diff --git a/Cargo.lock b/Cargo.lock
index db334658a..f7fb30ba2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1882,7 +1882,7 @@ name = "whoami"
 version = "0.0.1"
 dependencies = [
  "advapi32-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "getopts 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "clap 2.31.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "uucore 0.0.1",
  "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1928,7 +1928,7 @@ dependencies = [
 name = "yes"
 version = "0.0.1"
 dependencies = [
- "getopts 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "clap 2.31.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "uucore 0.0.1",
 ]
 
diff --git a/src/arch/Cargo.toml b/src/arch/Cargo.toml
index 052233759..5d8703f80 100644
--- a/src/arch/Cargo.toml
+++ b/src/arch/Cargo.toml
@@ -10,10 +10,7 @@ path = "arch.rs"
 
 [dependencies]
 platform-info = { git = "https://github.com/uutils/platform-info" }
-
-[dependencies.uucore]
-path = "../uucore"
-default-features = false
+uucore = { path = "../uucore" }
 
 [[bin]]
 name = "arch"
diff --git a/src/base32/Cargo.toml b/src/base32/Cargo.toml
index 683f3f350..4ac1b296b 100644
--- a/src/base32/Cargo.toml
+++ b/src/base32/Cargo.toml
@@ -8,8 +8,9 @@ build = "../../mkmain.rs"
 name = "uu_base32"
 path = "base32.rs"
 
-[dependencies]
-uucore = { path="../uucore" }
+[dependencies.uucore]
+path = "../uucore"
+features = ["encoding"]
 
 [dependencies.clippy]
 version = "0.0.143"
diff --git a/src/base64/Cargo.toml b/src/base64/Cargo.toml
index 1c6e88171..dc25dea95 100644
--- a/src/base64/Cargo.toml
+++ b/src/base64/Cargo.toml
@@ -8,8 +8,9 @@ build = "../../mkmain.rs"
 name = "uu_base64"
 path = "base64.rs"
 
-[dependencies]
-uucore = { path="../uucore" }
+[dependencies.uucore]
+path = "../uucore"
+features = ["encoding"]
 
 [[bin]]
 name = "base64"
diff --git a/src/cat/Cargo.toml b/src/cat/Cargo.toml
index f0d52e9a0..135b8ddea 100644
--- a/src/cat/Cargo.toml
+++ b/src/cat/Cargo.toml
@@ -10,7 +10,10 @@ path = "cat.rs"
 
 [dependencies]
 quick-error = "1.1.0"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [target.'cfg(unix)'.dependencies]
 unix_socket = "0.5.0"
diff --git a/src/chgrp/Cargo.toml b/src/chgrp/Cargo.toml
index 6f338234e..08be38d9f 100644
--- a/src/chgrp/Cargo.toml
+++ b/src/chgrp/Cargo.toml
@@ -13,7 +13,6 @@ walkdir = "1.0.7"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries", "fs"]
 
 [[bin]]
diff --git a/src/chmod/Cargo.toml b/src/chmod/Cargo.toml
index f4b89c8ad..85760b5a2 100644
--- a/src/chmod/Cargo.toml
+++ b/src/chmod/Cargo.toml
@@ -10,9 +10,12 @@ path = "chmod.rs"
 
 [dependencies]
 libc = "0.2.26"
-uucore = { path="../uucore" }
 walker = "1.0.0"
 
+[dependencies.uucore]
+path = "../uucore"
+features = ["mode"]
+
 [[bin]]
 name = "chmod"
 path = "../../uumain.rs"
diff --git a/src/chown/Cargo.toml b/src/chown/Cargo.toml
index ceff8e315..7e94ada42 100644
--- a/src/chown/Cargo.toml
+++ b/src/chown/Cargo.toml
@@ -14,7 +14,6 @@ walkdir = "0.1"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries", "fs"]
 
 [dependencies.clippy]
diff --git a/src/chroot/Cargo.toml b/src/chroot/Cargo.toml
index 450d9e897..d5bcba708 100644
--- a/src/chroot/Cargo.toml
+++ b/src/chroot/Cargo.toml
@@ -13,7 +13,6 @@ getopts = "0.2.14"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries"]
 
 [[bin]]
diff --git a/src/cp/Cargo.toml b/src/cp/Cargo.toml
index 022843562..b529c40b7 100644
--- a/src/cp/Cargo.toml
+++ b/src/cp/Cargo.toml
@@ -17,9 +17,12 @@ libc = "0.2.26"
 walkdir = "1.0.7"
 clap = "2.20.0"
 quick-error = "1.1.0"
-uucore = { path="../uucore" }
 filetime = "0.1"
 
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
+
 [target.'cfg(target_os = "linux")'.dependencies]
 ioctl-sys = "0.5.2"
 
diff --git a/src/env/env.rs b/src/env/env.rs
index 1aa8520ff..8b7af61bf 100644
--- a/src/env/env.rs
+++ b/src/env/env.rs
@@ -9,7 +9,6 @@
  */
 
 /* last synced with: env (GNU coreutils) 8.13 */
-#![allow(non_camel_case_types)]
 
 #[macro_use]
 extern crate uucore;
@@ -25,7 +24,7 @@ static LONG_HELP: &'static str = "
  A mere - implies -i. If no COMMAND, print the resulting environment
 ";
 
-struct options {
+struct Options {
     ignore_env: bool,
     null: bool,
     unsets: Vec<String>,
@@ -52,7 +51,7 @@ pub fn uumain(args: Vec<String>) -> i32 {
         )
         .optopt("u", "unset", "remove variable from the environment", "NAME");
 
-    let mut opts = Box::new(options {
+    let mut opts = Box::new(Options {
         ignore_env: false,
         null: false,
         unsets: vec![],
diff --git a/src/groups/Cargo.toml b/src/groups/Cargo.toml
index 0d0ff38f8..71cf5ac52 100644
--- a/src/groups/Cargo.toml
+++ b/src/groups/Cargo.toml
@@ -10,7 +10,6 @@ path = "groups.rs"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries"]
 
 [[bin]]
diff --git a/src/id/Cargo.toml b/src/id/Cargo.toml
index 1e2f863b7..784cbfa35 100644
--- a/src/id/Cargo.toml
+++ b/src/id/Cargo.toml
@@ -10,7 +10,6 @@ path = "id.rs"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries", "process"]
 
 [[bin]]
diff --git a/src/kill/Cargo.toml b/src/kill/Cargo.toml
index 41d91294f..8a530c685 100644
--- a/src/kill/Cargo.toml
+++ b/src/kill/Cargo.toml
@@ -10,7 +10,10 @@ path = "kill.rs"
 
 [dependencies]
 libc = "0.2.26"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["signals"]
 
 [[bin]]
 name = "kill"
diff --git a/src/ls/Cargo.toml b/src/ls/Cargo.toml
index fa6ecec1d..05fa01611 100644
--- a/src/ls/Cargo.toml
+++ b/src/ls/Cargo.toml
@@ -19,7 +19,6 @@ unicode-width = "0.1.4"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries"]
 
 [[bin]]
diff --git a/src/nohup/Cargo.toml b/src/nohup/Cargo.toml
index 6be2c707c..0fecd736d 100644
--- a/src/nohup/Cargo.toml
+++ b/src/nohup/Cargo.toml
@@ -11,7 +11,10 @@ path = "nohup.rs"
 [dependencies]
 getopts = "0.2.14"
 libc = "0.2.26"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [[bin]]
 name = "nohup"
diff --git a/src/pinky/Cargo.toml b/src/pinky/Cargo.toml
index 7bd38dc77..2bac97232 100644
--- a/src/pinky/Cargo.toml
+++ b/src/pinky/Cargo.toml
@@ -10,7 +10,6 @@ path = "pinky.rs"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["utmpx", "entries"]
 
 [[bin]]
diff --git a/src/readlink/Cargo.toml b/src/readlink/Cargo.toml
index 42649257f..1e52942a0 100644
--- a/src/readlink/Cargo.toml
+++ b/src/readlink/Cargo.toml
@@ -11,7 +11,10 @@ path = "readlink.rs"
 [dependencies]
 getopts = "0.2.14"
 libc = "0.2.26"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [[bin]]
 name = "readlink"
diff --git a/src/realpath/Cargo.toml b/src/realpath/Cargo.toml
index affac2f83..1d7b30130 100644
--- a/src/realpath/Cargo.toml
+++ b/src/realpath/Cargo.toml
@@ -10,7 +10,10 @@ path = "realpath.rs"
 
 [dependencies]
 getopts = "0.2.14"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [[bin]]
 name = "realpath"
diff --git a/src/relpath/Cargo.toml b/src/relpath/Cargo.toml
index 402ac5888..69936f396 100644
--- a/src/relpath/Cargo.toml
+++ b/src/relpath/Cargo.toml
@@ -10,7 +10,10 @@ path = "relpath.rs"
 
 [dependencies]
 getopts = "0.2.14"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [[bin]]
 name = "relpath"
diff --git a/src/sleep/Cargo.toml b/src/sleep/Cargo.toml
index ad196cf7c..e4a7b014c 100644
--- a/src/sleep/Cargo.toml
+++ b/src/sleep/Cargo.toml
@@ -10,7 +10,10 @@ path = "sleep.rs"
 
 [dependencies]
 getopts = "0.2.14"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["parse_time"]
 
 [[bin]]
 name = "sleep"
diff --git a/src/sort/Cargo.toml b/src/sort/Cargo.toml
index cb5985b76..fbf6870fc 100644
--- a/src/sort/Cargo.toml
+++ b/src/sort/Cargo.toml
@@ -12,7 +12,10 @@ path = "sort.rs"
 getopts = "0.2.14"
 semver = "0.7.0"
 itertools = "0.6.0"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [[bin]]
 name = "sort"
diff --git a/src/stat/Cargo.toml b/src/stat/Cargo.toml
index 49c0cb641..bf66d2779 100644
--- a/src/stat/Cargo.toml
+++ b/src/stat/Cargo.toml
@@ -14,7 +14,6 @@ time = "0.1.38"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["entries"]
 
 [[bin]]
diff --git a/src/sync/Cargo.toml b/src/sync/Cargo.toml
index 22fcc2f82..b82b55999 100644
--- a/src/sync/Cargo.toml
+++ b/src/sync/Cargo.toml
@@ -13,7 +13,10 @@ getopts = "0.2.14"
 libc = "0.2.26"
 winapi = { version = "0.3", features = ["handleapi", "winerror"] }
 kernel32-sys = "0.2.2"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["wide"]
 
 [[bin]]
 name = "sync"
diff --git a/src/timeout/Cargo.toml b/src/timeout/Cargo.toml
index ae28ccc59..75ce9a289 100644
--- a/src/timeout/Cargo.toml
+++ b/src/timeout/Cargo.toml
@@ -12,7 +12,10 @@ path = "timeout.rs"
 getopts = "0.2.14"
 libc = "0.2.26"
 time = "0.1.38"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["parse_time", "process"]
 
 [[bin]]
 name = "timeout"
diff --git a/src/touch/Cargo.toml b/src/touch/Cargo.toml
index c7b8e4a26..90dcae2b3 100644
--- a/src/touch/Cargo.toml
+++ b/src/touch/Cargo.toml
@@ -15,7 +15,6 @@ time = "0.1.38"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["libc"]
 
 [[bin]]
diff --git a/src/tr/Cargo.toml b/src/tr/Cargo.toml
index 054fece62..2027fab87 100644
--- a/src/tr/Cargo.toml
+++ b/src/tr/Cargo.toml
@@ -12,10 +12,7 @@ path = "tr.rs"
 getopts = "0.2.14"
 bit-set = "0.4.0"
 fnv = "1.0.5"
-
-[dependencies.uucore]
-path = "../uucore"
-default-features = false
+uucore = { path = "../uucore" }
 
 [[bin]]
 name = "tr"
diff --git a/src/tty/Cargo.toml b/src/tty/Cargo.toml
index 6fd2abd24..be18d0488 100644
--- a/src/tty/Cargo.toml
+++ b/src/tty/Cargo.toml
@@ -11,7 +11,10 @@ path = "tty.rs"
 [dependencies]
 getopts = "0.2.14"
 libc = "0.2.26"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["fs"]
 
 [[bin]]
 name = "tty"
diff --git a/src/uname/Cargo.toml b/src/uname/Cargo.toml
index c9cef3767..6498ad7bf 100644
--- a/src/uname/Cargo.toml
+++ b/src/uname/Cargo.toml
@@ -11,10 +11,7 @@ path = "uname.rs"
 [dependencies]
 clap = "2.20.0"
 platform-info = { git = "https://github.com/uutils/platform-info" }
-
-[dependencies.uucore]
-path = "../uucore"
-default-features = false
+uucore = { path = "../uucore" }
 
 [[bin]]
 name = "uname"
diff --git a/src/unexpand/Cargo.toml b/src/unexpand/Cargo.toml
index 49bca8ba3..85d7d15b9 100644
--- a/src/unexpand/Cargo.toml
+++ b/src/unexpand/Cargo.toml
@@ -11,7 +11,10 @@ path = "unexpand.rs"
 [dependencies]
 getopts = "0.2.14"
 unicode-width = "0.1.4"
-uucore = { path="../uucore" }
+
+[dependencies.uucore]
+path = "../uucore"
+features = ["utf8"]
 
 [[bin]]
 name = "unexpand"
diff --git a/src/uniq/Cargo.toml b/src/uniq/Cargo.toml
index 0ef73fc66..27ba4b672 100644
--- a/src/uniq/Cargo.toml
+++ b/src/uniq/Cargo.toml
@@ -10,10 +10,7 @@ path = "uniq.rs"
 
 [dependencies]
 getopts = "0.2.14"
-
-[dependencies.uucore]
-path="../uucore"
-default-features = false
+uucore = { path = "../uucore" }
 
 [[bin]]
 name = "uniq"
diff --git a/src/uptime/Cargo.toml b/src/uptime/Cargo.toml
index 275050bbc..cb01f2b31 100644
--- a/src/uptime/Cargo.toml
+++ b/src/uptime/Cargo.toml
@@ -13,7 +13,6 @@ getopts = "0.2.14"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["utmpx"]
 
 [[bin]]
diff --git a/src/users/Cargo.toml b/src/users/Cargo.toml
index 007d23973..9513035c8 100644
--- a/src/users/Cargo.toml
+++ b/src/users/Cargo.toml
@@ -12,7 +12,6 @@ path = "users.rs"
 getopts = "0.2.14"
 
 [dependencies.uucore]
-default-features = false
 features = ["utmpx"]
 path = "../uucore"
 
diff --git a/src/uucore/Cargo.toml b/src/uucore/Cargo.toml
index e1e56fed3..d18f834b3 100644
--- a/src/uucore/Cargo.toml
+++ b/src/uucore/Cargo.toml
@@ -20,7 +20,7 @@ process = ["libc"]
 signals = []
 entries = ["libc"]
 wide = []
-default = ["fs", "libc", "utf8", "encoding", "parse_time", "mode", "utmpx", "process", "entries", "signals", "wide"]
+default = []
 
 [lib]
 path = "lib.rs"
diff --git a/src/who/Cargo.toml b/src/who/Cargo.toml
index 2275d67e2..51781a29f 100644
--- a/src/who/Cargo.toml
+++ b/src/who/Cargo.toml
@@ -10,7 +10,6 @@ path = "who.rs"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
 features = ["utmpx"]
 
 [dependencies.clippy]
diff --git a/src/whoami/Cargo.toml b/src/whoami/Cargo.toml
index 932df68ba..835e8569b 100644
--- a/src/whoami/Cargo.toml
+++ b/src/whoami/Cargo.toml
@@ -2,6 +2,7 @@
 name = "whoami"
 version = "0.0.1"
 authors = []
+description = "Print effective user ID."
 build = "../../mkmain.rs"
 
 [lib]
@@ -9,14 +10,13 @@ name = "uu_whoami"
 path = "whoami.rs"
 
 [dependencies]
-getopts = "0.2.14"
+clap = "2.31"
 winapi = { version = "0.3", features = ["lmcons"] }
 advapi32-sys = "0.2.0"
 
 [dependencies.uucore]
 path = "../uucore"
-default-features = false
-features = ["entries"]
+features = ["entries", "wide"]
 
 [[bin]]
 name = "whoami"
diff --git a/src/whoami/whoami.rs b/src/whoami/whoami.rs
index 13bcc586a..097812706 100644
--- a/src/whoami/whoami.rs
+++ b/src/whoami/whoami.rs
@@ -11,45 +11,34 @@
 
 /* last synced with: whoami (GNU coreutils) 8.21 */
 
-extern crate getopts;
-
+#[macro_use]
+extern crate clap;
 #[macro_use]
 extern crate uucore;
 
-use getopts::Options;
-
 mod platform;
 
-static NAME: &'static str = "whoami";
-static VERSION: &'static str = env!("CARGO_PKG_VERSION");
+// force a re-build whenever Cargo.toml changes
+const _CARGO_TOML: &'static str = include_str!("Cargo.toml");
 
 pub fn uumain(args: Vec<String>) -> i32 {
-    let mut opts = Options::new();
+    let app = app_from_crate!();
 
-    opts.optflag("h", "help", "display this help and exit");
-    opts.optflag("V", "version", "output version information and exit");
+    if let Err(err) = app.get_matches_from_safe(args) {
+        if err.kind == clap::ErrorKind::HelpDisplayed
+            || err.kind == clap::ErrorKind::VersionDisplayed
+        {
+            println!("{}", err);
+            0
+        } else {
+            show_error!("{}", err);
+            1
+        }
+    } else {
+        exec();
 
-    let matches = match opts.parse(&args[1..]) {
-        Ok(m) => m,
-        Err(f) => crash!(1, "{}", f),
-    };
-    if matches.opt_present("help") {
-        println!("{} {}", NAME, VERSION);
-        println!("");
-        println!("Usage:");
-        println!("  {} [OPTIONS]", NAME);
-        println!("");
-        println!("{}", opts.usage("print effective userid"));
-        return 0;
+        0
     }
-    if matches.opt_present("version") {
-        println!("{} {}", NAME, VERSION);
-        return 0;
-    }
-
-    exec();
-
-    0
 }
 
 pub fn exec() {
diff --git a/src/yes/Cargo.toml b/src/yes/Cargo.toml
index ae5bf20f6..5c98a3e65 100644
--- a/src/yes/Cargo.toml
+++ b/src/yes/Cargo.toml
@@ -2,6 +2,7 @@
 name = "yes"
 version = "0.0.1"
 authors = []
+description = "Repeatedly output a line with all specified STRING(s), or 'y'."
 build = "../../mkmain.rs"
 
 [lib]
@@ -9,8 +10,8 @@ name = "uu_yes"
 path = "yes.rs"
 
 [dependencies]
-getopts = "0.2.14"
-uucore = { path="../uucore" }
+clap = "2.31"
+uucore = { path = "../uucore" }
 
 [[bin]]
 name = "yes"
diff --git a/src/yes/yes.rs b/src/yes/yes.rs
index 99b4efb81..35398ffa8 100644
--- a/src/yes/yes.rs
+++ b/src/yes/yes.rs
@@ -11,63 +11,69 @@
 
 /* last synced with: yes (GNU coreutils) 8.13 */
 
-extern crate getopts;
-
+#[macro_use]
+extern crate clap;
 #[macro_use]
 extern crate uucore;
 
-use getopts::Options;
+use clap::Arg;
+use std::borrow::Cow;
+use std::io::{self, Write};
 
-static NAME: &'static str = "yes";
-static VERSION: &'static str = env!("CARGO_PKG_VERSION");
+// force a re-build whenever Cargo.toml changes
+const _CARGO_TOML: &'static str = include_str!("Cargo.toml");
 
 const BUF_SIZE: usize = 8192;
 
 pub fn uumain(args: Vec<String>) -> i32 {
-    let mut opts = Options::new();
+    let app = app_from_crate!().arg(Arg::with_name("STRING").index(1).multiple(true));
 
-    opts.optflag("h", "help", "display this help and exit");
-    opts.optflag("V", "version", "output version information and exit");
-
-    let matches = match opts.parse(&args[1..]) {
+    let matches = match app.get_matches_from_safe(args) {
         Ok(m) => m,
-        Err(f) => crash!(1, "invalid options\n{}", f),
+        Err(ref e)
+            if e.kind == clap::ErrorKind::HelpDisplayed
+                || e.kind == clap::ErrorKind::VersionDisplayed =>
+        {
+            println!("{}", e);
+            return 0;
+        }
+        Err(f) => {
+            show_error!("{}", f);
+            return 1;
+        }
     };
-    if matches.opt_present("help") {
-        println!("{} {}", NAME, VERSION);
-        println!("");
-        println!("Usage:");
-        println!("  {0} [STRING]... [OPTION]...", NAME);
-        println!("");
-        print!(
-            "{}",
-            opts.usage("Repeatedly output a line with all specified STRING(s), or 'y'.")
-        );
-        return 0;
-    }
-    if matches.opt_present("version") {
-        println!("{} {}", NAME, VERSION);
-        return 0;
-    }
-    let string = if matches.free.is_empty() {
-        "y".to_owned()
+
+    let string = if let Some(values) = matches.values_of("STRING") {
+        let mut result = values.fold(String::new(), |res, s| res + s + " ");
+        result.pop();
+        result.push('\n');
+        Cow::from(result)
     } else {
-        matches.free.join(" ")
+        Cow::from("y\n")
     };
 
-    let mut multistring = string.clone();
-    while multistring.len() < BUF_SIZE - string.len() - 1 {
-        multistring.push_str("\n");
-        multistring.push_str(&string);
-    }
+    let mut buffer = [0; BUF_SIZE];
+    let bytes = if string.len() < BUF_SIZE / 2 {
+        let mut size = 0;
+        while size < BUF_SIZE - string.len() {
+            let (_, right) = buffer.split_at_mut(size);
+            right[..string.len()].copy_from_slice(string.as_bytes());
+            size += string.len();
+        }
+        &buffer[..size]
+    } else {
+        string.as_bytes()
+    };
 
-    exec(&multistring[..]);
+    exec(bytes);
 
     0
 }
 
-pub fn exec(string: &str) {
+pub fn exec(bytes: &[u8]) {
+    let stdout_raw = io::stdout();
+    let mut stdout = stdout_raw.lock();
     loop {
-        println!("{}", string)
+        stdout.write_all(bytes).unwrap();
     }
 }