env: support string args by "-S", "-vS" or "--split-strings"

.vscode/cspell.dictionaries/shell.wordlist.txt

@@ -25,6 +25,7 @@ sudoedit
 tcsh
 tzselect
 urandom
+VARNAME
 wtmp
 zsh
 

Cargo.lock

@@ -547,7 +547,7 @@ dependencies = [
  "lazy_static",
  "proc-macro2",
  "regex",
- "syn 2.0.23",
+ "syn 2.0.32",
  "unicode-xid",
 ]
 
@@ -559,7 +559,7 @@ checksum = "3e1a2532e4ed4ea13031c13bc7bc0dbca4aae32df48e9d77f0d1e743179f2ea1"
 dependencies = [
  "lazy_static",
  "proc-macro2",
- "syn 2.0.23",
+ "syn 2.0.32",
 ]
 
 [[package]]
@@ -574,7 +574,7 @@ dependencies = [
  "lazy_static",
  "proc-macro2",
  "quote",
- "syn 2.0.23",
+ "syn 2.0.32",
 ]
 
 [[package]]
@@ -942,7 +942,7 @@ checksum = "89ca545a94061b6365f2c7355b4b32bd20df3ff95f02da9329b34ccc3bd6ee72"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.23",
+ "syn 2.0.32",
 ]
 
 [[package]]
@@ -1791,7 +1791,7 @@ dependencies = [
  "regex",
  "relative-path",
  "rustc_version",
- "syn 2.0.23",
+ "syn 2.0.32",
  "unicode-ident",
 ]
 
@@ -1902,9 +1902,23 @@ checksum = "e25dfac463d778e353db5be2449d1cce89bd6fd23c9f1ea21310ce6e5a1b29c4"
 
 [[package]]
 name = "serde"
-version = "1.0.147"
+version = "1.0.193"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d193d69bae983fc11a79df82342761dfbf28a99fc8d203dca4c3c1b590948965"
+checksum = "25dd9975e68d0cb5aa1120c288333fc98731bd1dd12f561e468ea4728c042b89"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.193"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43576ca501357b9b071ac53cdc7da8ef0cbd9493d8df094cd821777ea6e894d3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.32",
+]
 
 [[package]]
 name = "sha1"
@@ -2039,9 +2053,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.23"
+version = "2.0.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "59fb7d6d8281a51045d62b8eb3a7d1ce347b76f312af50cd3dc0af39c87c1737"
+checksum = "239814284fd6f1a4ffe4ca893952cdd93c224b6a1571c9a9eadd670295c0c9e2"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3296,7 +3310,7 @@ dependencies = [
  "once_cell",
  "proc-macro2",
  "quote",
- "syn 2.0.23",
+ "syn 2.0.32",
  "wasm-bindgen-shared",
 ]
 
@@ -3318,7 +3332,7 @@ checksum = "54681b18a46765f095758388f2d0cf16eb8d4169b639ab575a8f5693af210c7b"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.23",
+ "syn 2.0.32",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]

src/uu/env/src/env.rs

@@ -5,18 +5,32 @@
 
 // spell-checker:ignore (ToDO) chdir execvp progname subcommand subcommands unsets setenv putenv spawnp SIGSEGV SIGBUS sigaction
 
+pub mod native_int_str;
+pub mod parse_error;
+pub mod split_iterator;
+pub mod string_expander;
+pub mod string_parser;
+pub mod variable_parser;
+
+use clap::builder::ValueParser;
 use clap::{crate_name, crate_version, Arg, ArgAction, Command};
 use ini::Ini;
+use native_int_str::{
+    from_native_int_representation_owned, Convert, NCvt, NativeIntStr, NativeIntString, NativeStr,
+};
 #[cfg(unix)]
 use nix::sys::signal::{raise, sigaction, SaFlags, SigAction, SigHandler, SigSet, Signal};
 use std::borrow::Cow;
 use std::env;
+use std::ffi::{OsStr, OsString};
 use std::io::{self, Write};
+use std::ops::Deref;
+
 #[cfg(unix)]
 use std::os::unix::process::ExitStatusExt;
-use std::process;
+use std::process::{self};
 use uucore::display::Quotable;
-use uucore::error::{UClapError, UResult, USimpleError, UUsageError};
+use uucore::error::{ExitCode, UError, UResult, USimpleError, UUsageError};
 use uucore::line_ending::LineEnding;
 use uucore::{format_usage, help_about, help_section, help_usage, show_warning};
 
@@ -24,14 +38,16 @@ const ABOUT: &str = help_about!("env.md");
 const USAGE: &str = help_usage!("env.md");
 const AFTER_HELP: &str = help_section!("after help", "env.md");
 
+const ERROR_MSG_S_SHEBANG: &str = "use -[v]S to pass options in shebang lines";
+
 struct Options<'a> {
     ignore_env: bool,
     line_ending: LineEnding,
-    running_directory: Option<&'a str>,
+    running_directory: Option<&'a OsStr>,
-    files: Vec<&'a str>,
+    files: Vec<&'a OsStr>,
-    unsets: Vec<&'a str>,
+    unsets: Vec<&'a OsStr>,
-    sets: Vec<(&'a str, &'a str)>,
+    sets: Vec<(Cow<'a, OsStr>, Cow<'a, OsStr>)>,
-    program: Vec<&'a str>,
+    program: Vec<&'a OsStr>,
 }
 
 // print name=value env pairs on screen
@@ -44,13 +60,13 @@ fn print_env(line_ending: LineEnding) {
     }
 }
 
-fn parse_name_value_opt<'a>(opts: &mut Options<'a>, opt: &'a str) -> UResult<bool> {
+fn parse_name_value_opt<'a>(opts: &mut Options<'a>, opt: &'a OsStr) -> UResult<bool> {
     // is it a NAME=VALUE like opt ?
-    if let Some(idx) = opt.find('=') {
+    let wrap = NativeStr::<'a>::new(opt);
+    let split_o = wrap.split_once(&'=');
+    if let Some((name, value)) = split_o {
         // yes, so push name, value pair
-        let (name, value) = opt.split_at(idx);
+        opts.sets.push((name, value));
-        opts.sets.push((name, &value['='.len_utf8()..]));
-
         Ok(false)
     } else {
         // no, it's a program-like opt
@@ -58,7 +74,7 @@ fn parse_name_value_opt<'a>(opts: &mut Options<'a>, opt: &'a str) -> UResult<boo
     }
 }
 
-fn parse_program_opt<'a>(opts: &mut Options<'a>, opt: &'a str) -> UResult<()> {
+fn parse_program_opt<'a>(opts: &mut Options<'a>, opt: &'a OsStr) -> UResult<()> {
     if opts.line_ending == LineEnding::Nul {
         Err(UUsageError::new(
             125,
@@ -96,23 +112,6 @@ fn load_config_file(opts: &mut Options) -> UResult<()> {
     Ok(())
 }
 
-#[cfg(not(windows))]
-#[allow(clippy::ptr_arg)]
-fn build_command<'a, 'b>(args: &'a Vec<&'b str>) -> (Cow<'b, str>, &'a [&'b str]) {
-    let progname = Cow::from(args[0]);
-    (progname, &args[1..])
-}
-
-#[cfg(windows)]
-fn build_command<'a, 'b>(args: &'a mut Vec<&'b str>) -> (Cow<'b, str>, &'a [&'b str]) {
-    args.insert(0, "/d/c");
-    let progname = env::var("ComSpec")
-        .map(Cow::from)
-        .unwrap_or_else(|_| Cow::from("cmd"));
-
-    (progname, &args[..])
-}
-
 pub fn uu_app() -> Command {
     Command::new(crate_name!())
         .version(crate_version!())
@@ -134,6 +133,7 @@ pub fn uu_app() -> Command {
                 .long("chdir")
                 .number_of_values(1)
                 .value_name("DIR")
+                .value_parser(ValueParser::os_string())
                 .value_hint(clap::ValueHint::DirPath)
                 .help("change working directory to DIR"),
         )
@@ -153,6 +153,7 @@ pub fn uu_app() -> Command {
                 .long("file")
                 .value_name("PATH")
                 .value_hint(clap::ValueHint::FilePath)
+                .value_parser(ValueParser::os_string())
                 .action(ArgAction::Append)
                 .help(
                     "read and set variables from a \".env\"-style configuration file \
@@ -165,25 +166,172 @@ pub fn uu_app() -> Command {
                 .long("unset")
                 .value_name("NAME")
                 .action(ArgAction::Append)
+                .value_parser(ValueParser::os_string())
                 .help("remove variable from the environment"),
         )
-        .arg(Arg::new("vars").action(ArgAction::Append))
+        .arg(
+            Arg::new("debug")
+                .short('v')
+                .long("debug")
+                .action(ArgAction::SetTrue)
+                .help("print verbose information for each processing step"),
+        )
+        .arg(
+            Arg::new("split-string") // split string handling is implemented directly, not using CLAP. But this entry here is needed for the help information output.
+                .short('S')
+                .long("split-string")
+                .value_name("S")
+                .action(ArgAction::Set)
+                .value_parser(ValueParser::os_string())
+                .help("process and split S into separate arguments; used to pass multiple arguments on shebang lines")
+        )
+        .arg(
+            Arg::new("vars")
+                .action(ArgAction::Append)
+                .value_parser(ValueParser::os_string())
+        )
+}
+
+pub fn parse_args_from_str(text: &NativeIntStr) -> UResult<Vec<NativeIntString>> {
+    split_iterator::split(text).map_err(|e| match e {
+        parse_error::ParseError::BackslashCNotAllowedInDoubleQuotes { pos: _ } => {
+            USimpleError::new(125, "'\\c' must not appear in double-quoted -S string")
+        }
+        parse_error::ParseError::InvalidBackslashAtEndOfStringInMinusS { pos: _, quoting: _ } => {
+            USimpleError::new(125, "invalid backslash at end of string in -S")
+        }
+        parse_error::ParseError::InvalidSequenceBackslashXInMinusS { pos: _, c } => {
+            USimpleError::new(125, format!("invalid sequence '\\{}' in -S", c))
+        }
+        parse_error::ParseError::MissingClosingQuote { pos: _, c: _ } => {
+            USimpleError::new(125, "no terminating quote in -S string")
+        }
+        parse_error::ParseError::ParsingOfVariableNameFailed { pos, msg } => {
+            USimpleError::new(125, format!("variable name issue (at {}): {}", pos, msg,))
+        }
+        _ => USimpleError::new(125, format!("Error: {:?}", e)),
+    })
+}
+
+fn debug_print_args(args: &[OsString]) {
+    eprintln!("input args:");
+    for (i, arg) in args.iter().enumerate() {
+        eprintln!("arg[{}]: {}", i, arg.quote());
+    }
+}
+
+fn check_and_handle_string_args(
+    arg: &OsString,
+    prefix_to_test: &str,
+    all_args: &mut Vec<std::ffi::OsString>,
+    do_debug_print_args: Option<&Vec<OsString>>,
+) -> UResult<bool> {
+    let native_arg = NCvt::convert(arg);
+    if let Some(remaining_arg) = native_arg.strip_prefix(&*NCvt::convert(prefix_to_test)) {
+        if let Some(input_args) = do_debug_print_args {
+            debug_print_args(input_args); // do it here, such that its also printed when we get an error/panic during parsing
+        }
+
+        let arg_strings = parse_args_from_str(remaining_arg)?;
+        all_args.extend(
+            arg_strings
+                .into_iter()
+                .map(from_native_int_representation_owned),
+        );
+
+        Ok(true)
+    } else {
+        Ok(false)
+    }
+}
+
+#[derive(Default)]
+struct EnvAppData {
+    do_debug_printing: bool,
+    had_string_argument: bool,
+}
+
+impl EnvAppData {
+    fn make_error_no_such_file_or_dir(&self, prog: &OsStr) -> Box<dyn UError> {
+        uucore::show_error!("{}: No such file or directory", prog.quote());
+        if !self.had_string_argument {
+            uucore::show_error!("{}", ERROR_MSG_S_SHEBANG);
+        }
+        ExitCode::new(127)
+    }
+
+    fn process_all_string_arguments(
+        &mut self,
+        original_args: &Vec<OsString>,
+    ) -> UResult<Vec<std::ffi::OsString>> {
+        let mut all_args: Vec<std::ffi::OsString> = Vec::new();
+        for arg in original_args {
+            match arg {
+                b if check_and_handle_string_args(b, "--split-string", &mut all_args, None)? => {
+                    self.had_string_argument = true;
+                }
+                b if check_and_handle_string_args(b, "-S", &mut all_args, None)? => {
+                    self.had_string_argument = true;
+                }
+                b if check_and_handle_string_args(
+                    b,
+                    "-vS",
+                    &mut all_args,
+                    Some(original_args),
+                )? =>
+                {
+                    self.do_debug_printing = true;
+                    self.had_string_argument = true;
+                }
+                _ => {
+                    all_args.push(arg.clone());
+                }
+            }
+        }
+
+        Ok(all_args)
     }
 
     #[allow(clippy::cognitive_complexity)]
-fn run_env(args: impl uucore::Args) -> UResult<()> {
+    fn run_env(&mut self, original_args: impl uucore::Args) -> UResult<()> {
+        let original_args: Vec<OsString> = original_args.collect();
+        let args = self.process_all_string_arguments(&original_args)?;
+
         let app = uu_app();
-    let matches = app.try_get_matches_from(args).with_exit_code(125)?;
+        let matches = app
+            .try_get_matches_from(args)
+            .map_err(|e| -> Box<dyn UError> {
+                match e.kind() {
+                    clap::error::ErrorKind::DisplayHelp
+                    | clap::error::ErrorKind::DisplayVersion => e.into(),
+                    _ => {
+                        // extent any real issue with parameter parsing by the ERROR_MSG_S_SHEBANG
+                        let s = format!("{}", e);
+                        if !s.is_empty() {
+                            let s = s.trim_end();
+                            uucore::show_error!("{}", s);
+                        }
+                        uucore::show_error!("{}", ERROR_MSG_S_SHEBANG);
+                        uucore::error::ExitCode::new(125)
+                    }
+                }
+            })?;
+
+        let did_debug_printing_before = self.do_debug_printing; // could have been done already as part of the "-vS" string parsing
+        let do_debug_printing = self.do_debug_printing || matches.get_flag("debug");
+        if do_debug_printing && !did_debug_printing_before {
+            debug_print_args(&original_args);
+        }
 
         let ignore_env = matches.get_flag("ignore-environment");
         let line_ending = LineEnding::from_zero_flag(matches.get_flag("null"));
-    let running_directory = matches.get_one::<String>("chdir").map(|s| s.as_str());
+        let running_directory = matches.get_one::<OsString>("chdir").map(|s| s.as_os_str());
-    let files = match matches.get_many::<String>("file") {
+        let files = match matches.get_many::<OsString>("file") {
-        Some(v) => v.map(|s| s.as_str()).collect(),
+            Some(v) => v.map(|s| s.as_os_str()).collect(),
             None => Vec::with_capacity(0),
         };
-    let unsets = match matches.get_many::<String>("unset") {
+        let unsets = match matches.get_many::<OsString>("unset") {
-        Some(v) => v.map(|s| s.as_str()).collect(),
+            Some(v) => v.map(|s| s.as_os_str()).collect(),
             None => Vec::with_capacity(0),
         };
 
@@ -204,14 +352,14 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
                 Err(error) => {
                     return Err(USimpleError::new(
                         125,
-                    format!("cannot change directory to \"{d}\": {error}"),
+                        format!("cannot change directory to {}: {error}", d.quote()),
                     ));
                 }
             };
         }
 
         let mut begin_prog_opts = false;
-    if let Some(mut iter) = matches.get_many::<String>("vars") {
+        if let Some(mut iter) = matches.get_many::<OsString>("vars") {
             // read NAME=VALUE arguments (and up to a single program argument)
             while !begin_prog_opts {
                 if let Some(opt) = iter.next() {
@@ -244,7 +392,7 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
 
         // remove all env vars if told to ignore presets
         if opts.ignore_env {
-        for (ref name, _) in env::vars() {
+            for (ref name, _) in env::vars_os() {
                 env::remove_var(name);
             }
         }
@@ -254,7 +402,11 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
 
         // unset specified env vars
         for name in &opts.unsets {
-        if name.is_empty() || name.contains(0 as char) || name.contains('=') {
+            let native_name = NativeStr::new(name);
+            if name.is_empty()
+                || native_name.contains(&'\0').unwrap()
+                || native_name.contains(&'=').unwrap()
+            {
                 return Err(USimpleError::new(
                     125,
                     format!("cannot unset {}: Invalid argument", name.quote()),
@@ -265,7 +417,7 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
         }
 
         // set specified env vars
-    for &(name, val) in &opts.sets {
+        for (name, val) in &opts.sets {
             /*
              * set_var panics if name is an empty string
              * set_var internally calls setenv (on unix at least), while GNU env calls putenv instead.
@@ -300,10 +452,15 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
             print_env(opts.line_ending);
         } else {
             // we need to execute a command
-        #[cfg(windows)]
+            let prog = Cow::from(opts.program[0]);
-        let (prog, args) = build_command(&mut opts.program);
+            let args = &opts.program[1..];
-        #[cfg(not(windows))]
+
-        let (prog, args) = build_command(&opts.program);
+            if do_debug_printing {
+                eprintln!("executable: {}", prog.quote());
+                for (i, arg) in args.iter().enumerate() {
+                    eprintln!("arg[{}]: {}", i, arg.quote());
+                }
+            }
 
             /*
              * On Unix-like systems Command::status either ends up calling either fork or posix_spawnp
@@ -333,7 +490,11 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
                         let _ = unsafe {
                             sigaction(
                                 signal,
-                            &SigAction::new(SigHandler::SigDfl, SaFlags::empty(), SigSet::all()),
+                                &SigAction::new(
+                                    SigHandler::SigDfl,
+                                    SaFlags::empty(),
+                                    SigSet::all(),
+                                ),
                             )
                         };
 
@@ -342,16 +503,25 @@ fn run_env(args: impl uucore::Args) -> UResult<()> {
                     #[cfg(not(unix))]
                     return Err(exit.code().unwrap().into());
                 }
-            Err(ref err) if err.kind() == io::ErrorKind::NotFound => return Err(127.into()),
+                Err(ref err)
-            Err(_) => return Err(126.into()),
+                    if (err.kind() == io::ErrorKind::NotFound)
+                        || (err.kind() == io::ErrorKind::InvalidInput) =>
+                {
+                    return Err(self.make_error_no_such_file_or_dir(prog.deref()));
+                }
+                Err(e) => {
+                    uucore::show_error!("unknown error: {:?}", e);
+                    return Err(126.into());
+                }
                 Ok(_) => (),
             }
         }
 
         Ok(())
     }
+}
 
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
-    run_env(args)
+    EnvAppData::default().run_env(args)
 }

src/uu/env/src/native_int_str.rs

@@ -0,0 +1,325 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+// This module contains classes and functions for dealing with the differences
+// between operating systems regarding the lossless processing of OsStr/OsString.
+// In contrast to existing crates with similar purpose, this module does not use any
+// `unsafe` features or functions.
+// Due to a suboptimal design aspect of OsStr/OsString on windows, we need to
+// encode/decode to wide chars on windows operating system.
+// This prevents borrowing from OsStr on windows. Anyway, if optimally used,#
+// this conversion needs to be done only once in the beginning and at the end.
+
+use std::ffi::OsString;
+#[cfg(not(target_os = "windows"))]
+use std::os::unix::ffi::{OsStrExt, OsStringExt};
+#[cfg(target_os = "windows")]
+use std::os::windows::prelude::*;
+use std::{borrow::Cow, ffi::OsStr};
+
+#[cfg(target_os = "windows")]
+use u16 as NativeIntCharU;
+#[cfg(not(target_os = "windows"))]
+use u8 as NativeIntCharU;
+
+pub type NativeCharInt = NativeIntCharU;
+pub type NativeIntStr = [NativeCharInt];
+pub type NativeIntString = Vec<NativeCharInt>;
+
+pub struct NCvt;
+
+pub trait Convert<From, To> {
+    fn convert(f: From) -> To;
+}
+
+// ================ str/String =================
+
+impl<'a> Convert<&'a str, Cow<'a, NativeIntStr>> for NCvt {
+    fn convert(f: &'a str) -> Cow<'a, NativeIntStr> {
+        #[cfg(target_os = "windows")]
+        {
+            Cow::Owned(f.encode_utf16().collect())
+        }
+
+        #[cfg(not(target_os = "windows"))]
+        {
+            Cow::Borrowed(f.as_bytes())
+        }
+    }
+}
+
+impl<'a> Convert<&'a String, Cow<'a, NativeIntStr>> for NCvt {
+    fn convert(f: &'a String) -> Cow<'a, NativeIntStr> {
+        #[cfg(target_os = "windows")]
+        {
+            Cow::Owned(f.encode_utf16().collect())
+        }
+
+        #[cfg(not(target_os = "windows"))]
+        {
+            Cow::Borrowed(f.as_bytes())
+        }
+    }
+}
+
+impl<'a> Convert<String, Cow<'a, NativeIntStr>> for NCvt {
+    fn convert(f: String) -> Cow<'a, NativeIntStr> {
+        #[cfg(target_os = "windows")]
+        {
+            Cow::Owned(f.encode_utf16().collect())
+        }
+
+        #[cfg(not(target_os = "windows"))]
+        {
+            Cow::Owned(f.into_bytes())
+        }
+    }
+}
+
+// ================ OsStr/OsString =================
+
+impl<'a> Convert<&'a OsStr, Cow<'a, NativeIntStr>> for NCvt {
+    fn convert(f: &'a OsStr) -> Cow<'a, NativeIntStr> {
+        to_native_int_representation(f)
+    }
+}
+
+impl<'a> Convert<&'a OsString, Cow<'a, NativeIntStr>> for NCvt {
+    fn convert(f: &'a OsString) -> Cow<'a, NativeIntStr> {
+        to_native_int_representation(f)
+    }
+}
+
+impl<'a> Convert<OsString, Cow<'a, NativeIntStr>> for NCvt {
+    fn convert(f: OsString) -> Cow<'a, NativeIntStr> {
+        #[cfg(target_os = "windows")]
+        {
+            Cow::Owned(f.encode_wide().collect())
+        }
+
+        #[cfg(not(target_os = "windows"))]
+        {
+            Cow::Owned(f.into_vec())
+        }
+    }
+}
+
+// ================ Vec<Str/String> =================
+
+impl<'a> Convert<&'a Vec<&'a str>, Vec<Cow<'a, NativeIntStr>>> for NCvt {
+    fn convert(f: &'a Vec<&'a str>) -> Vec<Cow<'a, NativeIntStr>> {
+        f.iter().map(|x| Self::convert(*x)).collect()
+    }
+}
+
+impl<'a> Convert<Vec<&'a str>, Vec<Cow<'a, NativeIntStr>>> for NCvt {
+    fn convert(f: Vec<&'a str>) -> Vec<Cow<'a, NativeIntStr>> {
+        f.iter().map(|x| Self::convert(*x)).collect()
+    }
+}
+
+impl<'a> Convert<&'a Vec<String>, Vec<Cow<'a, NativeIntStr>>> for NCvt {
+    fn convert(f: &'a Vec<String>) -> Vec<Cow<'a, NativeIntStr>> {
+        f.iter().map(Self::convert).collect()
+    }
+}
+
+impl<'a> Convert<Vec<String>, Vec<Cow<'a, NativeIntStr>>> for NCvt {
+    fn convert(f: Vec<String>) -> Vec<Cow<'a, NativeIntStr>> {
+        f.into_iter().map(Self::convert).collect()
+    }
+}
+
+pub fn to_native_int_representation(input: &OsStr) -> Cow<'_, NativeIntStr> {
+    #[cfg(target_os = "windows")]
+    {
+        Cow::Owned(input.encode_wide().collect())
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    {
+        Cow::Borrowed(input.as_bytes())
+    }
+}
+
+#[allow(clippy::needless_pass_by_value)] // needed on windows
+pub fn from_native_int_representation(input: Cow<'_, NativeIntStr>) -> Cow<'_, OsStr> {
+    #[cfg(target_os = "windows")]
+    {
+        Cow::Owned(OsString::from_wide(&input))
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    {
+        match input {
+            Cow::Borrowed(borrow) => Cow::Borrowed(OsStr::from_bytes(borrow)),
+            Cow::Owned(own) => Cow::Owned(OsString::from_vec(own)),
+        }
+    }
+}
+
+#[allow(clippy::needless_pass_by_value)] // needed on windows
+pub fn from_native_int_representation_owned(input: NativeIntString) -> OsString {
+    #[cfg(target_os = "windows")]
+    {
+        OsString::from_wide(&input)
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    {
+        OsString::from_vec(input)
+    }
+}
+
+pub fn get_single_native_int_value(c: &char) -> Option<NativeCharInt> {
+    #[cfg(target_os = "windows")]
+    {
+        let mut buf = [0u16, 0];
+        let s = c.encode_utf16(&mut buf);
+        if s.len() == 1 {
+            Some(buf[0])
+        } else {
+            None
+        }
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    {
+        let mut buf = [0u8, 0, 0, 0];
+        let s = c.encode_utf8(&mut buf);
+        if s.len() == 1 {
+            Some(buf[0])
+        } else {
+            None
+        }
+    }
+}
+
+pub fn get_char_from_native_int(ni: NativeCharInt) -> Option<(char, NativeCharInt)> {
+    let c_opt;
+    #[cfg(target_os = "windows")]
+    {
+        c_opt = char::decode_utf16([ni; 1]).next().unwrap().ok();
+    };
+
+    #[cfg(not(target_os = "windows"))]
+    {
+        c_opt = std::str::from_utf8(&[ni; 1])
+            .ok()
+            .map(|x| x.chars().next().unwrap());
+    };
+
+    if let Some(c) = c_opt {
+        return Some((c, ni));
+    }
+
+    None
+}
+
+pub struct NativeStr<'a> {
+    native: Cow<'a, NativeIntStr>,
+}
+
+impl<'a> NativeStr<'a> {
+    pub fn new(str: &'a OsStr) -> Self {
+        Self {
+            native: to_native_int_representation(str),
+        }
+    }
+
+    pub fn native(&self) -> Cow<'a, NativeIntStr> {
+        self.native.clone()
+    }
+
+    pub fn into_native(self) -> Cow<'a, NativeIntStr> {
+        self.native
+    }
+
+    pub fn contains(&self, x: &char) -> Option<bool> {
+        let n_c = get_single_native_int_value(x)?;
+        Some(self.native.contains(&n_c))
+    }
+
+    pub fn slice(&self, from: usize, to: usize) -> Cow<'a, OsStr> {
+        let result = self.match_cow(|b| Ok::<_, ()>(&b[from..to]), |o| Ok(o[from..to].to_vec()));
+        result.unwrap()
+    }
+
+    pub fn split_once(&self, pred: &char) -> Option<(Cow<'a, OsStr>, Cow<'a, OsStr>)> {
+        let n_c = get_single_native_int_value(pred)?;
+        let p = self.native.iter().position(|&x| x == n_c)?;
+        let before = self.slice(0, p);
+        let after = self.slice(p + 1, self.native.len());
+        Some((before, after))
+    }
+
+    pub fn split_at(&self, pos: usize) -> (Cow<'a, OsStr>, Cow<'a, OsStr>) {
+        let before = self.slice(0, pos);
+        let after = self.slice(pos, self.native.len());
+        (before, after)
+    }
+
+    pub fn strip_prefix(&self, prefix: &OsStr) -> Option<Cow<'a, OsStr>> {
+        let n_prefix = to_native_int_representation(prefix);
+        let result = self.match_cow(
+            |b| b.strip_prefix(&*n_prefix).ok_or(()),
+            |o| o.strip_prefix(&*n_prefix).map(|x| x.to_vec()).ok_or(()),
+        );
+        result.ok()
+    }
+
+    pub fn strip_prefix_native(&self, prefix: &OsStr) -> Option<Cow<'a, NativeIntStr>> {
+        let n_prefix = to_native_int_representation(prefix);
+        let result = self.match_cow_native(
+            |b| b.strip_prefix(&*n_prefix).ok_or(()),
+            |o| o.strip_prefix(&*n_prefix).map(|x| x.to_vec()).ok_or(()),
+        );
+        result.ok()
+    }
+
+    fn match_cow<FnBorrow, FnOwned, Err>(
+        &self,
+        f_borrow: FnBorrow,
+        f_owned: FnOwned,
+    ) -> Result<Cow<'a, OsStr>, Err>
+    where
+        FnBorrow: FnOnce(&'a [NativeCharInt]) -> Result<&'a [NativeCharInt], Err>,
+        FnOwned: FnOnce(&Vec<NativeCharInt>) -> Result<Vec<NativeCharInt>, Err>,
+    {
+        match &self.native {
+            Cow::Borrowed(b) => {
+                let slice = f_borrow(b);
+                let os_str = slice.map(|x| from_native_int_representation(Cow::Borrowed(x)));
+                os_str
+            }
+            Cow::Owned(o) => {
+                let slice = f_owned(o);
+                let os_str = slice.map(from_native_int_representation_owned);
+                os_str.map(Cow::Owned)
+            }
+        }
+    }
+
+    fn match_cow_native<FnBorrow, FnOwned, Err>(
+        &self,
+        f_borrow: FnBorrow,
+        f_owned: FnOwned,
+    ) -> Result<Cow<'a, NativeIntStr>, Err>
+    where
+        FnBorrow: FnOnce(&'a [NativeCharInt]) -> Result<&'a [NativeCharInt], Err>,
+        FnOwned: FnOnce(&Vec<NativeCharInt>) -> Result<Vec<NativeCharInt>, Err>,
+    {
+        match &self.native {
+            Cow::Borrowed(b) => {
+                let slice = f_borrow(b);
+                slice.map(Cow::Borrowed)
+            }
+            Cow::Owned(o) => {
+                let slice = f_owned(o);
+                slice.map(Cow::Owned)
+            }
+        }
+    }
+}

src/uu/env/src/parse_error.rs

@@ -0,0 +1,55 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use std::fmt;
+
+use crate::string_parser;
+
+/// An error returned when string arg splitting fails.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum ParseError {
+    MissingClosingQuote {
+        pos: usize,
+        c: char,
+    },
+    InvalidBackslashAtEndOfStringInMinusS {
+        pos: usize,
+        quoting: String,
+    },
+    BackslashCNotAllowedInDoubleQuotes {
+        pos: usize,
+    },
+    InvalidSequenceBackslashXInMinusS {
+        pos: usize,
+        c: char,
+    },
+    ParsingOfVariableNameFailed {
+        pos: usize,
+        msg: String,
+    },
+    InternalError {
+        pos: usize,
+        sub_err: string_parser::Error,
+    },
+    ReachedEnd,
+    ContinueWithDelimiter,
+}
+
+impl fmt::Display for ParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(format!("{:?}", self).as_str())
+    }
+}
+
+impl std::error::Error for ParseError {}
+
+impl From<string_parser::Error> for ParseError {
+    fn from(value: string_parser::Error) -> Self {
+        Self::InternalError {
+            pos: value.peek_position,
+            sub_err: value,
+        }
+    }
+}

src/uu/env/src/split_iterator.rs

@@ -0,0 +1,375 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+//
+// This file is based on work from Tomasz Miąsko who published it as "shell_words" crate,
+// licensed under the Apache License, Version 2.0 <LICENSE-APACHE>
+// or the MIT license <LICENSE-MIT>, at your option.
+//
+//! Process command line according to parsing rules of original GNU env.
+//! Even though it looks quite like a POSIX syntax, the original
+//! "shell_words" implementation had to be adapted significantly.
+//!
+//! Apart from the grammar differences, there is a new feature integrated: $VARIABLE expansion.
+//!
+//! [GNU env] <https://www.gnu.org/software/coreutils/manual/html_node/env-invocation.html#g_t_002dS_002f_002d_002dsplit_002dstring-syntax>
+// spell-checker:ignore (words) Tomasz Miąsko rntfv FFFD varname
+
+#![forbid(unsafe_code)]
+
+use std::borrow::Cow;
+
+use crate::native_int_str::from_native_int_representation;
+use crate::native_int_str::NativeCharInt;
+use crate::native_int_str::NativeIntStr;
+use crate::native_int_str::NativeIntString;
+use crate::parse_error::ParseError;
+use crate::string_expander::StringExpander;
+use crate::string_parser::StringParser;
+use crate::variable_parser::VariableParser;
+
+const BACKSLASH: char = '\\';
+const DOUBLE_QUOTES: char = '\"';
+const SINGLE_QUOTES: char = '\'';
+const NEW_LINE: char = '\n';
+const DOLLAR: char = '$';
+
+const REPLACEMENTS: [(char, char); 9] = [
+    ('r', '\r'),
+    ('n', '\n'),
+    ('t', '\t'),
+    ('f', '\x0C'),
+    ('v', '\x0B'),
+    ('_', ' '),
+    ('#', '#'),
+    ('$', '$'),
+    ('"', '"'),
+];
+
+const ASCII_WHITESPACE_CHARS: [char; 6] = [' ', '\t', '\r', '\n', '\x0B', '\x0C'];
+
+pub struct SplitIterator<'a> {
+    expander: StringExpander<'a>,
+    words: Vec<Vec<NativeCharInt>>,
+}
+
+impl<'a> SplitIterator<'a> {
+    pub fn new(s: &'a NativeIntStr) -> Self {
+        Self {
+            expander: StringExpander::new(s),
+            words: Vec::new(),
+        }
+    }
+
+    fn skip_one(&mut self) -> Result<(), ParseError> {
+        self.expander
+            .get_parser_mut()
+            .consume_one_ascii_or_all_non_ascii()?;
+        Ok(())
+    }
+
+    fn take_one(&mut self) -> Result<(), ParseError> {
+        Ok(self.expander.take_one()?)
+    }
+
+    fn get_current_char(&self) -> Option<char> {
+        self.expander.peek().ok()
+    }
+
+    fn push_char_to_word(&mut self, c: char) {
+        self.expander.put_one_char(c);
+    }
+
+    fn push_word_to_words(&mut self) {
+        let word = self.expander.take_collected_output();
+        self.words.push(word);
+    }
+
+    fn get_parser(&self) -> &StringParser<'a> {
+        self.expander.get_parser()
+    }
+
+    fn get_parser_mut(&mut self) -> &mut StringParser<'a> {
+        self.expander.get_parser_mut()
+    }
+
+    fn substitute_variable<'x>(&'x mut self) -> Result<(), ParseError> {
+        let mut var_parse = VariableParser::<'a, '_> {
+            parser: self.get_parser_mut(),
+        };
+
+        let (name, default) = var_parse.parse_variable()?;
+
+        let varname_os_str_cow = from_native_int_representation(Cow::Borrowed(name));
+        let value = std::env::var_os(varname_os_str_cow);
+        match (&value, default) {
+            (None, None) => {} // do nothing, just replace it with ""
+            (Some(value), _) => {
+                self.expander.put_string(value);
+            }
+            (None, Some(default)) => {
+                self.expander.put_native_string(default);
+            }
+        };
+
+        Ok(())
+    }
+
+    fn check_and_replace_ascii_escape_code(&mut self, c: char) -> Result<bool, ParseError> {
+        if let Some(replace) = REPLACEMENTS.iter().find(|&x| x.0 == c) {
+            self.skip_one()?;
+            self.push_char_to_word(replace.1);
+            return Ok(true);
+        }
+
+        Ok(false)
+    }
+
+    fn make_invalid_sequence_backslash_xin_minus_s(&self, c: char) -> ParseError {
+        ParseError::InvalidSequenceBackslashXInMinusS {
+            pos: self.expander.get_parser().get_peek_position(),
+            c,
+        }
+    }
+
+    fn state_root(&mut self) -> Result<(), ParseError> {
+        loop {
+            match self.state_delimiter() {
+                Err(ParseError::ContinueWithDelimiter) => {}
+                Err(ParseError::ReachedEnd) => return Ok(()),
+                result => return result,
+            }
+        }
+    }
+
+    fn state_delimiter(&mut self) -> Result<(), ParseError> {
+        loop {
+            match self.get_current_char() {
+                None => return Ok(()),
+                Some('#') => {
+                    self.skip_one()?;
+                    self.state_comment()?;
+                }
+                Some(BACKSLASH) => {
+                    self.skip_one()?;
+                    self.state_delimiter_backslash()?;
+                }
+                Some(c) if ASCII_WHITESPACE_CHARS.contains(&c) => {
+                    self.skip_one()?;
+                }
+                Some(_) => {
+                    // Don't consume char. Will be done in unquoted state.
+                    self.state_unquoted()?;
+                }
+            }
+        }
+    }
+
+    fn state_delimiter_backslash(&mut self) -> Result<(), ParseError> {
+        match self.get_current_char() {
+            None => Err(ParseError::InvalidBackslashAtEndOfStringInMinusS {
+                pos: self.get_parser().get_peek_position(),
+                quoting: "Delimiter".into(),
+            }),
+            Some('_') | Some(NEW_LINE) => {
+                self.skip_one()?;
+                Ok(())
+            }
+            Some(DOLLAR) | Some(BACKSLASH) | Some('#') | Some(SINGLE_QUOTES)
+            | Some(DOUBLE_QUOTES) => {
+                self.take_one()?;
+                self.state_unquoted()
+            }
+            Some('c') => Err(ParseError::ReachedEnd),
+            Some(c) if self.check_and_replace_ascii_escape_code(c)? => self.state_unquoted(),
+            Some(c) => Err(self.make_invalid_sequence_backslash_xin_minus_s(c)),
+        }
+    }
+
+    fn state_unquoted(&mut self) -> Result<(), ParseError> {
+        loop {
+            match self.get_current_char() {
+                None => {
+                    self.push_word_to_words();
+                    return Err(ParseError::ReachedEnd);
+                }
+                Some(DOLLAR) => {
+                    self.substitute_variable()?;
+                }
+                Some(SINGLE_QUOTES) => {
+                    self.skip_one()?;
+                    self.state_single_quoted()?;
+                }
+                Some(DOUBLE_QUOTES) => {
+                    self.skip_one()?;
+                    self.state_double_quoted()?;
+                }
+                Some(BACKSLASH) => {
+                    self.skip_one()?;
+                    self.state_unquoted_backslash()?;
+                }
+                Some(c) if ASCII_WHITESPACE_CHARS.contains(&c) => {
+                    self.push_word_to_words();
+                    self.skip_one()?;
+                    return Ok(());
+                }
+                Some(_) => {
+                    self.take_one()?;
+                }
+            }
+        }
+    }
+
+    fn state_unquoted_backslash(&mut self) -> Result<(), ParseError> {
+        match self.get_current_char() {
+            None => Err(ParseError::InvalidBackslashAtEndOfStringInMinusS {
+                pos: self.get_parser().get_peek_position(),
+                quoting: "Unquoted".into(),
+            }),
+            Some(NEW_LINE) => {
+                self.skip_one()?;
+                Ok(())
+            }
+            Some('_') => {
+                self.skip_one()?;
+                self.push_word_to_words();
+                Err(ParseError::ContinueWithDelimiter)
+            }
+            Some('c') => {
+                self.push_word_to_words();
+                Err(ParseError::ReachedEnd)
+            }
+            Some(DOLLAR) | Some(BACKSLASH) | Some(SINGLE_QUOTES) | Some(DOUBLE_QUOTES) => {
+                self.take_one()?;
+                Ok(())
+            }
+            Some(c) if self.check_and_replace_ascii_escape_code(c)? => Ok(()),
+            Some(c) => Err(self.make_invalid_sequence_backslash_xin_minus_s(c)),
+        }
+    }
+
+    fn state_single_quoted(&mut self) -> Result<(), ParseError> {
+        loop {
+            match self.get_current_char() {
+                None => {
+                    return Err(ParseError::MissingClosingQuote {
+                        pos: self.get_parser().get_peek_position(),
+                        c: '\'',
+                    })
+                }
+                Some(SINGLE_QUOTES) => {
+                    self.skip_one()?;
+                    return Ok(());
+                }
+                Some(BACKSLASH) => {
+                    self.skip_one()?;
+                    self.split_single_quoted_backslash()?;
+                }
+                Some(_) => {
+                    self.take_one()?;
+                }
+            }
+        }
+    }
+
+    fn split_single_quoted_backslash(&mut self) -> Result<(), ParseError> {
+        match self.get_current_char() {
+            None => Err(ParseError::MissingClosingQuote {
+                pos: self.get_parser().get_peek_position(),
+                c: '\'',
+            }),
+            Some(NEW_LINE) => {
+                self.skip_one()?;
+                Ok(())
+            }
+            Some(SINGLE_QUOTES) | Some(BACKSLASH) => {
+                self.take_one()?;
+                Ok(())
+            }
+            Some(c) if REPLACEMENTS.iter().any(|&x| x.0 == c) => {
+                // See GNU test-suite e11: In single quotes, \t remains as it is.
+                // Comparing with GNU behavior: \a is not accepted and issues an error.
+                // So apparently only known sequences are allowed, even though they are not expanded.... bug of GNU?
+                self.push_char_to_word(BACKSLASH);
+                self.take_one()?;
+                Ok(())
+            }
+            Some(c) => Err(self.make_invalid_sequence_backslash_xin_minus_s(c)),
+        }
+    }
+
+    fn state_double_quoted(&mut self) -> Result<(), ParseError> {
+        loop {
+            match self.get_current_char() {
+                None => {
+                    return Err(ParseError::MissingClosingQuote {
+                        pos: self.get_parser().get_peek_position(),
+                        c: '"',
+                    })
+                }
+                Some(DOLLAR) => {
+                    self.substitute_variable()?;
+                }
+                Some(DOUBLE_QUOTES) => {
+                    self.skip_one()?;
+                    return Ok(());
+                }
+                Some(BACKSLASH) => {
+                    self.skip_one()?;
+                    self.state_double_quoted_backslash()?;
+                }
+                Some(_) => {
+                    self.take_one()?;
+                }
+            }
+        }
+    }
+
+    fn state_double_quoted_backslash(&mut self) -> Result<(), ParseError> {
+        match self.get_current_char() {
+            None => Err(ParseError::MissingClosingQuote {
+                pos: self.get_parser().get_peek_position(),
+                c: '"',
+            }),
+            Some(NEW_LINE) => {
+                self.skip_one()?;
+                Ok(())
+            }
+            Some(DOUBLE_QUOTES) | Some(DOLLAR) | Some(BACKSLASH) => {
+                self.take_one()?;
+                Ok(())
+            }
+            Some('c') => Err(ParseError::BackslashCNotAllowedInDoubleQuotes {
+                pos: self.get_parser().get_peek_position(),
+            }),
+            Some(c) if self.check_and_replace_ascii_escape_code(c)? => Ok(()),
+            Some(c) => Err(self.make_invalid_sequence_backslash_xin_minus_s(c)),
+        }
+    }
+
+    fn state_comment(&mut self) -> Result<(), ParseError> {
+        loop {
+            match self.get_current_char() {
+                None => return Err(ParseError::ReachedEnd),
+                Some(NEW_LINE) => {
+                    self.skip_one()?;
+                    return Ok(());
+                }
+                Some(_) => {
+                    self.get_parser_mut().skip_until_char_or_end(NEW_LINE);
+                }
+            }
+        }
+    }
+
+    pub fn split(mut self) -> Result<Vec<NativeIntString>, ParseError> {
+        self.state_root()?;
+        Ok(self.words)
+    }
+}
+
+pub fn split(s: &NativeIntStr) -> Result<Vec<NativeIntString>, ParseError> {
+    let splitted_args = SplitIterator::new(s).split()?;
+    Ok(splitted_args)
+}

src/uu/env/src/string_expander.rs

@@ -0,0 +1,92 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use std::{
+    ffi::{OsStr, OsString},
+    mem,
+    ops::Deref,
+};
+
+use crate::{
+    native_int_str::{to_native_int_representation, NativeCharInt, NativeIntStr},
+    string_parser::{Chunk, Error, StringParser},
+};
+
+/// This class makes parsing and word collection more convenient.
+///
+/// It manages an "output" buffer that is automatically filled.
+/// It provides "skip_one" and "take_one" that focus on
+/// working with ASCII separators. Thus they will skip or take
+/// all consecutive non-ascii char sequences at once.
+pub struct StringExpander<'a> {
+    parser: StringParser<'a>,
+    output: Vec<NativeCharInt>,
+}
+
+impl<'a> StringExpander<'a> {
+    pub fn new(input: &'a NativeIntStr) -> Self {
+        Self {
+            parser: StringParser::new(input),
+            output: Vec::default(),
+        }
+    }
+
+    pub fn new_at(input: &'a NativeIntStr, pos: usize) -> Self {
+        Self {
+            parser: StringParser::new_at(input, pos),
+            output: Vec::default(),
+        }
+    }
+
+    pub fn get_parser(&self) -> &StringParser<'a> {
+        &self.parser
+    }
+
+    pub fn get_parser_mut(&mut self) -> &mut StringParser<'a> {
+        &mut self.parser
+    }
+
+    pub fn peek(&self) -> Result<char, Error> {
+        self.parser.peek()
+    }
+
+    pub fn skip_one(&mut self) -> Result<(), Error> {
+        self.get_parser_mut().consume_one_ascii_or_all_non_ascii()?;
+        Ok(())
+    }
+
+    pub fn get_peek_position(&self) -> usize {
+        self.get_parser().get_peek_position()
+    }
+
+    pub fn take_one(&mut self) -> Result<(), Error> {
+        let chunks = self.parser.consume_one_ascii_or_all_non_ascii()?;
+        for chunk in chunks {
+            match chunk {
+                Chunk::InvalidEncoding(invalid) => self.output.extend(invalid),
+                Chunk::ValidSingleIntChar((_c, ni)) => self.output.push(ni),
+            }
+        }
+        Ok(())
+    }
+
+    pub fn put_one_char(&mut self, c: char) {
+        let os_str = OsString::from(c.to_string());
+        self.put_string(os_str);
+    }
+
+    pub fn put_string<S: AsRef<OsStr>>(&mut self, os_str: S) {
+        let native = to_native_int_representation(os_str.as_ref());
+        self.output.extend(native.deref());
+    }
+
+    pub fn put_native_string(&mut self, n_str: &NativeIntStr) {
+        self.output.extend(n_str);
+    }
+
+    pub fn take_collected_output(&mut self) -> Vec<NativeCharInt> {
+        mem::take(&mut self.output)
+    }
+}

src/uu/env/src/string_parser.rs

@@ -0,0 +1,182 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+//
+// spell-checker:ignore (words) splitted FFFD
+#![forbid(unsafe_code)]
+
+use std::{borrow::Cow, ffi::OsStr};
+
+use crate::native_int_str::{
+    from_native_int_representation, get_char_from_native_int, get_single_native_int_value,
+    NativeCharInt, NativeIntStr,
+};
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Error {
+    pub peek_position: usize,
+    pub err_type: ErrorType,
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum ErrorType {
+    EndOfInput,
+    InternalError,
+}
+
+/// Provides a valid char or a invalid sequence of bytes.
+///
+/// Invalid byte sequences can't be splitted in any meaningful way.
+/// Thus, they need to be consumed as one piece.
+pub enum Chunk<'a> {
+    InvalidEncoding(&'a NativeIntStr),
+    ValidSingleIntChar((char, NativeCharInt)),
+}
+
+/// This class makes parsing a OsString char by char more convenient.
+///
+/// It also allows to capturing of intermediate positions for later splitting.
+pub struct StringParser<'a> {
+    input: &'a NativeIntStr,
+    pointer: usize,
+    remaining: &'a NativeIntStr,
+}
+
+impl<'a> StringParser<'a> {
+    pub fn new(input: &'a NativeIntStr) -> Self {
+        let mut instance = Self {
+            input,
+            pointer: 0,
+            remaining: input,
+        };
+        instance.set_pointer(0);
+        instance
+    }
+
+    pub fn new_at(input: &'a NativeIntStr, pos: usize) -> Self {
+        let mut instance = Self::new(input);
+        instance.set_pointer(pos);
+        instance
+    }
+
+    pub fn get_input(&self) -> &'a NativeIntStr {
+        self.input
+    }
+
+    pub fn get_peek_position(&self) -> usize {
+        self.pointer
+    }
+
+    pub fn peek(&self) -> Result<char, Error> {
+        self.peek_char_at_pointer(self.pointer)
+    }
+
+    fn make_err(&self, err_type: ErrorType) -> Error {
+        Error {
+            peek_position: self.get_peek_position(),
+            err_type,
+        }
+    }
+
+    pub fn peek_char_at_pointer(&self, at_pointer: usize) -> Result<char, Error> {
+        let split = self.input.split_at(at_pointer).1;
+        if split.is_empty() {
+            return Err(self.make_err(ErrorType::EndOfInput));
+        }
+        if let Some((c, _ni)) = get_char_from_native_int(split[0]) {
+            Ok(c)
+        } else {
+            Ok('\u{FFFD}')
+        }
+    }
+
+    fn get_chunk_with_length_at(&self, pointer: usize) -> Result<(Chunk<'a>, usize), Error> {
+        let (_before, after) = self.input.split_at(pointer);
+        if after.is_empty() {
+            return Err(self.make_err(ErrorType::EndOfInput));
+        }
+
+        if let Some(c_ni) = get_char_from_native_int(after[0]) {
+            Ok((Chunk::ValidSingleIntChar(c_ni), 1))
+        } else {
+            let mut i = 1;
+            while i < after.len() {
+                if let Some(_c) = get_char_from_native_int(after[i]) {
+                    break;
+                }
+                i += 1;
+            }
+
+            let chunk = &after[0..i];
+            Ok((Chunk::InvalidEncoding(chunk), chunk.len()))
+        }
+    }
+
+    pub fn peek_chunk(&self) -> Option<Chunk<'a>> {
+        return self
+            .get_chunk_with_length_at(self.pointer)
+            .ok()
+            .map(|(chunk, _)| chunk);
+    }
+
+    pub fn consume_chunk(&mut self) -> Result<Chunk<'a>, Error> {
+        let (chunk, len) = self.get_chunk_with_length_at(self.pointer)?;
+        self.set_pointer(self.pointer + len);
+        Ok(chunk)
+    }
+
+    pub fn consume_one_ascii_or_all_non_ascii(&mut self) -> Result<Vec<Chunk<'a>>, Error> {
+        let mut result = Vec::<Chunk<'a>>::new();
+        loop {
+            let data = self.consume_chunk()?;
+            let was_ascii = if let Chunk::ValidSingleIntChar((c, _ni)) = &data {
+                c.is_ascii()
+            } else {
+                false
+            };
+            result.push(data);
+            if was_ascii {
+                return Ok(result);
+            }
+
+            match self.peek_chunk() {
+                Some(Chunk::ValidSingleIntChar((c, _ni))) if c.is_ascii() => return Ok(result),
+                None => return Ok(result),
+                _ => {}
+            }
+        }
+    }
+
+    pub fn skip_multiple(&mut self, skip_byte_count: usize) {
+        let end_ptr = self.pointer + skip_byte_count;
+        self.set_pointer(end_ptr);
+    }
+
+    pub fn skip_until_char_or_end(&mut self, c: char) {
+        let native_rep = get_single_native_int_value(&c).unwrap();
+        let pos = self.remaining.iter().position(|x| *x == native_rep);
+
+        if let Some(pos) = pos {
+            self.set_pointer(self.pointer + pos);
+        } else {
+            self.set_pointer(self.input.len());
+        }
+    }
+
+    pub fn substring(&self, range: &std::ops::Range<usize>) -> &'a NativeIntStr {
+        let (_before1, after1) = self.input.split_at(range.start);
+        let (middle, _after2) = after1.split_at(range.end - range.start);
+        middle
+    }
+
+    pub fn peek_remaining(&self) -> Cow<'a, OsStr> {
+        from_native_int_representation(Cow::Borrowed(self.remaining))
+    }
+
+    pub fn set_pointer(&mut self, new_pointer: usize) {
+        self.pointer = new_pointer;
+        let (_before, after) = self.input.split_at(self.pointer);
+        self.remaining = after;
+    }
+}

src/uu/env/src/variable_parser.rs

@@ -0,0 +1,158 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use std::ops::Range;
+
+use crate::{native_int_str::NativeIntStr, parse_error::ParseError, string_parser::StringParser};
+
+pub struct VariableParser<'a, 'b> {
+    pub parser: &'b mut StringParser<'a>,
+}
+
+impl<'a, 'b> VariableParser<'a, 'b> {
+    fn get_current_char(&self) -> Option<char> {
+        self.parser.peek().ok()
+    }
+
+    fn check_variable_name_start(&self) -> Result<(), ParseError> {
+        if let Some(c) = self.get_current_char() {
+            if c.is_ascii_digit() {
+                return Err(ParseError::ParsingOfVariableNameFailed {
+                    pos: self.parser.get_peek_position(),
+                    msg: format!("Unexpected character: '{}', expected variable name must not start with 0..9", c) });
+            }
+        }
+        Ok(())
+    }
+
+    fn skip_one(&mut self) -> Result<(), ParseError> {
+        self.parser.consume_chunk()?;
+        Ok(())
+    }
+
+    fn parse_braced_variable_name(
+        &mut self,
+    ) -> Result<(&'a NativeIntStr, Option<&'a NativeIntStr>), ParseError> {
+        let pos_start = self.parser.get_peek_position();
+
+        self.check_variable_name_start()?;
+
+        let (varname_end, default_end);
+        loop {
+            match self.get_current_char() {
+                None => {
+                    return Err(ParseError::ParsingOfVariableNameFailed {
+                        pos: self.parser.get_peek_position(), msg: "Missing closing brace".into() })
+                },
+                Some(c) if !c.is_ascii() || c.is_ascii_alphanumeric() || c == '_' => {
+                    self.skip_one()?;
+                }
+                Some(':') => {
+                    varname_end = self.parser.get_peek_position();
+                    loop {
+                        match self.get_current_char() {
+                            None => {
+                                return Err(ParseError::ParsingOfVariableNameFailed {
+                                    pos: self.parser.get_peek_position(),
+                                    msg: "Missing closing brace after default value".into() })
+                            },
+                            Some('}') => {
+                                default_end = Some(self.parser.get_peek_position());
+                                self.skip_one()?;
+                                break
+                            },
+                            Some(_) => {
+                                self.skip_one()?;
+                            },
+                        }
+                    }
+                    break;
+                },
+                Some('}') => {
+                    varname_end = self.parser.get_peek_position();
+                    default_end = None;
+                    self.skip_one()?;
+                    break;
+                },
+                Some(c) => {
+                    return Err(ParseError::ParsingOfVariableNameFailed {
+                        pos: self.parser.get_peek_position(),
+                        msg: format!("Unexpected character: '{}', expected a closing brace ('}}') or colon (':')", c)
+                    })
+                },
+            };
+        }
+
+        let default_opt = if let Some(default_end) = default_end {
+            Some(self.parser.substring(&Range {
+                start: varname_end + 1,
+                end: default_end,
+            }))
+        } else {
+            None
+        };
+
+        let varname = self.parser.substring(&Range {
+            start: pos_start,
+            end: varname_end,
+        });
+
+        Ok((varname, default_opt))
+    }
+
+    fn parse_unbraced_variable_name(&mut self) -> Result<&'a NativeIntStr, ParseError> {
+        let pos_start = self.parser.get_peek_position();
+
+        self.check_variable_name_start()?;
+
+        loop {
+            match self.get_current_char() {
+                None => break,
+                Some(c) if c.is_ascii_alphanumeric() || c == '_' => {
+                    self.skip_one()?;
+                }
+                Some(_) => break,
+            };
+        }
+
+        let pos_end = self.parser.get_peek_position();
+
+        if pos_end == pos_start {
+            return Err(ParseError::ParsingOfVariableNameFailed {
+                pos: pos_start,
+                msg: "Missing variable name".into(),
+            });
+        }
+
+        let varname = self.parser.substring(&Range {
+            start: pos_start,
+            end: pos_end,
+        });
+
+        Ok(varname)
+    }
+
+    pub fn parse_variable(
+        &mut self,
+    ) -> Result<(&'a NativeIntStr, Option<&'a NativeIntStr>), ParseError> {
+        self.skip_one()?;
+
+        let (name, default) = match self.get_current_char() {
+            None => {
+                return Err(ParseError::ParsingOfVariableNameFailed {
+                    pos: self.parser.get_peek_position(),
+                    msg: "missing variable name".into(),
+                })
+            }
+            Some('{') => {
+                self.skip_one()?;
+                self.parse_braced_variable_name()?
+            }
+            Some(_) => (self.parse_unbraced_variable_name()?, None),
+        };
+
+        Ok((name, default))
+    }
+}

tests/by-util/test_env.rs

@@ -2,9 +2,12 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
-// spell-checker:ignore (words) bamf chdir rlimit prlimit COMSPEC
+// spell-checker:ignore (words) bamf chdir rlimit prlimit COMSPEC cout cerr FFFD
 
+#[cfg(target_os = "linux")]
+use crate::common::util::expected_result;
 use crate::common::util::TestScenario;
+use ::env::native_int_str::{Convert, NCvt};
 use std::env;
 use std::path::Path;
 use tempfile::tempdir;
@@ -34,11 +37,24 @@ fn test_env_version() {
 
 #[test]
 fn test_echo() {
-    let result = new_ucmd!().arg("echo").arg("FOO-bar").succeeds();
+    #[cfg(target_os = "windows")]
+    let args = ["cmd", "/d/c", "echo"];
+    #[cfg(not(target_os = "windows"))]
+    let args = ["echo"];
+
+    let result = new_ucmd!().args(&args).arg("FOO-bar").succeeds();
 
     assert_eq!(result.stdout_str().trim(), "FOO-bar");
 }
 
+#[cfg(target_os = "windows")]
+#[test]
+fn test_if_windows_batch_files_can_be_executed() {
+    let result = new_ucmd!().arg("./runBat.bat").succeeds();
+
+    assert!(result.stdout_str().contains("Hello Windows World!"));
+}
+
 #[test]
 fn test_file_option() {
     let out = new_ucmd!()
@@ -245,3 +261,935 @@ fn test_fail_change_directory() {
         .stderr_move_str();
     assert!(out.contains("env: cannot change directory to "));
 }
+
+#[cfg(not(target_os = "windows"))] // windows has no executable "echo", its only supported as part of a batch-file
+#[test]
+fn test_split_string_into_args_one_argument_no_quotes() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene
+        .ucmd()
+        .arg("-S echo hello world")
+        .succeeds()
+        .stdout_move_str();
+    assert_eq!(out, "hello world\n");
+}
+
+#[cfg(not(target_os = "windows"))] // windows has no executable "echo", its only supported as part of a batch-file
+#[test]
+fn test_split_string_into_args_one_argument() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene
+        .ucmd()
+        .arg("-S echo \"hello world\"")
+        .succeeds()
+        .stdout_move_str();
+    assert_eq!(out, "hello world\n");
+}
+
+#[cfg(not(target_os = "windows"))] // windows has no executable "echo", its only supported as part of a batch-file
+#[test]
+fn test_split_string_into_args_s_escaping_challenge() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene
+        .ucmd()
+        .args(&[r#"-S echo "hello \"great\" world""#])
+        .succeeds()
+        .stdout_move_str();
+    assert_eq!(out, "hello \"great\" world\n");
+}
+
+#[test]
+fn test_split_string_into_args_s_escaped_c_not_allowed() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene.ucmd().args(&[r#"-S"\c""#]).fails().stderr_move_str();
+    assert_eq!(
+        out,
+        "env: '\\c' must not appear in double-quoted -S string\n"
+    );
+}
+
+#[cfg(not(target_os = "windows"))] // no printf available
+#[test]
+fn test_split_string_into_args_s_whitespace_handling() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene
+        .ucmd()
+        .args(&["-Sprintf x%sx\\n A \t B \x0B\x0C\r\n"])
+        .succeeds()
+        .stdout_move_str();
+    assert_eq!(out, "xAx\nxBx\n");
+}
+
+#[cfg(not(target_os = "windows"))] // no printf available
+#[test]
+fn test_split_string_into_args_long_option_whitespace_handling() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene
+        .ucmd()
+        .args(&["--split-string printf x%sx\\n A \t B \x0B\x0C\r\n"])
+        .succeeds()
+        .stdout_move_str();
+    assert_eq!(out, "xAx\nxBx\n");
+}
+
+#[cfg(not(target_os = "windows"))] // no printf available
+#[test]
+fn test_split_string_into_args_debug_output_whitespace_handling() {
+    let scene = TestScenario::new(util_name!());
+
+    let out = scene
+        .ucmd()
+        .args(&["-vS printf x%sx\\n A \t B \x0B\x0C\r\n"])
+        .succeeds();
+    assert_eq!(out.stdout_str(), "xAx\nxBx\n");
+    assert_eq!(out.stderr_str(), "input args:\narg[0]: 'env'\narg[1]: $'-vS printf x%sx\\\\n A \\t B \\x0B\\x0C\\r\\n'\nexecutable: 'printf'\narg[0]: $'x%sx\\n'\narg[1]: 'A'\narg[2]: 'B'\n");
+}
+
+// FixMe: This test fails on MACOS:
+// thread 'test_env::test_gnu_e20' panicked at 'assertion failed: `(left == right)`
+// left: `"A=B C=D\n__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0\n"`,
+// right: `"A=B C=D\n"`', tests/by-util/test_env.rs:369:5
+#[cfg(not(target_os = "macos"))]
+#[test]
+fn test_gnu_e20() {
+    let scene = TestScenario::new(util_name!());
+
+    let env_bin = String::from(crate::common::util::TESTS_BINARY) + " " + util_name!();
+
+    let (input, output) = (
+        [
+            String::from("-i"),
+            String::from(r#"-SA="B\_C=D" "#) + env_bin.escape_default().to_string().as_str() + "",
+        ],
+        "A=B C=D\n",
+    );
+
+    let out = scene.ucmd().args(&input).succeeds();
+    assert_eq!(out.stdout_str(), output);
+}
+
+#[test]
+fn test_split_string_misc() {
+    use ::env::native_int_str::NCvt;
+    use ::env::parse_args_from_str;
+
+    assert_eq!(
+        NCvt::convert(vec!["A=B", "FOO=AR", "sh", "-c", "echo $A$FOO"]),
+        parse_args_from_str(&NCvt::convert(r#"A=B FOO=AR  sh -c "echo \$A\$FOO""#)).unwrap(),
+    );
+    assert_eq!(
+        NCvt::convert(vec!["A=B", "FOO=AR", "sh", "-c", "echo $A$FOO"]),
+        parse_args_from_str(&NCvt::convert(r#"A=B FOO=AR  sh -c 'echo $A$FOO'"#)).unwrap()
+    );
+    assert_eq!(
+        NCvt::convert(vec!["A=B", "FOO=AR", "sh", "-c", "echo $A$FOO"]),
+        parse_args_from_str(&NCvt::convert(r#"A=B FOO=AR  sh -c 'echo $A$FOO'"#)).unwrap()
+    );
+
+    assert_eq!(
+        NCvt::convert(vec!["-i", "A=B ' C"]),
+        parse_args_from_str(&NCvt::convert(r#"-i A='B \' C'"#)).unwrap()
+    );
+}
+
+#[test]
+fn test_split_string_environment_vars_test() {
+    std::env::set_var("FOO", "BAR");
+    assert_eq!(
+        NCvt::convert(vec!["FOO=bar", "sh", "-c", "echo xBARx =$FOO="]),
+        ::env::parse_args_from_str(&NCvt::convert(r#"FOO=bar sh -c "echo x${FOO}x =\$FOO=""#))
+            .unwrap(),
+    );
+}
+
+#[macro_export]
+macro_rules! compare_with_gnu {
+    ( $ts:expr, $args:expr ) => {{
+        println!("==========================================================================");
+        let result = $ts.ucmd().args($args).run();
+
+        #[cfg(target_os = "linux")]
+        {
+            let reference = expected_result(&$ts, $args);
+            if let Ok(reference) = reference {
+                let success = result.code() == reference.code()
+                    && result.stdout_str() == reference.stdout_str()
+                    && result.stderr_str() == reference.stderr_str();
+                if !success {
+                    println!("reference.code: {}", reference.code());
+                    println!("   result.code: {}", result.code());
+                    println!("reference.cout: {}", reference.stdout_str());
+                    println!("   result.cout: {}", result.stdout_str());
+                    println!("reference.cerr: {}", reference.stderr_str_lossy());
+                    println!("   result.cerr: {}", result.stderr_str_lossy());
+                }
+                assert_eq!(result.code(), reference.code());
+                assert_eq!(result.stdout_str(), reference.stdout_str());
+                assert_eq!(result.stderr_str(), reference.stderr_str());
+            } else {
+                println!(
+                    "gnu reference test skipped. Reason: {:?}",
+                    reference.unwrap_err()
+                );
+            }
+        }
+
+        result
+    }};
+}
+
+#[test]
+fn test_env_with_gnu_reference_parsing_errors() {
+    let ts = TestScenario::new(util_name!());
+
+    compare_with_gnu!(ts, &["-S\\|echo hallo"]) // no quotes, invalid escape sequence |
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\|' in -S\n");
+
+    compare_with_gnu!(ts, &["-S\\a"]) // no quotes, invalid escape sequence a
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\a' in -S\n");
+
+    compare_with_gnu!(ts, &["-S\"\\a\""]) // double quotes, invalid escape sequence a
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\a' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S"\a""#]) // same as before, just using r#""#
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\a' in -S\n");
+
+    compare_with_gnu!(ts, &["-S'\\a'"]) // single quotes, invalid escape sequence a
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\a' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S\|\&\;"#]) // no quotes, invalid escape sequence |
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\|' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S\<\&\;"#]) // no quotes, invalid escape sequence <
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\<' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S\>\&\;"#]) // no quotes, invalid escape sequence >
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\>' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S\`\&\;"#]) // no quotes, invalid escape sequence `
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\`' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S"\`\&\;""#]) // double quotes, invalid escape sequence `
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\`' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S'\`\&\;'"#]) // single quotes, invalid escape sequence `
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\`' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S\`"#]) // ` escaped without quotes
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\`' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S"\`""#]) // ` escaped in double quotes
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\`' in -S\n");
+
+    compare_with_gnu!(ts, &[r#"-S'\`'"#]) // ` escaped in single quotes
+        .failure()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\`' in -S\n");
+
+    ts.ucmd()
+        .args(&[r#"-S\🦉"#]) // ` escaped in single quotes
+        .fails()
+        .code_is(125)
+        .no_stdout()
+        .stderr_is("env: invalid sequence '\\\u{FFFD}' in -S\n"); // gnu doesn't show the owl. Instead a invalid unicode ?
+}
+
+#[test]
+fn test_env_with_gnu_reference_empty_executable_single_quotes() {
+    let ts = TestScenario::new(util_name!());
+
+    ts.ucmd()
+        .args(&["-S''"]) // empty single quotes, considered as program name
+        .fails()
+        .code_is(127)
+        .no_stdout()
+        .stderr_is("env: '': No such file or directory\n"); // gnu version again adds escaping here
+}
+
+#[test]
+fn test_env_with_gnu_reference_empty_executable_double_quotes() {
+    let ts = TestScenario::new(util_name!());
+
+    compare_with_gnu!(ts, &["-S\"\""]) // empty double quotes, considered as program name
+        .failure()
+        .code_is(127)
+        .no_stdout()
+        .stderr_is("env: '': No such file or directory\n");
+}
+
+#[cfg(test)]
+mod tests_split_iterator {
+
+    enum EscapeStyle {
+        /// No escaping.
+        None,
+        /// Wrap in single quotes.
+        SingleQuoted,
+        /// Single quotes combined with backslash.
+        Mixed,
+    }
+
+    /// Determines escaping style to use.
+    fn escape_style(s: &str) -> EscapeStyle {
+        if s.is_empty() {
+            return EscapeStyle::SingleQuoted;
+        }
+
+        let mut special = false;
+        let mut newline = false;
+        let mut single_quote = false;
+
+        for c in s.chars() {
+            match c {
+                '\n' => {
+                    newline = true;
+                    special = true;
+                }
+                '\'' => {
+                    single_quote = true;
+                    special = true;
+                }
+                '|' | '&' | ';' | '<' | '>' | '(' | ')' | '$' | '`' | '\\' | '"' | ' ' | '\t'
+                | '*' | '?' | '[' | '#' | '˜' | '=' | '%' => {
+                    special = true;
+                }
+                _ => continue,
+            }
+        }
+
+        if !special {
+            EscapeStyle::None
+        } else if newline && !single_quote {
+            EscapeStyle::SingleQuoted
+        } else {
+            EscapeStyle::Mixed
+        }
+    }
+
+    /// Escapes special characters in a string, so that it will retain its literal
+    /// meaning when used as a part of command in Unix shell.
+    ///
+    /// It tries to avoid introducing any unnecessary quotes or escape characters,
+    /// but specifics regarding quoting style are left unspecified.
+    pub fn quote(s: &str) -> std::borrow::Cow<str> {
+        // We are going somewhat out of the way to provide
+        // minimal amount of quoting in typical cases.
+        match escape_style(s) {
+            EscapeStyle::None => s.into(),
+            EscapeStyle::SingleQuoted => format!("'{}'", s).into(),
+            EscapeStyle::Mixed => {
+                let mut quoted = String::new();
+                quoted.push('\'');
+                for c in s.chars() {
+                    if c == '\'' {
+                        quoted.push_str("'\\''");
+                    } else {
+                        quoted.push(c);
+                    }
+                }
+                quoted.push('\'');
+                quoted.into()
+            }
+        }
+    }
+
+    /// Joins arguments into a single command line suitable for execution in Unix
+    /// shell.
+    ///
+    /// Each argument is quoted using [`quote`] to preserve its literal meaning when
+    /// parsed by Unix shell.
+    ///
+    /// Note: This function is essentially an inverse of [`split`].
+    ///
+    /// # Examples
+    ///
+    /// Logging executed commands in format that can be easily copied and pasted
+    /// into an actual shell:
+    ///
+    /// ```rust,no_run
+    /// fn execute(args: &[&str]) {
+    ///     use std::process::Command;
+    ///     println!("Executing: {}", shell_words::join(args));
+    ///     Command::new(&args[0])
+    ///         .args(&args[1..])
+    ///         .spawn()
+    ///         .expect("failed to start subprocess")
+    ///         .wait()
+    ///         .expect("failed to wait for subprocess");
+    /// }
+    ///
+    /// execute(&["python", "-c", "print('Hello world!')"]);
+    /// ```
+    ///
+    /// [`quote`]: fn.quote.html
+    /// [`split`]: fn.split.html
+    pub fn join<I, S>(words: I) -> String
+    where
+        I: IntoIterator<Item = S>,
+        S: AsRef<str>,
+    {
+        let mut line = words.into_iter().fold(String::new(), |mut line, word| {
+            let quoted = quote(word.as_ref());
+            line.push_str(quoted.as_ref());
+            line.push(' ');
+            line
+        });
+        line.pop();
+        line
+    }
+
+    use std::ffi::OsString;
+
+    use ::env::parse_error::ParseError;
+    use env::native_int_str::{from_native_int_representation_owned, Convert, NCvt};
+
+    fn split(input: &str) -> Result<Vec<OsString>, ParseError> {
+        ::env::split_iterator::split(&NCvt::convert(input)).map(|vec| {
+            vec.into_iter()
+                .map(from_native_int_representation_owned)
+                .collect()
+        })
+    }
+
+    fn split_ok(cases: &[(&str, &[&str])]) {
+        for (i, &(input, expected)) in cases.iter().enumerate() {
+            match split(input) {
+                Err(actual) => {
+                    panic!(
+                        "[{i}] calling split({:?}):\nexpected: Ok({:?})\n  actual: Err({:?})\n",
+                        input, expected, actual
+                    );
+                }
+                Ok(actual) => {
+                    assert!(
+                        expected == actual.as_slice(),
+                        "[{i}] After split({:?}).unwrap()\nexpected: {:?}\n  actual: {:?}\n",
+                        input,
+                        expected,
+                        actual
+                    );
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn split_empty() {
+        split_ok(&[("", &[])]);
+    }
+
+    #[test]
+    fn split_initial_whitespace_is_removed() {
+        split_ok(&[
+            ("     a", &["a"]),
+            ("\t\t\t\tbar", &["bar"]),
+            ("\t \nc", &["c"]),
+        ]);
+    }
+
+    #[test]
+    fn split_trailing_whitespace_is_removed() {
+        split_ok(&[
+            ("a  ", &["a"]),
+            ("b\t", &["b"]),
+            ("c\t \n \n \n", &["c"]),
+            ("d\n\n", &["d"]),
+        ]);
+    }
+
+    #[test]
+    fn split_carriage_return() {
+        split_ok(&[("c\ra\r'\r'\r", &["c", "a", "\r"])]);
+    }
+
+    #[test]
+    fn split_() {
+        split_ok(&[("\\'\\'", &["''"])]);
+    }
+
+    #[test]
+    fn split_single_quotes() {
+        split_ok(&[
+            (r#"''"#, &[r#""#]),
+            (r#"'a'"#, &[r#"a"#]),
+            (r#"'\\'"#, &[r#"\"#]),
+            (r#"' \\ '"#, &[r#" \ "#]),
+            (r#"'#'"#, &[r#"#"#]),
+        ]);
+    }
+
+    #[test]
+    fn split_double_quotes() {
+        split_ok(&[
+            (r#""""#, &[""]),
+            (r#""""""#, &[""]),
+            (r#""a b c' d""#, &["a b c' d"]),
+            (r#""\$""#, &["$"]),
+            (r#""`""#, &["`"]),
+            (r#""\"""#, &["\""]),
+            (r#""\\""#, &["\\"]),
+            ("\"\n\"", &["\n"]),
+            ("\"\\\n\"", &[""]),
+        ]);
+    }
+
+    #[test]
+    fn split_unquoted() {
+        split_ok(&[
+            (r#"\\|\\&\\;"#, &[r#"\|\&\;"#]),
+            (r#"\\<\\>"#, &[r#"\<\>"#]),
+            (r#"\\(\\)"#, &[r#"\(\)"#]),
+            (r#"\$"#, &[r#"$"#]),
+            (r#"\""#, &[r#"""#]),
+            (r#"\'"#, &[r#"'"#]),
+            ("\\\n", &[]),
+            (" \\\n \n", &[]),
+            ("a\nb\nc", &["a", "b", "c"]),
+            ("a\\\nb\\\nc", &["abc"]),
+            ("foo bar baz", &["foo", "bar", "baz"]),
+        ]);
+    }
+
+    #[test]
+    fn split_trailing_backslash() {
+        assert_eq!(
+            split("\\"),
+            Err(ParseError::InvalidBackslashAtEndOfStringInMinusS {
+                pos: 1,
+                quoting: "Delimiter".into()
+            })
+        );
+        assert_eq!(
+            split(" \\"),
+            Err(ParseError::InvalidBackslashAtEndOfStringInMinusS {
+                pos: 2,
+                quoting: "Delimiter".into()
+            })
+        );
+        assert_eq!(
+            split("a\\"),
+            Err(ParseError::InvalidBackslashAtEndOfStringInMinusS {
+                pos: 2,
+                quoting: "Unquoted".into()
+            })
+        );
+    }
+
+    #[test]
+    fn split_errors() {
+        assert_eq!(
+            split("'abc"),
+            Err(ParseError::MissingClosingQuote { pos: 4, c: '\'' })
+        );
+        assert_eq!(
+            split("\""),
+            Err(ParseError::MissingClosingQuote { pos: 1, c: '"' })
+        );
+        assert_eq!(
+            split("'\\"),
+            Err(ParseError::MissingClosingQuote { pos: 2, c: '\'' })
+        );
+        assert_eq!(
+            split("'\\"),
+            Err(ParseError::MissingClosingQuote { pos: 2, c: '\'' })
+        );
+        assert_eq!(
+            split(r#""$""#),
+            Err(ParseError::ParsingOfVariableNameFailed {
+                pos: 2,
+                msg: "Missing variable name".into()
+            }),
+        );
+    }
+
+    #[test]
+    fn split_error_fail_with_unknown_escape_sequences() {
+        assert_eq!(
+            split("\\a"),
+            Err(ParseError::InvalidSequenceBackslashXInMinusS { pos: 1, c: 'a' })
+        );
+        assert_eq!(
+            split("\"\\a\""),
+            Err(ParseError::InvalidSequenceBackslashXInMinusS { pos: 2, c: 'a' })
+        );
+        assert_eq!(
+            split("'\\a'"),
+            Err(ParseError::InvalidSequenceBackslashXInMinusS { pos: 2, c: 'a' })
+        );
+        assert_eq!(
+            split(r#""\a""#),
+            Err(ParseError::InvalidSequenceBackslashXInMinusS { pos: 2, c: 'a' })
+        );
+        assert_eq!(
+            split(r#"\🦉"#),
+            Err(ParseError::InvalidSequenceBackslashXInMinusS {
+                pos: 1,
+                c: '\u{FFFD}'
+            })
+        );
+    }
+
+    #[test]
+    fn split_comments() {
+        split_ok(&[
+            (r#" x # comment "#, &["x"]),
+            (r#" w1#w2 "#, &["w1#w2"]),
+            (r#"'not really a # comment'"#, &["not really a # comment"]),
+            (" a # very long comment \n b # another comment", &["a", "b"]),
+        ]);
+    }
+
+    #[test]
+    fn test_quote() {
+        assert_eq!(quote(""), "''");
+        assert_eq!(quote("'"), "''\\'''");
+        assert_eq!(quote("abc"), "abc");
+        assert_eq!(quote("a \n  b"), "'a \n  b'");
+        assert_eq!(quote("X'\nY"), "'X'\\''\nY'");
+    }
+
+    #[test]
+    fn test_join() {
+        assert_eq!(join(["a", "b", "c"]), "a b c");
+        assert_eq!(join([" ", "$", "\n"]), "' ' '$' '\n'");
+    }
+
+    #[test]
+    fn join_followed_by_split_is_identity() {
+        let cases: Vec<&[&str]> = vec![
+            &["a"],
+            &["python", "-c", "print('Hello world!')"],
+            &["echo", " arg with spaces ", "arg \' with \" quotes"],
+            &["even newlines are quoted correctly\n", "\n", "\n\n\t "],
+            &["$", "`test`"],
+            &["cat", "~user/log*"],
+            &["test", "'a \"b", "\"X'"],
+            &["empty", "", "", ""],
+        ];
+        for argv in cases {
+            let args = join(argv);
+            assert_eq!(split(&args).unwrap(), argv);
+        }
+    }
+}
+
+mod test_raw_string_parser {
+    use std::{
+        borrow::Cow,
+        ffi::{OsStr, OsString},
+    };
+
+    use env::{
+        native_int_str::{
+            from_native_int_representation, from_native_int_representation_owned,
+            to_native_int_representation, NativeStr,
+        },
+        string_expander::StringExpander,
+        string_parser,
+    };
+
+    const LEN_OWL: usize = if cfg!(target_os = "windows") { 2 } else { 4 };
+
+    #[test]
+    fn test_ascii_only_take_one_look_at_correct_data_and_end_behavior() {
+        let input = "hello";
+        let cow = to_native_int_representation(OsStr::new(input));
+        let mut uut = StringExpander::new(&cow);
+        for c in input.chars() {
+            assert_eq!(c, uut.get_parser().peek().unwrap());
+            uut.take_one().unwrap();
+        }
+        assert_eq!(
+            uut.get_parser().peek(),
+            Err(string_parser::Error {
+                peek_position: 5,
+                err_type: string_parser::ErrorType::EndOfInput
+            })
+        );
+        uut.take_one().unwrap_err();
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            input
+        );
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            ""
+        );
+    }
+
+    #[test]
+    fn test_multi_byte_codes_take_one_look_at_correct_data_and_end_behavior() {
+        let input = OsString::from("🦉🦉🦉x🦉🦉x🦉x🦉🦉🦉🦉");
+        let cow = to_native_int_representation(input.as_os_str());
+        let mut uut = StringExpander::new(&cow);
+        for _i in 0..3 {
+            assert_eq!(uut.get_parser().peek().unwrap(), '\u{FFFD}');
+            uut.take_one().unwrap();
+            assert_eq!(uut.get_parser().peek().unwrap(), 'x');
+            uut.take_one().unwrap();
+        }
+        assert_eq!(uut.get_parser().peek().unwrap(), '\u{FFFD}');
+        uut.take_one().unwrap();
+        assert_eq!(
+            uut.get_parser().peek(),
+            Err(string_parser::Error {
+                peek_position: 10 * LEN_OWL + 3,
+                err_type: string_parser::ErrorType::EndOfInput
+            })
+        );
+        uut.take_one().unwrap_err();
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            input
+        );
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            ""
+        );
+    }
+
+    #[test]
+    fn test_multi_byte_codes_put_one_ascii_start_middle_end_try_invalid_ascii() {
+        let input = OsString::from("🦉🦉🦉x🦉🦉x🦉x🦉🦉🦉🦉");
+        let cow = to_native_int_representation(input.as_os_str());
+        let owl: char = '🦉';
+        let mut uut = StringExpander::new(&cow);
+        uut.put_one_char('a');
+        for _i in 0..3 {
+            assert_eq!(uut.get_parser().peek().unwrap(), '\u{FFFD}');
+            uut.take_one().unwrap();
+            uut.put_one_char('a');
+            assert_eq!(uut.get_parser().peek().unwrap(), 'x');
+            uut.take_one().unwrap();
+            uut.put_one_char('a');
+        }
+        assert_eq!(uut.get_parser().peek().unwrap(), '\u{FFFD}');
+        uut.take_one().unwrap();
+        uut.put_one_char(owl);
+        uut.put_one_char('a');
+        assert_eq!(
+            uut.get_parser().peek(),
+            Err(string_parser::Error {
+                peek_position: LEN_OWL * 10 + 3,
+                err_type: string_parser::ErrorType::EndOfInput
+            })
+        );
+        uut.take_one().unwrap_err();
+        uut.put_one_char('a');
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            "a🦉🦉🦉axa🦉🦉axa🦉axa🦉🦉🦉🦉🦉aa"
+        );
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            ""
+        );
+    }
+
+    #[test]
+    fn test_multi_byte_codes_skip_one_take_one_skip_until_ascii_char_or_end() {
+        let input = OsString::from("🦉🦉🦉x🦉🦉x🦉x🦉🦉🦉🦉");
+        let cow = to_native_int_representation(input.as_os_str());
+        let mut uut = StringExpander::new(&cow);
+
+        uut.skip_one().unwrap(); // skip 🦉🦉🦉
+        let p = LEN_OWL * 3;
+        assert_eq!(uut.get_peek_position(), p);
+
+        uut.skip_one().unwrap(); // skip x
+        assert_eq!(uut.get_peek_position(), p + 1);
+        uut.take_one().unwrap(); // take 🦉🦉
+        let p = p + 1 + LEN_OWL * 2;
+        assert_eq!(uut.get_peek_position(), p);
+
+        uut.skip_one().unwrap(); // skip x
+        assert_eq!(uut.get_peek_position(), p + 1);
+        uut.get_parser_mut().skip_until_char_or_end('x'); // skip 🦉
+        let p = p + 1 + LEN_OWL;
+        assert_eq!(uut.get_peek_position(), p);
+        uut.take_one().unwrap(); // take x
+        uut.get_parser_mut().skip_until_char_or_end('x'); // skip 🦉🦉🦉🦉 till end
+        let p = p + 1 + LEN_OWL * 4;
+        assert_eq!(uut.get_peek_position(), p);
+
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            "🦉🦉x"
+        );
+    }
+
+    #[test]
+    fn test_multi_byte_codes_skip_multiple_ascii_bounded_good_and_bad() {
+        let input = OsString::from("🦉🦉🦉x🦉🦉x🦉x🦉🦉🦉🦉");
+        let cow = to_native_int_representation(input.as_os_str());
+        let mut uut = StringExpander::new(&cow);
+
+        uut.get_parser_mut().skip_multiple(0);
+        assert_eq!(uut.get_peek_position(), 0);
+        let p = LEN_OWL * 3;
+        uut.get_parser_mut().skip_multiple(p); // skips 🦉🦉🦉
+        assert_eq!(uut.get_peek_position(), p);
+
+        uut.take_one().unwrap(); // take x
+        assert_eq!(uut.get_peek_position(), p + 1);
+        let step = LEN_OWL * 3 + 1;
+        uut.get_parser_mut().skip_multiple(step); // skips 🦉🦉x🦉
+        let p = p + 1 + step;
+        assert_eq!(uut.get_peek_position(), p);
+        uut.take_one().unwrap(); // take x
+
+        assert_eq!(uut.get_peek_position(), p + 1);
+        let step = 4 * LEN_OWL;
+        uut.get_parser_mut().skip_multiple(step); // skips 🦉🦉🦉🦉
+        let p = p + 1 + step;
+        assert_eq!(uut.get_peek_position(), p);
+
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            "xx"
+        );
+    }
+
+    #[test]
+    fn test_multi_byte_codes_put_string_utf8_start_middle_end() {
+        let input = OsString::from("🦉🦉🦉x🦉🦉x🦉x🦉🦉🦉🦉");
+        let cow = to_native_int_representation(input.as_os_str());
+        let mut uut = StringExpander::new(&cow);
+
+        uut.put_string("🦔oo");
+        uut.take_one().unwrap(); // takes 🦉🦉🦉
+        uut.put_string("oo🦔");
+        uut.take_one().unwrap(); // take x
+        uut.get_parser_mut().skip_until_char_or_end('\n'); // skips till end
+        uut.put_string("o🦔o");
+
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            "🦔oo🦉🦉🦉oo🦔xo🦔o"
+        );
+    }
+
+    #[test]
+    fn test_multi_byte_codes_look_at_remaining_start_middle_end() {
+        let input = "🦉🦉🦉x🦉🦉x🦉x🦉🦉🦉🦉";
+        let cow = to_native_int_representation(OsStr::new(input));
+        let mut uut = StringExpander::new(&cow);
+
+        assert_eq!(uut.get_parser().peek_remaining(), OsStr::new(input));
+        uut.take_one().unwrap(); // takes 🦉🦉🦉
+        assert_eq!(uut.get_parser().peek_remaining(), OsStr::new(&input[12..]));
+        uut.get_parser_mut().skip_until_char_or_end('\n'); // skips till end
+        assert_eq!(uut.get_parser().peek_remaining(), OsStr::new(""));
+
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            "🦉🦉🦉"
+        );
+    }
+
+    #[test]
+    fn test_deal_with_invalid_encoding() {
+        let owl_invalid_part;
+        let (brace_1, brace_2);
+        #[cfg(target_os = "windows")]
+        {
+            let mut buffer = [0u16; 2];
+            let owl = '🦉'.encode_utf16(&mut buffer);
+            owl_invalid_part = owl[0];
+            brace_1 = '<'.encode_utf16(&mut buffer).to_vec();
+            brace_2 = '>'.encode_utf16(&mut buffer).to_vec();
+        }
+        #[cfg(not(target_os = "windows"))]
+        {
+            let mut buffer = [0u8; 4];
+            let owl = '🦉'.encode_utf8(&mut buffer);
+            owl_invalid_part = owl.bytes().next().unwrap();
+            brace_1 = [b'<'].to_vec();
+            brace_2 = [b'>'].to_vec();
+        }
+        let mut input_ux = brace_1;
+        input_ux.push(owl_invalid_part);
+        input_ux.extend(brace_2);
+        let input_str = from_native_int_representation(Cow::Borrowed(&input_ux));
+        let mut uut = StringExpander::new(&input_ux);
+
+        assert_eq!(uut.get_parser().peek_remaining(), input_str);
+        assert_eq!(uut.get_parser().peek().unwrap(), '<');
+        uut.take_one().unwrap(); // takes "<"
+        assert_eq!(
+            uut.get_parser().peek_remaining(),
+            NativeStr::new(&input_str).split_at(1).1
+        );
+        assert_eq!(uut.get_parser().peek().unwrap(), '\u{FFFD}');
+        uut.take_one().unwrap(); // takes owl_b
+        assert_eq!(
+            uut.get_parser().peek_remaining(),
+            NativeStr::new(&input_str).split_at(2).1
+        );
+        assert_eq!(uut.get_parser().peek().unwrap(), '>');
+        uut.get_parser_mut().skip_until_char_or_end('\n');
+        assert_eq!(uut.get_parser().peek_remaining(), OsStr::new(""));
+
+        uut.take_one().unwrap_err();
+        assert_eq!(
+            from_native_int_representation_owned(uut.take_collected_output()),
+            NativeStr::new(&input_str).split_at(2).0
+        );
+    }
+}

tests/common/util.rs

@@ -15,7 +15,6 @@ use pretty_assertions::assert_eq;
 use rlimit::setrlimit;
 #[cfg(feature = "sleep")]
 use rstest::rstest;
-#[cfg(unix)]
 use std::borrow::Cow;
 use std::collections::VecDeque;
 #[cfg(not(windows))]
@@ -352,6 +351,11 @@ impl CmdResult {
         std::str::from_utf8(&self.stderr).unwrap()
     }
 
+    /// Returns the program's standard error as a string slice, automatically handling invalid utf8
+    pub fn stderr_str_lossy(&self) -> Cow<'_, str> {
+        String::from_utf8_lossy(&self.stderr)
+    }
+
     /// Returns the program's standard error as a string
     /// consumes self
     pub fn stderr_move_str(self) -> String {
@@ -372,6 +376,14 @@ impl CmdResult {
 
     #[track_caller]
     pub fn code_is(&self, expected_code: i32) -> &Self {
+        let fails = self.code() != expected_code;
+        if fails {
+            eprintln!(
+                "stdout:\n{}\nstderr:\n{}",
+                self.stdout_str(),
+                self.stderr_str()
+            );
+        }
         assert_eq!(self.code(), expected_code);
         self
     }
@@ -395,10 +407,8 @@ impl CmdResult {
     pub fn success(&self) -> &Self {
         assert!(
             self.succeeded(),
-            "Command was expected to succeed. Exit code: {}.\nstdout = {}\n stderr = {}",
+            "Command was expected to succeed. code: {}\nstdout = {}\n stderr = {}",
-            self.exit_status()
+            self.code(),
-                .code()
-                .map_or("n/a".to_string(), |code| code.to_string()),
             self.stdout_str(),
             self.stderr_str()
         );
@@ -2674,7 +2684,7 @@ pub fn expected_result(ts: &TestScenario, args: &[&str]) -> std::result::Result<
     let (stdout, stderr): (String, String) = if cfg!(target_os = "linux") {
         (
             result.stdout_str().to_string(),
-            result.stderr_str().to_string(),
+            result.stderr_str_lossy().to_string(),
         )
     } else {
         // `host_name_for` added prefix, strip 'g' prefix from results:
@@ -2682,7 +2692,7 @@ pub fn expected_result(ts: &TestScenario, args: &[&str]) -> std::result::Result<
         let to = &from[1..];
         (
             result.stdout_str().replace(&from, to),
-            result.stderr_str().replace(&from, to),
+            result.stderr_str_lossy().replace(&from, to),
         )
     };
 

tests/fixtures/env/runBat.bat

@@ -0,0 +1 @@
+echo Hello Windows World!

util/build-gnu.sh

@@ -221,6 +221,8 @@ grep -rlE '/usr/local/bin/\s?/usr/local/bin' init.cfg tests/* | xargs -r sed -Ei
 # we should not regress our project just to match what GNU is going.
 # So, do some changes on the fly
 
+patch -N -r - -d "$path_GNU" -p 1 -i "`realpath \"$path_UUTILS/util/gnu-patches/tests_env_env-S.pl.patch\"`" || true
+
 sed -i -e "s|rm: cannot remove 'e/slink'|rm: cannot remove 'e'|g" tests/rm/fail-eacces.sh
 
 sed -i -e "s|rm: cannot remove 'a/b'|rm: cannot remove 'a'|g" tests/rm/fail-2eperm.sh

util/gnu-patches/tests_env_env-S.pl.patch

@@ -0,0 +1,47 @@
+diff --git a/tests/env/env-S.pl b/tests/env/env-S.pl
+index 710ca82cf..af7cf6efa 100755
+--- a/tests/env/env-S.pl
++++ b/tests/env/env-S.pl
+@@ -209,27 +209,28 @@ my @Tests =
+       {ERR=>"$prog: no terminating quote in -S string\n"}],
+      ['err5', q[-S'A=B\\q'], {EXIT=>125},
+       {ERR=>"$prog: invalid sequence '\\q' in -S\n"}],
+-     ['err6', q[-S'A=$B'], {EXIT=>125},
+-      {ERR=>"$prog: only \${VARNAME} expansion is supported, error at: \$B\n"}],
++     ['err6', q[-S'A=$B echo hello'], {EXIT=>0},
++      {OUT=>"hello"}],
+      ['err7', q[-S'A=${B'], {EXIT=>125},
+-      {ERR=>"$prog: only \${VARNAME} expansion is supported, " .
+-           "error at: \${B\n"}],
++      {ERR=>"$prog" . qq[: variable name issue (at 5): Missing closing brace\n]}],
+      ['err8', q[-S'A=${B%B}'], {EXIT=>125},
+-      {ERR=>"$prog: only \${VARNAME} expansion is supported, " .
+-           "error at: \${B%B}\n"}],
++      {ERR=>"$prog" . qq[: variable name issue (at 5): Unexpected character: '%', expected a closing brace ('}') or colon (':')\n]}],
+      ['err9', q[-S'A=${9B}'], {EXIT=>125},
+-      {ERR=>"$prog: only \${VARNAME} expansion is supported, " .
+-           "error at: \${9B}\n"}],
++      {ERR=>"$prog" . qq[: variable name issue (at 4): Unexpected character: '9', expected variable name must not start with 0..9\n]}],
+ 
+      # Test incorrect shebang usage (extraneous whitespace).
+      ['err_sp2', q['-v -S cat -n'], {EXIT=>125},
+-      {ERR=>"env: invalid option -- ' '\n" .
+-            "env: use -[v]S to pass options in shebang lines\n" .
+-           "Try 'env --help' for more information.\n"}],
++      {ERR=>"$prog: error: unexpected argument '- ' found\n\n" .
++            "  tip: to pass '- ' as a value, use '-- - '\n\n" .
++            "Usage: $prog [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n\n" .
++            "For more information, try '--help'.\n" .
++            "$prog: use -[v]S to pass options in shebang lines\n"}],
+      ['err_sp3', q['-v	-S cat -n'], {EXIT=>125}, # embedded tab after -v
+-      {ERR=>"env: invalid option -- '\t'\n" .
+-            "env: use -[v]S to pass options in shebang lines\n" .
+-           "Try 'env --help' for more information.\n"}],
++      {ERR=>"$prog: error: unexpected argument '-\t' found\n\n" .
++            "  tip: to pass '-\t' as a value, use '-- -\t'\n\n" .
++            "Usage: $prog [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n\n" .
++            "For more information, try '--help'.\n" .
++            "$prog: use -[v]S to pass options in shebang lines\n"}],
+ 
+      # Also diagnose incorrect shebang usage when failing to exec.
+      # This typically happens with: