_version())
         } else {
             Ok(())
         };
@@ -42,12 +42,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(clap::crate_version!())
         .about(ABOUT)
         // We provide our own help and version options, to ensure maximum compatibility with GNU.
-        .setting(AppSettings::DisableHelpFlag | AppSettings::DisableVersionFlag)
+        .disable_help_flag(true)
+        .disable_version_flag(true)
         .arg(
             Arg::new("help")
                 .long("help")
diff --git a/src/uu/truncate/Cargo.toml b/src/uu/truncate/Cargo.toml
index 3048df521..ce74d1367 100644
--- a/src/uu/truncate/Cargo.toml
+++ b/src/uu/truncate/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/truncate.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/truncate/src/truncate.rs b/src/uu/truncate/src/truncate.rs
index b88040fb8..6c9d8197b 100644
--- a/src/uu/truncate/src/truncate.rs
+++ b/src/uu/truncate/src/truncate.rs
@@ -6,7 +6,7 @@
 //  * file that was distributed with this source code.
 
 // spell-checker:ignore (ToDO) RFILE refsize rfilename fsize tsize
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::{metadata, OpenOptions};
 use std::io::ErrorKind;
 #[cfg(unix)]
@@ -115,7 +115,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         .try_get_matches_from(args)
         .map_err(|e| {
             e.print().expect("Error writing clap::Error");
-            match e.kind {
+            match e.kind() {
                 clap::ErrorKind::DisplayHelp | clap::ErrorKind::DisplayVersion => 0,
                 _ => 1,
             }
@@ -137,12 +137,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::IO_BLOCKS)
             .short('o')
diff --git a/src/uu/tsort/Cargo.toml b/src/uu/tsort/Cargo.toml
index 39e73f0a1..a107e8f27 100644
--- a/src/uu/tsort/Cargo.toml
+++ b/src/uu/tsort/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/tsort.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/tsort/src/tsort.rs b/src/uu/tsort/src/tsort.rs
index 61cb95256..aecd492fe 100644
--- a/src/uu/tsort/src/tsort.rs
+++ b/src/uu/tsort/src/tsort.rs
@@ -5,7 +5,7 @@
 //  *
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::collections::{HashMap, HashSet};
 use std::fs::File;
 use std::io::{stdin, BufRead, BufReader, Read};
@@ -93,12 +93,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(options::FILE).default_value("-").hide(true))
 }
 
diff --git a/src/uu/tty/Cargo.toml b/src/uu/tty/Cargo.toml
index 43a0d2edc..97cb2b357 100644
--- a/src/uu/tty/Cargo.toml
+++ b/src/uu/tty/Cargo.toml
@@ -15,8 +15,8 @@ edition = "2018"
 path = "src/tty.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
-libc = "0.2.42"
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
+libc = "0.2.121"
 atty = "0.2"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["fs"] }
 
diff --git a/src/uu/tty/src/tty.rs b/src/uu/tty/src/tty.rs
index e3d13b67d..b13b61784 100644
--- a/src/uu/tty/src/tty.rs
+++ b/src/uu/tty/src/tty.rs
@@ -9,7 +9,7 @@
 
 // spell-checker:ignore (ToDO) ttyname filedesc
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::ffi::CStr;
 use std::io::Write;
 use uucore::error::{UResult, UUsageError};
@@ -66,12 +66,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::SILENT)
                 .long(options::SILENT)
diff --git a/src/uu/uname/Cargo.toml b/src/uu/uname/Cargo.toml
index 4a68e1b64..7bfa19750 100644
--- a/src/uu/uname/Cargo.toml
+++ b/src/uu/uname/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/uname.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 platform-info = "0.2"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/uname/src/uname.rs b/src/uu/uname/src/uname.rs
index c5c2b8801..bff033047 100644
--- a/src/uu/uname/src/uname.rs
+++ b/src/uu/uname/src/uname.rs
@@ -10,7 +10,7 @@
 
 // spell-checker:ignore (ToDO) nodename kernelname kernelrelease kernelversion sysname hwplatform mnrsv
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use platform_info::*;
 use uucore::{
     error::{FromIo, UResult},
@@ -121,12 +121,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(options::ALL)
             .short('a')
             .long(options::ALL)
diff --git a/src/uu/unexpand/Cargo.toml b/src/uu/unexpand/Cargo.toml
index 86de08b9f..1df7061f3 100644
--- a/src/uu/unexpand/Cargo.toml
+++ b/src/uu/unexpand/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/unexpand.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 unicode-width = "0.1.5"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
diff --git a/src/uu/unexpand/src/unexpand.rs b/src/uu/unexpand/src/unexpand.rs
index 55bd51ad1..910ff91d3 100644
--- a/src/uu/unexpand/src/unexpand.rs
+++ b/src/uu/unexpand/src/unexpand.rs
@@ -11,7 +11,7 @@
 
 #[macro_use]
 extern crate uucore;
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::fs::File;
 use std::io::{stdin, stdout, BufRead, BufReader, BufWriter, Read, Stdout, Write};
 use std::str::from_utf8;
@@ -102,13 +102,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     unexpand(&Options::new(&matches)).map_err_context(String::new)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .name(NAME)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
         .about(SUMMARY)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(options::FILE).hide(true).multiple_occurrences(true))
         .arg(
             Arg::new(options::ALL)
diff --git a/src/uu/uniq/Cargo.toml b/src/uu/uniq/Cargo.toml
index 1fe571b0e..3f3840cbf 100644
--- a/src/uu/uniq/Cargo.toml
+++ b/src/uu/uniq/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/uniq.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 strum = "0.24.0"
 strum_macros = "0.23.1"
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
diff --git a/src/uu/uniq/src/uniq.rs b/src/uu/uniq/src/uniq.rs
index a22db42a9..020de0230 100644
--- a/src/uu/uniq/src/uniq.rs
+++ b/src/uu/uniq/src/uniq.rs
@@ -5,7 +5,7 @@
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 use std::fs::File;
 use std::io::{self, stdin, stdout, BufRead, BufReader, BufWriter, Read, Write};
 use std::path::Path;
@@ -290,12 +290,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     )
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::ALL_REPEATED)
                 .short('D')
diff --git a/src/uu/unlink/Cargo.toml b/src/uu/unlink/Cargo.toml
index 8d3ac6b26..323c74dba 100644
--- a/src/uu/unlink/Cargo.toml
+++ b/src/uu/unlink/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/unlink.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore" }
 
 [[bin]]
diff --git a/src/uu/unlink/src/unlink.rs b/src/uu/unlink/src/unlink.rs
index 65544612b..fc72b4623 100644
--- a/src/uu/unlink/src/unlink.rs
+++ b/src/uu/unlink/src/unlink.rs
@@ -10,7 +10,7 @@
 use std::fs::remove_file;
 use std::path::Path;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult};
@@ -27,11 +27,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     remove_file(path).map_err_context(|| format!("cannot unlink {}", path.quote()))
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(OPT_PATH)
                 .required(true)
diff --git a/src/uu/uptime/Cargo.toml b/src/uu/uptime/Cargo.toml
index 8edb568d3..471a1d950 100644
--- a/src/uu/uptime/Cargo.toml
+++ b/src/uu/uptime/Cargo.toml
@@ -16,7 +16,7 @@ path = "src/uptime.rs"
 
 [dependencies]
 chrono = "^0.4.11"
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["libc", "utmpx"] }
 
 [[bin]]
diff --git a/src/uu/uptime/src/uptime.rs b/src/uu/uptime/src/uptime.rs
index ac9ba6d15..a93344dbc 100644
--- a/src/uu/uptime/src/uptime.rs
+++ b/src/uu/uptime/src/uptime.rs
@@ -9,7 +9,7 @@
 // spell-checker:ignore (ToDO) getloadavg upsecs updays nusers loadavg boottime uphours upmins
 
 use chrono::{Local, TimeZone, Utc};
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 
 use uucore::format_usage;
 // import crate time from utmpx
@@ -59,12 +59,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::SINCE)
                 .short('s')
diff --git a/src/uu/users/Cargo.toml b/src/uu/users/Cargo.toml
index dfd6d0309..2b155ee03 100644
--- a/src/uu/users/Cargo.toml
+++ b/src/uu/users/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/users.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["utmpx"] }
 
 [[bin]]
diff --git a/src/uu/users/src/users.rs b/src/uu/users/src/users.rs
index 761080139..79fac3b68 100644
--- a/src/uu/users/src/users.rs
+++ b/src/uu/users/src/users.rs
@@ -10,7 +10,7 @@
 
 use std::path::Path;
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use uucore::error::UResult;
 use uucore::format_usage;
 use uucore::utmpx::{self, Utmpx};
@@ -58,11 +58,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(Arg::new(ARG_FILES).takes_value(true).max_values(1))
 }
diff --git a/src/uu/wc/Cargo.toml b/src/uu/wc/Cargo.toml
index 0e998b74e..d21e606dd 100644
--- a/src/uu/wc/Cargo.toml
+++ b/src/uu/wc/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/wc.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["pipes"] }
 bytecount = "0.6.2"
 utf-8 = "0.7.6"
diff --git a/src/uu/wc/src/wc.rs b/src/uu/wc/src/wc.rs
index a07877e0e..61eda6828 100644
--- a/src/uu/wc/src/wc.rs
+++ b/src/uu/wc/src/wc.rs
@@ -18,7 +18,7 @@ use utf8::{BufReadDecoder, BufReadDecoderError};
 use uucore::format_usage;
 use word_count::{TitledWordCount, WordCount};
 
-use clap::{crate_version, App, AppSettings, Arg, ArgMatches};
+use clap::{crate_version, Arg, ArgMatches, Command};
 
 use std::cmp::max;
 use std::error::Error;
@@ -183,12 +183,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     wc(&inputs, &settings)
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::BYTES)
                 .short('c')
diff --git a/src/uu/who/Cargo.toml b/src/uu/who/Cargo.toml
index c0fd70ae8..eac59709d 100644
--- a/src/uu/who/Cargo.toml
+++ b/src/uu/who/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/who.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["utmpx"] }
 
 [[bin]]
diff --git a/src/uu/who/src/who.rs b/src/uu/who/src/who.rs
index 8c0a66c36..98ef06f47 100644
--- a/src/uu/who/src/who.rs
+++ b/src/uu/who/src/who.rs
@@ -12,7 +12,7 @@ use uucore::error::{FromIo, UResult};
 use uucore::libc::{ttyname, STDIN_FILENO, S_IWGRP};
 use uucore::utmpx::{self, time, Utmpx};
 
-use clap::{crate_version, App, AppSettings, Arg};
+use clap::{crate_version, Arg, Command};
 use std::borrow::Cow;
 use std::ffi::CStr;
 use std::os::unix::fs::MetadataExt;
@@ -151,12 +151,12 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     who.exec()
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
         .override_usage(format_usage(USAGE))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
         .arg(
             Arg::new(options::ALL)
                 .long(options::ALL)
diff --git a/src/uu/whoami/Cargo.toml b/src/uu/whoami/Cargo.toml
index 151ef1141..807e99b35 100644
--- a/src/uu/whoami/Cargo.toml
+++ b/src/uu/whoami/Cargo.toml
@@ -15,14 +15,14 @@ edition = "2018"
 path = "src/whoami.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["entries"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = { version = "0.3", features = ["lmcons"] }
 
 [target.'cfg(unix)'.dependencies]
-libc = "0.2.42"
+libc = "0.2.121"
 
 [[bin]]
 name = "whoami"
diff --git a/src/uu/whoami/src/whoami.rs b/src/uu/whoami/src/whoami.rs
index f55e026da..770802764 100644
--- a/src/uu/whoami/src/whoami.rs
+++ b/src/uu/whoami/src/whoami.rs
@@ -10,7 +10,7 @@
 #[macro_use]
 extern crate clap;
 
-use clap::{App, AppSettings};
+use clap::Command;
 
 use uucore::display::println_verbatim;
 use uucore::error::{FromIo, UResult};
@@ -27,9 +27,9 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    App::new(uucore::util_name())
+pub fn uu_app<'a>() -> Command<'a> {
+    Command::new(uucore::util_name())
         .version(crate_version!())
         .about(ABOUT)
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
 }
diff --git a/src/uu/yes/Cargo.toml b/src/uu/yes/Cargo.toml
index 2054274f8..aad1af357 100644
--- a/src/uu/yes/Cargo.toml
+++ b/src/uu/yes/Cargo.toml
@@ -15,7 +15,7 @@ edition = "2018"
 path = "src/yes.rs"
 
 [dependencies]
-clap = { version = "3.0", features = ["wrap_help", "cargo"] }
+clap = { version = "3.1", features = ["wrap_help", "cargo"] }
 uucore = { version=">=0.0.11", package="uucore", path="../../uucore", features=["pipes"] }
 
 [target.'cfg(any(target_os = "linux", target_os = "android"))'.dependencies]
diff --git a/src/uu/yes/src/yes.rs b/src/uu/yes/src/yes.rs
index b237fb857..879f60579 100644
--- a/src/uu/yes/src/yes.rs
+++ b/src/uu/yes/src/yes.rs
@@ -13,7 +13,7 @@ use std::io::{self, Write};
 #[macro_use]
 extern crate clap;
 
-use clap::{App, AppSettings, Arg};
+use clap::{Arg, Command};
 use uucore::error::{UResult, USimpleError};
 use uucore::format_usage;
 
@@ -49,11 +49,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 }
 
-pub fn uu_app<'a>() -> App<'a> {
-    app_from_crate!()
+pub fn uu_app<'a>() -> Command<'a> {
+    command!()
         .override_usage(format_usage(USAGE))
         .arg(Arg::new("STRING").index(1).multiple_occurrences(true))
-        .setting(AppSettings::InferLongArgs)
+        .infer_long_args(true)
 }
 
 fn prepare_buffer<'a>(input: &'a str, buffer: &'a mut [u8; BUF_SIZE]) -> &'a [u8] {
diff --git a/src/uucore/Cargo.toml b/src/uucore/Cargo.toml
index 8aefa8380..d2d819edd 100644
--- a/src/uucore/Cargo.toml
+++ b/src/uucore/Cargo.toml
@@ -17,7 +17,7 @@ path="src/lib/lib.rs"
 
 [dependencies]
 uucore_procs = { version=">=0.0.12", path="../uucore_procs" }
-clap = "3.0"
+clap = "3.1"
 dns-lookup = { version="1.0.5", optional=true }
 dunce = "1.0.0"
 wild = "2.0"
@@ -29,7 +29,7 @@ time = { version="<= 0.1.43", optional=true }
 data-encoding = { version="2.1", optional=true }
 data-encoding-macro = { version="0.1.12", optional=true }
 z85 = { version="3.0.3", optional=true }
-libc = { version="0.2.15", optional=true }
+libc = { version="0.2.121", optional=true }
 once_cell = "1.10.0"
 os_display = "0.1.0"
 
@@ -38,7 +38,7 @@ walkdir = { version="2.3.2", optional=true }
 nix = { version="0.23.1", optional=true }
 
 [dev-dependencies]
-clap = "3.0"
+clap = "3.1"
 lazy_static = "1.3"
 
 [target.'cfg(target_os = "windows")'.dependencies]
diff --git a/src/uucore/src/lib/features/fsext.rs b/src/uucore/src/lib/features/fsext.rs
index b8207d68c..cf17067e8 100644
--- a/src/uucore/src/lib/features/fsext.rs
+++ b/src/uucore/src/lib/features/fsext.rs
@@ -90,6 +90,8 @@ pub use libc::statfs as StatFs;
     target_os = "netbsd",
     target_os = "bitrig",
     target_os = "dragonfly",
+    target_os = "illumos",
+    target_os = "solaris",
     target_os = "redox"
 ))]
 pub use libc::statvfs as StatFs;
@@ -100,13 +102,15 @@ pub use libc::statvfs as StatFs;
     target_os = "android",
     target_os = "freebsd",
     target_os = "openbsd",
+    target_os = "redox"
 ))]
 pub use libc::statfs as statfs_fn;
 #[cfg(any(
     target_os = "netbsd",
     target_os = "bitrig",
-    target_os = "dragonfly",
-    target_os = "redox"
+    target_os = "illumos",
+    target_os = "solaris",
+    target_os = "dragonfly"
 ))]
 pub use libc::statvfs as statfs_fn;
 
@@ -476,7 +480,7 @@ pub fn read_fs_list() -> Vec<MountInfo> {
         }
         mounts
     }
-    #[cfg(target_os = "redox")]
+    #[cfg(any(target_os = "redox", target_os = "illumos", target_os = "solaris"))]
     {
         // No method to read mounts, yet
         Vec::new()
diff --git a/src/uucore/src/lib/features/perms.rs b/src/uucore/src/lib/features/perms.rs
index 942c67e29..d8e345313 100644
--- a/src/uucore/src/lib/features/perms.rs
+++ b/src/uucore/src/lib/features/perms.rs
@@ -12,9 +12,9 @@ use crate::error::USimpleError;
 pub use crate::features::entries;
 use crate::fs::resolve_relative_path;
 use crate::show_error;
-use clap::App;
 use clap::Arg;
 use clap::ArgMatches;
+use clap::Command;
 use libc::{self, gid_t, uid_t};
 use walkdir::WalkDir;
 
@@ -383,6 +383,7 @@ impl ChownExecutor {
 }
 
 pub mod options {
+    pub const HELP: &str = "help";
     pub mod verbosity {
         pub const CHANGES: &str = "changes";
         pub const QUIET: &str = "quiet";
@@ -414,13 +415,13 @@ type GidUidFilterParser = fn(&ArgMatches) -> UResult<(Option<u32>, Option<u32>,
 
 /// Base implementation for `chgrp` and `chown`.
 ///
-/// An argument called `add_arg_if_not_reference` will be added to `app` if
+/// An argument called `add_arg_if_not_reference` will be added to `command` if
 /// `args` does not contain the `--reference` option.
 /// `parse_gid_uid_and_filter` will be called to obtain the target gid and uid, and the filter,
 /// from `ArgMatches`.
 /// `groups_only` determines whether verbose output will only mention the group.
 pub fn chown_base<'a>(
-    mut app: App<'a>,
+    mut command: Command<'a>,
     args: impl crate::Args,
     add_arg_if_not_reference: &'a str,
     parse_gid_uid_and_filter: GidUidFilterParser,
@@ -444,7 +445,7 @@ pub fn chown_base<'a>(
     if help || !reference {
         // add both positional arguments
         // arg_group is only required if
-        app = app.arg(
+        command = command.arg(
             Arg::new(add_arg_if_not_reference)
                 .value_name(add_arg_if_not_reference)
                 .required(true)
@@ -452,7 +453,7 @@ pub fn chown_base<'a>(
                 .multiple_occurrences(false),
         );
     }
-    app = app.arg(
+    command = command.arg(
         Arg::new(options::ARG_FILES)
             .value_name(options::ARG_FILES)
             .multiple_occurrences(true)
@@ -460,7 +461,7 @@ pub fn chown_base<'a>(
             .required(true)
             .min_values(1),
     );
-    let matches = app.get_matches_from(args);
+    let matches = command.get_matches_from(args);
 
     let files: Vec<String> = matches
         .values_of(options::ARG_FILES)
diff --git a/src/uucore/src/lib/features/tokenize/num_format/formatters/decf.rs b/src/uucore/src/lib/features/tokenize/num_format/formatters/decf.rs
index 52b8515c9..07e1b3f47 100644
--- a/src/uucore/src/lib/features/tokenize/num_format/formatters/decf.rs
+++ b/src/uucore/src/lib/features/tokenize/num_format/formatters/decf.rs
@@ -5,21 +5,132 @@ use super::super::format_field::FormatField;
 use super::super::formatter::{FormatPrimitive, Formatter, InitialPrefix};
 use super::float_common::{get_primitive_dec, primitive_to_str_common, FloatAnalysis};
 
-fn get_len_fmt_primitive(fmt: &FormatPrimitive) -> usize {
-    let mut len = 0;
-    if let Some(ref s) = fmt.prefix {
-        len += s.len();
+const SIGNIFICANT_FIGURES: usize = 6;
+
+// Parse a numeric string as the nearest integer with a given significance.
+// This is a helper function for round().
+// Examples:
+//  round_to_significance("456", 1) == 500
+//  round_to_significance("456", 2) == 460
+//  round_to_significance("456", 9) == 456
+fn round_to_significance(input: &str, significant_figures: usize) -> u32 {
+    if significant_figures < input.len() {
+        // If the input has too many digits, use a float intermediary
+        // to round it before converting to an integer. Otherwise,
+        // converting straight to integer will truncate.
+        // There might be a cleaner way to do this...
+        let digits = &input[..significant_figures + 1];
+        let float_representation = digits.parse::<f32>().unwrap();
+        (float_representation / 10.0).round() as u32
+    } else {
+        input.parse::<u32>().unwrap_or(0)
     }
-    if let Some(ref s) = fmt.pre_decimal {
-        len += s.len();
+}
+
+// Removing trailing zeroes, expressing the result as an integer where
+// possible. This is a helper function for round().
+fn truncate(mut format: FormatPrimitive) -> FormatPrimitive {
+    if let Some(ref post_dec) = format.post_decimal {
+        let trimmed = post_dec.trim_end_matches('0');
+
+        if trimmed.is_empty() {
+            // If there are no nonzero digits after the decimal point,
+            // use integer formatting by clearing post_decimal and suffix.
+            format.post_decimal = Some("".into());
+            if format.suffix == Some("e+00".into()) {
+                format.suffix = Some("".into());
+            }
+        } else if trimmed.len() != post_dec.len() {
+            // Otherwise, update the format to remove only the trailing
+            // zeroes (e.g. "4.50" becomes "4.5", not "4"). If there were
+            // no trailing zeroes, do nothing.
+            format.post_decimal = Some(trimmed.to_owned());
+        }
     }
-    if let Some(ref s) = fmt.post_decimal {
-        len += s.len();
+    format
+}
+
+// Round a format to six significant figures and remove trailing zeroes.
+fn round(mut format: FormatPrimitive) -> FormatPrimitive {
+    let mut significant_digits_remaining = SIGNIFICANT_FIGURES;
+
+    // First, take as many significant digits as possible from pre_decimal,
+    if format.pre_decimal.is_some() {
+        let input = format.pre_decimal.as_ref().unwrap();
+        let rounded = round_to_significance(input, significant_digits_remaining);
+        let mut rounded_str = rounded.to_string();
+        significant_digits_remaining -= rounded_str.len();
+
+        // If the pre_decimal has exactly enough significant digits,
+        // round the input to the nearest integer. If the first
+        // post_decimal digit is 5 or higher, round up by incrementing
+        // the pre_decimal number. Otherwise, use the pre_decimal as-is.
+        if significant_digits_remaining == 0 {
+            if let Some(digits) = &format.post_decimal {
+                if digits.chars().next().unwrap_or('0') >= '5' {
+                    let rounded = rounded + 1;
+                    rounded_str = rounded.to_string();
+                }
+            }
+        }
+        format.pre_decimal = Some(rounded_str);
     }
-    if let Some(ref s) = fmt.suffix {
-        len += s.len();
+
+    // If no significant digits remain, or there's no post_decimal to
+    // round, return the rounded pre_decimal value with no post_decimal.
+    // Otherwise, round the post_decimal to the remaining significance.
+    if significant_digits_remaining == 0 {
+        format.post_decimal = Some(String::new());
+    } else if let Some(input) = format.post_decimal {
+        let leading_zeroes = input.len() - input.trim_start_matches('0').len();
+        let digits = &input[leading_zeroes..];
+
+        // In the post_decimal, leading zeroes are significant. "01.0010"
+        // has one significant digit in pre_decimal, and 3 from post_decimal.
+        let mut post_decimal_str = String::with_capacity(significant_digits_remaining);
+        for _ in 0..leading_zeroes {
+            post_decimal_str.push('0');
+        }
+
+        if leading_zeroes < significant_digits_remaining {
+            // After significant leading zeroes, round the remaining digits
+            // to any remaining significance.
+            let rounded = round_to_significance(digits, significant_digits_remaining);
+            post_decimal_str.push_str(&rounded.to_string());
+        } else if leading_zeroes == significant_digits_remaining
+            && digits.chars().next().unwrap_or('0') >= '5'
+        {
+            // If necessary, round up the post_decimal ("1.000009" should
+            // round to 1.00001, instead of truncating after the last
+            // significant leading zero).
+            post_decimal_str.pop();
+            post_decimal_str.push('1');
+        } else {
+            // If the rounded post_decimal is entirely zeroes, discard
+            // it and use integer formatting instead.
+            post_decimal_str = "".into();
+        }
+
+        format.post_decimal = Some(post_decimal_str);
+    }
+    truncate(format)
+}
+
+// Given an exponent used in scientific notation, return whether the
+// number is small enough to be expressed as a decimal instead. "Small
+// enough" is based only on the number's magnitude, not the length of
+// any string representation.
+fn should_represent_as_decimal(suffix: &Option<String>) -> bool {
+    match suffix {
+        Some(exponent) => {
+            if exponent.chars().nth(1) == Some('-') {
+                exponent < &"e-05".into()
+            } else {
+                exponent < &"e+06".into()
+            }
+        }
+        None => true,
     }
-    len
 }
 
 pub struct Decf;
@@ -46,34 +157,27 @@ impl Formatter for Decf {
             None,
             false,
         );
-        let mut f_sci = get_primitive_dec(
+        let mut f_dec = get_primitive_dec(
             initial_prefix,
             &str_in[initial_prefix.offset..],
             &analysis,
             second_field as usize,
             Some(*field.field_char == 'G'),
         );
-        // strip trailing zeroes
-        if let Some(ref post_dec) = f_sci.post_decimal {
-            let trimmed = post_dec.trim_end_matches('0');
-            if trimmed.len() != post_dec.len() {
-                f_sci.post_decimal = Some(trimmed.to_owned());
-            }
+
+        if should_represent_as_decimal(&f_dec.suffix) {
+            // Use decimal formatting instead of scientific notation
+            // if the input's magnitude is small.
+            f_dec = get_primitive_dec(
+                initial_prefix,
+                &str_in[initial_prefix.offset..],
+                &analysis,
+                second_field as usize,
+                None,
+            );
         }
-        let f_fl = get_primitive_dec(
-            initial_prefix,
-            &str_in[initial_prefix.offset..],
-            &analysis,
-            second_field as usize,
-            None,
-        );
-        Some(
-            if get_len_fmt_primitive(&f_fl) >= get_len_fmt_primitive(&f_sci) {
-                f_sci
-            } else {
-                f_fl
-            },
-        )
+
+        Some(round(f_dec))
     }
     fn primitive_to_str(&self, prim: &FormatPrimitive, field: FormatField) -> String {
         primitive_to_str_common(prim, &field)
diff --git a/src/uucore/src/lib/mods/backup_control.rs b/src/uucore/src/lib/mods/backup_control.rs
index a2753b964..f2da374b6 100644
--- a/src/uucore/src/lib/mods/backup_control.rs
+++ b/src/uucore/src/lib/mods/backup_control.rs
@@ -34,16 +34,16 @@
 //! #[macro_use]
 //! extern crate uucore;
 //!
-//! use clap::{App, Arg, ArgMatches};
+//! use clap::{Command, Arg, ArgMatches};
 //! use std::path::{Path, PathBuf};
 //! use uucore::backup_control::{self, BackupMode};
 //! use uucore::error::{UError, UResult};
 //!
 //! fn main() {
-//!     let usage = String::from("app [OPTION]... ARG");
+//!     let usage = String::from("command [OPTION]... ARG");
 //!     let long_usage = String::from("And here's a detailed explanation");
 //!
-//!     let matches = App::new("app")
+//!     let matches = Command::new("command")
 //!         .arg(backup_control::arguments::backup())
 //!         .arg(backup_control::arguments::backup_no_args())
 //!         .arg(backup_control::arguments::suffix())
@@ -54,7 +54,7 @@
 //!             backup_control::BACKUP_CONTROL_LONG_HELP
 //!         ))
 //!         .get_matches_from(vec![
-//!             "app", "--backup=t", "--suffix=bak~"
+//!             "command", "--backup=t", "--suffix=bak~"
 //!         ]);
 //!
 //!     let backup_mode = match backup_control::determine_backup_mode(&matches) {
@@ -290,14 +290,14 @@ pub fn determine_backup_suffix(matches: &ArgMatches) -> String {
 /// #[macro_use]
 /// extern crate uucore;
 /// use uucore::backup_control::{self, BackupMode};
-/// use clap::{App, Arg, ArgMatches};
+/// use clap::{Command, Arg, ArgMatches};
 ///
 /// fn main() {
-///     let matches = App::new("app")
+///     let matches = Command::new("command")
 ///         .arg(backup_control::arguments::backup())
 ///         .arg(backup_control::arguments::backup_no_args())
 ///         .get_matches_from(vec![
-///             "app", "-b", "--backup=t"
+///             "command", "-b", "--backup=t"
 ///         ]);
 ///
 ///     let backup_mode = backup_control::determine_backup_mode(&matches).unwrap();
@@ -313,14 +313,14 @@ pub fn determine_backup_suffix(matches: &ArgMatches) -> String {
 /// #[macro_use]
 /// extern crate uucore;
 /// use uucore::backup_control::{self, BackupMode, BackupError};
-/// use clap::{App, Arg, ArgMatches};
+/// use clap::{Command, Arg, ArgMatches};
 ///
 /// fn main() {
-///     let matches = App::new("app")
+///     let matches = Command::new("command")
 ///         .arg(backup_control::arguments::backup())
 ///         .arg(backup_control::arguments::backup_no_args())
 ///         .get_matches_from(vec![
-///             "app", "-b", "--backup=n"
+///             "command", "-b", "--backup=n"
 ///         ]);
 ///
 ///     let backup_mode = backup_control::determine_backup_mode(&matches);
@@ -446,7 +446,7 @@ mod tests {
     use super::*;
     use std::env;
     // Required to instantiate mutex in shared context
-    use clap::App;
+    use clap::Command;
     use lazy_static::lazy_static;
     use std::sync::Mutex;
 
@@ -463,8 +463,8 @@ mod tests {
     // Environment variable for "VERSION_CONTROL"
     static ENV_VERSION_CONTROL: &str = "VERSION_CONTROL";
 
-    fn make_app() -> clap::App<'static> {
-        App::new("app")
+    fn make_app() -> clap::Command<'static> {
+        Command::new("command")
             .arg(arguments::backup())
             .arg(arguments::backup_no_args())
             .arg(arguments::suffix())
@@ -474,7 +474,7 @@ mod tests {
     #[test]
     fn test_backup_mode_short_only() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "-b"]);
+        let matches = make_app().get_matches_from(vec!["command", "-b"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -485,7 +485,7 @@ mod tests {
     #[test]
     fn test_backup_mode_long_preferred_over_short() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "-b", "--backup=none"]);
+        let matches = make_app().get_matches_from(vec!["command", "-b", "--backup=none"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -496,7 +496,7 @@ mod tests {
     #[test]
     fn test_backup_mode_long_without_args_no_env() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "--backup"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -507,7 +507,7 @@ mod tests {
     #[test]
     fn test_backup_mode_long_with_args() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "--backup=simple"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup=simple"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -518,7 +518,7 @@ mod tests {
     #[test]
     fn test_backup_mode_long_with_args_invalid() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "--backup=foobar"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup=foobar"]);
 
         let result = determine_backup_mode(&matches);
 
@@ -531,7 +531,7 @@ mod tests {
     #[test]
     fn test_backup_mode_long_with_args_ambiguous() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "--backup=n"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup=n"]);
 
         let result = determine_backup_mode(&matches);
 
@@ -544,7 +544,7 @@ mod tests {
     #[test]
     fn test_backup_mode_long_with_arg_shortened() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "--backup=si"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup=si"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -556,7 +556,7 @@ mod tests {
     fn test_backup_mode_short_only_ignore_env() {
         let _dummy = TEST_MUTEX.lock().unwrap();
         env::set_var(ENV_VERSION_CONTROL, "none");
-        let matches = make_app().get_matches_from(vec!["app", "-b"]);
+        let matches = make_app().get_matches_from(vec!["command", "-b"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -569,7 +569,7 @@ mod tests {
     fn test_backup_mode_long_without_args_with_env() {
         let _dummy = TEST_MUTEX.lock().unwrap();
         env::set_var(ENV_VERSION_CONTROL, "none");
-        let matches = make_app().get_matches_from(vec!["app", "--backup"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -582,7 +582,7 @@ mod tests {
     fn test_backup_mode_long_with_env_var_invalid() {
         let _dummy = TEST_MUTEX.lock().unwrap();
         env::set_var(ENV_VERSION_CONTROL, "foobar");
-        let matches = make_app().get_matches_from(vec!["app", "--backup"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup"]);
 
         let result = determine_backup_mode(&matches);
 
@@ -597,7 +597,7 @@ mod tests {
     fn test_backup_mode_long_with_env_var_ambiguous() {
         let _dummy = TEST_MUTEX.lock().unwrap();
         env::set_var(ENV_VERSION_CONTROL, "n");
-        let matches = make_app().get_matches_from(vec!["app", "--backup"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup"]);
 
         let result = determine_backup_mode(&matches);
 
@@ -612,7 +612,7 @@ mod tests {
     fn test_backup_mode_long_with_env_var_shortened() {
         let _dummy = TEST_MUTEX.lock().unwrap();
         env::set_var(ENV_VERSION_CONTROL, "si");
-        let matches = make_app().get_matches_from(vec!["app", "--backup"]);
+        let matches = make_app().get_matches_from(vec!["command", "--backup"]);
 
         let result = determine_backup_mode(&matches).unwrap();
 
@@ -623,7 +623,7 @@ mod tests {
     #[test]
     fn test_suffix_takes_hyphen_value() {
         let _dummy = TEST_MUTEX.lock().unwrap();
-        let matches = make_app().get_matches_from(vec!["app", "-b", "--suffix", "-v"]);
+        let matches = make_app().get_matches_from(vec!["command", "-b", "--suffix", "-v"]);
 
         let result = determine_backup_suffix(&matches);
         assert_eq!(result, "-v");
diff --git a/src/uucore/src/lib/mods/error.rs b/src/uucore/src/lib/mods/error.rs
index ba7722f1c..dbe4d5bc1 100644
--- a/src/uucore/src/lib/mods/error.rs
+++ b/src/uucore/src/lib/mods/error.rs
@@ -50,6 +50,7 @@
 
 // spell-checker:ignore uioerror
 
+use clap;
 use std::{
     error::Error,
     fmt::{Display, Formatter},
@@ -615,3 +616,13 @@ impl From<i32> for Box<dyn UError> {
         ExitCode::new(i)
     }
 }
+
+/// Implementations for clap::Error
+impl UError for clap::Error {
+    fn code(&self) -> i32 {
+        match self.kind() {
+            clap::ErrorKind::DisplayHelp | clap::ErrorKind::DisplayVersion => 0,
+            _ => 1,
+        }
+    }
+}
diff --git a/src/uucore/src/lib/parser/parse_time.rs b/src/uucore/src/lib/parser/parse_time.rs
index 366eebdea..79387c0b1 100644
--- a/src/uucore/src/lib/parser/parse_time.rs
+++ b/src/uucore/src/lib/parser/parse_time.rs
@@ -63,6 +63,10 @@ pub fn from_str(string: &str) -> Result<Duration, String> {
         .parse::<f64>()
         .map_err(|e| format!("invalid time interval {}: {}", string.quote(), e))?;
 
+    if num < 0. {
+        return Err(format!("invalid time interval {}", string.quote()));
+    }
+
     const NANOS_PER_SEC: u32 = 1_000_000_000;
     let whole_secs = num.trunc();
     let nanos = (num.fract() * (NANOS_PER_SEC as f64)).trunc();
@@ -105,4 +109,9 @@ mod tests {
     fn test_error_invalid_magnitude() {
         assert!(from_str("12abc3s").is_err());
     }
+
+    #[test]
+    fn test_negative() {
+        assert!(from_str("-1").is_err());
+    }
 }
diff --git a/tests/by-util/test_cp.rs b/tests/by-util/test_cp.rs
index 9ee76bb5e..11afa469e 100644
--- a/tests/by-util/test_cp.rs
+++ b/tests/by-util/test_cp.rs
@@ -183,6 +183,16 @@ fn test_cp_arg_no_target_directory() {
         .stderr_contains("cannot overwrite directory");
 }
 
+#[test]
+fn test_cp_target_directory_is_file() {
+    new_ucmd!()
+        .arg("-t")
+        .arg(TEST_HOW_ARE_YOU_SOURCE)
+        .arg(TEST_HELLO_WORLD_SOURCE)
+        .fails()
+        .stderr_contains(format!("'{}' is not a directory", TEST_HOW_ARE_YOU_SOURCE));
+}
+
 #[test]
 fn test_cp_arg_interactive() {
     new_ucmd!()
diff --git a/tests/by-util/test_dd.rs b/tests/by-util/test_dd.rs
index acf63bec7..f6287a940 100644
--- a/tests/by-util/test_dd.rs
+++ b/tests/by-util/test_dd.rs
@@ -1,4 +1,4 @@
-// spell-checker:ignore fname, tname, fpath, specfile, testfile, unspec, ifile, ofile, outfile, fullblock, urand, fileio, atoe, atoibm, availible, behaviour, bmax, bremain, btotal, cflags, creat, ctable, ctty, datastructures, doesnt, etoa, fileout, fname, gnudd, iconvflags, nocache, noctty, noerror, nofollow, nolinks, nonblock, oconvflags, outfile, parseargs, rlen, rmax, rposition, rremain, rsofar, rstat, sigusr, sigval, wlen, wstat abcdefghijklm abcdefghi nabcde nabcdefg abcdefg
+// spell-checker:ignore fname, tname, fpath, specfile, testfile, unspec, ifile, ofile, outfile, fullblock, urand, fileio, atoe, atoibm, availible, behaviour, bmax, bremain, btotal, cflags, creat, ctable, ctty, datastructures, doesnt, etoa, fileout, fname, gnudd, iconvflags, iseek, nocache, noctty, noerror, nofollow, nolinks, nonblock, oconvflags, oseek, outfile, parseargs, rlen, rmax, rposition, rremain, rsofar, rstat, sigusr, sigval, wlen, wstat abcdefghijklm abcdefghi nabcde nabcdefg abcdefg
 
 use crate::common::util::*;
 
@@ -1139,3 +1139,48 @@ fn test_block_sync() {
         .stdout_is("012  abcde     ")
         .stderr_is("2+1 records in\n0+1 records out\n1 truncated record\n");
 }
+
+#[test]
+fn test_bytes_iseek_bytes_iflag() {
+    new_ucmd!()
+        .args(&["iseek=10", "iflag=skip_bytes", "bs=2"])
+        .pipe_in("0123456789abcdefghijklm")
+        .succeeds()
+        .stdout_is("abcdefghijklm");
+}
+
+#[test]
+fn test_bytes_iseek_skip_additive() {
+    new_ucmd!()
+        .args(&["iseek=5", "skip=5", "iflag=skip_bytes", "bs=2"])
+        .pipe_in("0123456789abcdefghijklm")
+        .succeeds()
+        .stdout_is("abcdefghijklm");
+}
+
+#[test]
+fn test_bytes_oseek_bytes_oflag() {
+    new_ucmd!()
+        .args(&["oseek=8", "oflag=seek_bytes", "bs=2"])
+        .pipe_in("abcdefghijklm")
+        .succeeds()
+        .stdout_is_fixture_bytes("dd-bytes-alphabet-null.spec");
+}
+
+#[test]
+fn test_bytes_oseek_bytes_trunc_oflag() {
+    new_ucmd!()
+        .args(&["oseek=8", "oflag=seek_bytes", "bs=2", "count=0"])
+        .pipe_in("abcdefghijklm")
+        .succeeds()
+        .stdout_is_fixture_bytes("dd-bytes-null-trunc.spec");
+}
+
+#[test]
+fn test_bytes_oseek_seek_additive() {
+    new_ucmd!()
+        .args(&["oseek=4", "seek=4", "oflag=seek_bytes", "bs=2"])
+        .pipe_in("abcdefghijklm")
+        .succeeds()
+        .stdout_is_fixture_bytes("dd-bytes-alphabet-null.spec");
+}
diff --git a/tests/by-util/test_link.rs b/tests/by-util/test_link.rs
index 5a84364e9..6e98f1d64 100644
--- a/tests/by-util/test_link.rs
+++ b/tests/by-util/test_link.rs
@@ -45,7 +45,7 @@ fn test_link_one_argument() {
     let (_, mut ucmd) = at_and_ucmd!();
     let file = "test_link_argument";
     ucmd.args(&[file]).fails().stderr_contains(
-        "error: The argument '<FILES>...' requires at least 2 values, but only 1 was provide",
+        "error: The argument '<FILES>...' requires at least 2 values but only 1 was provided",
     );
 }
 
diff --git a/tests/by-util/test_ls.rs b/tests/by-util/test_ls.rs
index bb3b24670..3cfba4312 100644
--- a/tests/by-util/test_ls.rs
+++ b/tests/by-util/test_ls.rs
@@ -2869,3 +2869,47 @@ fn test_ls_context_format() {
             );
     }
 }
+
+#[test]
+#[allow(non_snake_case)]
+fn test_ls_a_A() {
+    let scene = TestScenario::new(util_name!());
+
+    scene
+        .ucmd()
+        .arg("-A")
+        .arg("-a")
+        .succeeds()
+        .stdout_contains(".")
+        .stdout_contains("..");
+
+    scene
+        .ucmd()
+        .arg("-a")
+        .arg("-A")
+        .succeeds()
+        .stdout_does_not_contain(".")
+        .stdout_does_not_contain("..");
+}
+
+#[test]
+#[allow(non_snake_case)]
+fn test_ls_multiple_a_A() {
+    let scene = TestScenario::new(util_name!());
+
+    scene
+        .ucmd()
+        .arg("-a")
+        .arg("-a")
+        .succeeds()
+        .stdout_contains(".")
+        .stdout_contains("..");
+
+    scene
+        .ucmd()
+        .arg("-A")
+        .arg("-A")
+        .succeeds()
+        .stdout_does_not_contain(".")
+        .stdout_does_not_contain("..");
+}
diff --git a/tests/by-util/test_mknod.rs b/tests/by-util/test_mknod.rs
index f42ab0b90..3b22ef835 100644
--- a/tests/by-util/test_mknod.rs
+++ b/tests/by-util/test_mknod.rs
@@ -86,14 +86,14 @@ fn test_mknod_character_device_requires_major_and_minor() {
         .arg("1")
         .arg("c")
         .fails()
-        .stderr_contains(&"Invalid value for '<MINOR>'");
+        .stderr_contains(&"Invalid value \"c\" for '<MINOR>'");
     new_ucmd!()
         .arg("test_file")
         .arg("c")
         .arg("c")
         .arg("1")
         .fails()
-        .stderr_contains(&"Invalid value for '<MAJOR>'");
+        .stderr_contains(&"Invalid value \"c\" for '<MAJOR>'");
 }
 
 #[test]
diff --git a/tests/by-util/test_nproc.rs b/tests/by-util/test_nproc.rs
index 5657e6b7e..330f327cb 100644
--- a/tests/by-util/test_nproc.rs
+++ b/tests/by-util/test_nproc.rs
@@ -20,7 +20,7 @@ fn test_nproc_all_omp() {
         .succeeds();
 
     let nproc_omp: u8 = result.stdout_str().trim().parse().unwrap();
-    assert!(nproc_omp == 60);
+    assert_eq!(nproc_omp, 60);
 
     let result = TestScenario::new(util_name!())
         .ucmd_keepenv()
@@ -28,7 +28,7 @@ fn test_nproc_all_omp() {
         .arg("--all")
         .succeeds();
     let nproc_omp: u8 = result.stdout_str().trim().parse().unwrap();
-    assert!(nproc == nproc_omp);
+    assert_eq!(nproc, nproc_omp);
 
     // If the parsing fails, returns the number of CPU
     let result = TestScenario::new(util_name!())
@@ -36,7 +36,7 @@ fn test_nproc_all_omp() {
         .env("OMP_NUM_THREADS", "incorrectnumber") // returns the number CPU
         .succeeds();
     let nproc_omp: u8 = result.stdout_str().trim().parse().unwrap();
-    assert!(nproc == nproc_omp);
+    assert_eq!(nproc, nproc_omp);
 }
 
 #[test]
@@ -51,14 +51,14 @@ fn test_nproc_ignore() {
             .arg((nproc_total - 1).to_string())
             .succeeds();
         let nproc: u8 = result.stdout_str().trim().parse().unwrap();
-        assert!(nproc == 1);
+        assert_eq!(nproc, 1);
         // Ignore all CPU but one with a string
         let result = TestScenario::new(util_name!())
             .ucmd_keepenv()
             .arg("--ignore= 1")
             .succeeds();
         let nproc: u8 = result.stdout_str().trim().parse().unwrap();
-        assert!(nproc_total - 1 == nproc);
+        assert_eq!(nproc_total - 1, nproc);
     }
 }
 
@@ -70,5 +70,99 @@ fn test_nproc_ignore_all_omp() {
         .arg("--ignore=40")
         .succeeds();
     let nproc: u8 = result.stdout_str().trim().parse().unwrap();
-    assert!(nproc == 2);
+    assert_eq!(nproc, 2);
+}
+
+#[test]
+fn test_nproc_omp_limit() {
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "42")
+        .env("OMP_THREAD_LIMIT", "0")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(nproc, 42);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "42")
+        .env("OMP_THREAD_LIMIT", "2")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(nproc, 2);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "42")
+        .env("OMP_THREAD_LIMIT", "2bad")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(nproc, 42);
+
+    let result = new_ucmd!().arg("--all").succeeds();
+    let nproc_system: u8 = result.stdout_str().trim().parse().unwrap();
+    assert!(nproc_system > 0);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_THREAD_LIMIT", "1")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(nproc, 1);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "0")
+        .env("OMP_THREAD_LIMIT", "")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(nproc, nproc_system);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "")
+        .env("OMP_THREAD_LIMIT", "")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(nproc, nproc_system);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "2,2,1")
+        .env("OMP_THREAD_LIMIT", "")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(2, nproc);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "2,ignored")
+        .env("OMP_THREAD_LIMIT", "")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(2, nproc);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "2,2,1")
+        .env("OMP_THREAD_LIMIT", "0")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(2, nproc);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "2,2,1")
+        .env("OMP_THREAD_LIMIT", "1bad")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(2, nproc);
+
+    let result = TestScenario::new(util_name!())
+        .ucmd_keepenv()
+        .env("OMP_NUM_THREADS", "29,2,1")
+        .env("OMP_THREAD_LIMIT", "1bad")
+        .succeeds();
+    let nproc: u8 = result.stdout_str().trim().parse().unwrap();
+    assert_eq!(29, nproc);
 }
diff --git a/tests/by-util/test_printf.rs b/tests/by-util/test_printf.rs
index 72ca4535a..d5be4cd17 100644
--- a/tests/by-util/test_printf.rs
+++ b/tests/by-util/test_printf.rs
@@ -289,7 +289,7 @@ fn sub_num_dec_trunc() {
     new_ucmd!()
         .args(&["pi is ~ %g", "3.1415926535"])
         .succeeds()
-        .stdout_only("pi is ~ 3.141593");
+        .stdout_only("pi is ~ 3.14159");
 }
 
 #[cfg_attr(not(feature = "test_unimplemented"), ignore)]
@@ -469,3 +469,56 @@ fn sub_float_leading_zeroes() {
         .succeeds()
         .stdout_only("001.000000");
 }
+
+#[test]
+fn sub_general_float() {
+    new_ucmd!()
+        .args(&["%g", "1.1"])
+        .succeeds()
+        .stdout_only("1.1");
+}
+
+#[test]
+fn sub_general_truncate_to_integer() {
+    new_ucmd!().args(&["%g", "1.0"]).succeeds().stdout_only("1");
+}
+
+#[test]
+fn sub_general_scientific_notation() {
+    new_ucmd!()
+        .args(&["%g", "1000010"])
+        .succeeds()
+        .stdout_only("1.00001e+06");
+}
+
+#[test]
+fn sub_general_round_scientific_notation() {
+    new_ucmd!()
+        .args(&["%g", "123456789"])
+        .succeeds()
+        .stdout_only("1.23457e+08");
+}
+
+#[test]
+fn sub_general_round_float() {
+    new_ucmd!()
+        .args(&["%g", "12345.6789"])
+        .succeeds()
+        .stdout_only("12345.7");
+}
+
+#[test]
+fn sub_general_round_float_to_integer() {
+    new_ucmd!()
+        .args(&["%g", "123456.7"])
+        .succeeds()
+        .stdout_only("123457");
+}
+
+#[test]
+fn sub_general_round_float_leading_zeroes() {
+    new_ucmd!()
+        .args(&["%g", "1.000009"])
+        .succeeds()
+        .stdout_only("1.00001");
+}
diff --git a/tests/by-util/test_sleep.rs b/tests/by-util/test_sleep.rs
index d33143ae0..c7c6b3af1 100644
--- a/tests/by-util/test_sleep.rs
+++ b/tests/by-util/test_sleep.rs
@@ -3,6 +3,14 @@ use crate::common::util::*;
 
 use std::time::{Duration, Instant};
 
+#[test]
+fn test_invalid_time_interval() {
+    new_ucmd!()
+        .arg("xyz")
+        .fails()
+        .usage_error("invalid time interval 'xyz'");
+}
+
 #[test]
 fn test_sleep_no_suffix() {
     let millis_100 = Duration::from_millis(100);
@@ -141,3 +149,11 @@ fn test_sum_overflow() {
         .no_stderr()
         .no_stdout();
 }
+
+#[test]
+fn test_negative_interval() {
+    new_ucmd!()
+        .args(&["--", "-1"])
+        .fails()
+        .usage_error("invalid time interval '-1'");
+}
diff --git a/tests/by-util/test_split.rs b/tests/by-util/test_split.rs
index 642cb7c68..87c37787e 100644
--- a/tests/by-util/test_split.rs
+++ b/tests/by-util/test_split.rs
@@ -571,6 +571,19 @@ fn test_elide_empty_files() {
     assert!(!at.plus("xad").exists());
 }
 
+#[test]
+#[cfg(unix)]
+fn test_elide_dev_null() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    ucmd.args(&["-e", "-n", "3", "/dev/null"])
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert!(!at.plus("xaa").exists());
+    assert!(!at.plus("xab").exists());
+    assert!(!at.plus("xac").exists());
+}
+
 #[test]
 fn test_lines() {
     let (at, mut ucmd) = at_and_ucmd!();
@@ -605,3 +618,40 @@ fn test_line_bytes() {
     assert_eq!(at.read("xac"), "cccc\ndd\n");
     assert_eq!(at.read("xad"), "ee\n");
 }
+
+#[test]
+fn test_line_bytes_no_final_newline() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    ucmd.args(&["-C", "2"])
+        .pipe_in("1\n2222\n3\n4")
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert_eq!(at.read("xaa"), "1\n");
+    assert_eq!(at.read("xab"), "22");
+    assert_eq!(at.read("xac"), "22");
+    assert_eq!(at.read("xad"), "\n");
+    assert_eq!(at.read("xae"), "3\n");
+    assert_eq!(at.read("xaf"), "4");
+}
+
+#[test]
+fn test_line_bytes_no_empty_file() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    ucmd.args(&["-C", "1"])
+        .pipe_in("1\n2222\n3\n4")
+        .succeeds()
+        .no_stdout()
+        .no_stderr();
+    assert_eq!(at.read("xaa"), "1");
+    assert_eq!(at.read("xab"), "\n");
+    assert_eq!(at.read("xac"), "2");
+    assert_eq!(at.read("xad"), "2");
+    assert_eq!(at.read("xae"), "2");
+    assert_eq!(at.read("xaf"), "2");
+    assert_eq!(at.read("xag"), "\n");
+    assert_eq!(at.read("xah"), "3");
+    assert_eq!(at.read("xai"), "\n");
+    assert_eq!(at.read("xaj"), "4");
+    assert!(!at.plus("xak").exists());
+}
diff --git a/tests/by-util/test_timeout.rs b/tests/by-util/test_timeout.rs
index 96a5b6a05..01ff85590 100644
--- a/tests/by-util/test_timeout.rs
+++ b/tests/by-util/test_timeout.rs
@@ -11,6 +11,14 @@ fn test_subcommand_return_code() {
     new_ucmd!().arg("1").arg("false").run().status_code(1);
 }
 
+#[test]
+fn test_invalid_time_interval() {
+    new_ucmd!()
+        .args(&["xyz", "sleep", "0"])
+        .fails()
+        .usage_error("invalid time interval 'xyz'");
+}
+
 #[test]
 fn test_command_with_args() {
     new_ucmd!()
@@ -81,3 +89,11 @@ fn test_dont_overflow() {
         .no_stderr()
         .no_stdout();
 }
+
+#[test]
+fn test_negative_interval() {
+    new_ucmd!()
+        .args(&["--", "-1", "sleep", "0"])
+        .fails()
+        .usage_error("invalid time interval '-1'");
+}
diff --git a/tests/fixtures/dd/dd-bytes-alphabet-null.spec b/tests/fixtures/dd/dd-bytes-alphabet-null.spec
new file mode 100644
index 000000000..1ab5429c1
Binary files /dev/null and b/tests/fixtures/dd/dd-bytes-alphabet-null.spec differ
diff --git a/tests/fixtures/dd/dd-bytes-null-trunc.spec b/tests/fixtures/dd/dd-bytes-null-trunc.spec
new file mode 100644
index 000000000..1b1cb4d44
Binary files /dev/null and b/tests/fixtures/dd/dd-bytes-null-trunc.spec differ