1 #![unstable(feature = "process_internals", issue = "none")]
7 use crate::collections::BTreeMap;
9 use crate::env::consts::{EXE_EXTENSION, EXE_SUFFIX};
10 use crate::ffi::{OsStr, OsString};
12 use crate::io::{self, Error, ErrorKind};
14 use crate::num::NonZeroI32;
15 use crate::os::windows::ffi::{OsStrExt, OsStringExt};
16 use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle, FromRawHandle, IntoRawHandle};
17 use crate::path::{Path, PathBuf};
19 use crate::sync::Mutex;
20 use crate::sys::args::{self, Arg};
22 use crate::sys::c::NonZeroDWORD;
24 use crate::sys::fs::{File, OpenOptions};
25 use crate::sys::handle::Handle;
27 use crate::sys::pipe::{self, AnonPipe};
28 use crate::sys::stdio;
29 use crate::sys_common::process::{CommandEnv, CommandEnvs};
30 use crate::sys_common::IntoInner;
32 use libc::{c_void, EXIT_FAILURE, EXIT_SUCCESS};
34 ////////////////////////////////////////////////////////////////////////////////
36 ////////////////////////////////////////////////////////////////////////////////
38 #[derive(Clone, Debug, Eq)]
42 // This stores a UTF-16 encoded string to workaround the mismatch between
43 // Rust's OsString (WTF-8) and the Windows API string type (UTF-16).
44 // Normally converting on every API call is acceptable but here
45 // `c::CompareStringOrdinal` will be called for every use of `==`.
50 fn new<T: Into<OsString>>(key: T) -> Self {
51 EnvKey::from(key.into())
55 // Comparing Windows environment variable keys[1] are behaviourally the
56 // composition of two operations[2]:
58 // 1. Case-fold both strings. This is done using a language-independent
59 // uppercase mapping that's unique to Windows (albeit based on data from an
60 // older Unicode spec). It only operates on individual UTF-16 code units so
61 // surrogates are left unchanged. This uppercase mapping can potentially change
62 // between Windows versions.
64 // 2. Perform an ordinal comparison of the strings. A comparison using ordinal
65 // is just a comparison based on the numerical value of each UTF-16 code unit[3].
67 // Because the case-folding mapping is unique to Windows and not guaranteed to
68 // be stable, we ask the OS to compare the strings for us. This is done by
69 // calling `CompareStringOrdinal`[4] with `bIgnoreCase` set to `TRUE`.
71 // [1] https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices-strings#choosing-a-stringcomparison-member-for-your-method-call
72 // [2] https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices-strings#stringtoupper-and-stringtolower
73 // [3] https://docs.microsoft.com/en-us/dotnet/api/system.stringcomparison?view=net-5.0#System_StringComparison_Ordinal
74 // [4] https://docs.microsoft.com/en-us/windows/win32/api/stringapiset/nf-stringapiset-comparestringordinal
76 fn cmp(&self, other: &Self) -> cmp::Ordering {
78 let result = c::CompareStringOrdinal(
80 self.utf16.len() as _,
82 other.utf16.len() as _,
86 c::CSTR_LESS_THAN => cmp::Ordering::Less,
87 c::CSTR_EQUAL => cmp::Ordering::Equal,
88 c::CSTR_GREATER_THAN => cmp::Ordering::Greater,
89 // `CompareStringOrdinal` should never fail so long as the parameters are correct.
90 _ => panic!("comparing environment keys failed: {}", Error::last_os_error()),
95 impl PartialOrd for EnvKey {
96 fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
100 impl PartialEq for EnvKey {
101 fn eq(&self, other: &Self) -> bool {
102 if self.utf16.len() != other.utf16.len() {
105 self.cmp(other) == cmp::Ordering::Equal
109 impl PartialOrd<str> for EnvKey {
110 fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
111 Some(self.cmp(&EnvKey::new(other)))
114 impl PartialEq<str> for EnvKey {
115 fn eq(&self, other: &str) -> bool {
116 if self.os_string.len() != other.len() {
119 self.cmp(&EnvKey::new(other)) == cmp::Ordering::Equal
124 // Environment variable keys should preserve their original case even though
125 // they are compared using a caseless string mapping.
126 impl From<OsString> for EnvKey {
127 fn from(k: OsString) -> Self {
128 EnvKey { utf16: k.encode_wide().collect(), os_string: k }
132 impl From<EnvKey> for OsString {
133 fn from(k: EnvKey) -> Self {
138 impl From<&OsStr> for EnvKey {
139 fn from(k: &OsStr) -> Self {
140 Self::from(k.to_os_string())
144 impl AsRef<OsStr> for EnvKey {
145 fn as_ref(&self) -> &OsStr {
150 pub(crate) fn ensure_no_nuls<T: AsRef<OsStr>>(str: T) -> io::Result<T> {
151 if str.as_ref().encode_wide().any(|b| b == 0) {
152 Err(io::const_io_error!(ErrorKind::InvalidInput, "nul byte found in provided data"))
162 cwd: Option<OsString>,
164 detach: bool, // not currently exposed in std::process
165 stdin: Option<Stdio>,
166 stdout: Option<Stdio>,
167 stderr: Option<Stdio>,
168 force_quotes_enabled: bool,
179 pub struct StdioPipes {
180 pub stdin: Option<AnonPipe>,
181 pub stdout: Option<AnonPipe>,
182 pub stderr: Option<AnonPipe>,
186 pub fn new(program: &OsStr) -> Command {
188 program: program.to_os_string(),
190 env: Default::default(),
197 force_quotes_enabled: false,
201 pub fn arg(&mut self, arg: &OsStr) {
202 self.args.push(Arg::Regular(arg.to_os_string()))
204 pub fn env_mut(&mut self) -> &mut CommandEnv {
207 pub fn cwd(&mut self, dir: &OsStr) {
208 self.cwd = Some(dir.to_os_string())
210 pub fn stdin(&mut self, stdin: Stdio) {
211 self.stdin = Some(stdin);
213 pub fn stdout(&mut self, stdout: Stdio) {
214 self.stdout = Some(stdout);
216 pub fn stderr(&mut self, stderr: Stdio) {
217 self.stderr = Some(stderr);
219 pub fn creation_flags(&mut self, flags: u32) {
223 pub fn force_quotes(&mut self, enabled: bool) {
224 self.force_quotes_enabled = enabled;
227 pub fn raw_arg(&mut self, command_str_to_append: &OsStr) {
228 self.args.push(Arg::Raw(command_str_to_append.to_os_string()))
231 pub fn get_program(&self) -> &OsStr {
235 pub fn get_args(&self) -> CommandArgs<'_> {
236 let iter = self.args.iter();
240 pub fn get_envs(&self) -> CommandEnvs<'_> {
244 pub fn get_current_dir(&self) -> Option<&Path> {
245 self.cwd.as_ref().map(|cwd| Path::new(cwd))
252 ) -> io::Result<(Process, StdioPipes)> {
253 let maybe_env = self.env.capture_if_changed();
255 let mut si = zeroed_startupinfo();
256 si.cb = mem::size_of::<c::STARTUPINFO>() as c::DWORD;
257 si.dwFlags = c::STARTF_USESTDHANDLES;
259 let child_paths = if let Some(env) = maybe_env.as_ref() {
260 env.get(&EnvKey::new("PATH")).map(|s| s.as_os_str())
264 let program = resolve_exe(&self.program, || env::var_os("PATH"), child_paths)?;
265 // Case insensitive "ends_with" of UTF-16 encoded ".bat" or ".cmd"
266 let is_batch_file = matches!(
267 program.len().checked_sub(5).and_then(|i| program.get(i..)),
268 Some([46, 98 | 66, 97 | 65, 116 | 84, 0] | [46, 99 | 67, 109 | 77, 100 | 68, 0])
270 let (program, mut cmd_str) = if is_batch_file {
273 args::make_bat_command_line(
274 &args::to_user_path(program)?,
276 self.force_quotes_enabled,
280 let cmd_str = make_command_line(&self.program, &self.args, self.force_quotes_enabled)?;
283 cmd_str.push(0); // add null terminator
285 // stolen from the libuv code.
286 let mut flags = self.flags | c::CREATE_UNICODE_ENVIRONMENT;
288 flags |= c::DETACHED_PROCESS | c::CREATE_NEW_PROCESS_GROUP;
291 let (envp, _data) = make_envp(maybe_env)?;
292 let (dirp, _data) = make_dirp(self.cwd.as_ref())?;
293 let mut pi = zeroed_process_information();
295 // Prepare all stdio handles to be inherited by the child. This
296 // currently involves duplicating any existing ones with the ability to
297 // be inherited by child processes. Note, however, that once an
298 // inheritable handle is created, *any* spawned child will inherit that
299 // handle. We only want our own child to inherit this handle, so we wrap
300 // the remaining portion of this spawn in a mutex.
302 // For more information, msdn also has an article about this race:
303 // https://support.microsoft.com/kb/315939
304 static CREATE_PROCESS_LOCK: Mutex<()> = Mutex::new(());
306 let _guard = CREATE_PROCESS_LOCK.lock();
308 let mut pipes = StdioPipes { stdin: None, stdout: None, stderr: None };
309 let null = Stdio::Null;
310 let default_stdin = if needs_stdin { &default } else { &null };
311 let stdin = self.stdin.as_ref().unwrap_or(default_stdin);
312 let stdout = self.stdout.as_ref().unwrap_or(&default);
313 let stderr = self.stderr.as_ref().unwrap_or(&default);
314 let stdin = stdin.to_handle(c::STD_INPUT_HANDLE, &mut pipes.stdin)?;
315 let stdout = stdout.to_handle(c::STD_OUTPUT_HANDLE, &mut pipes.stdout)?;
316 let stderr = stderr.to_handle(c::STD_ERROR_HANDLE, &mut pipes.stderr)?;
317 si.hStdInput = stdin.as_raw_handle();
318 si.hStdOutput = stdout.as_raw_handle();
319 si.hStdError = stderr.as_raw_handle();
322 cvt(c::CreateProcessW(
324 cmd_str.as_mut_ptr(),
339 handle: Handle::from_raw_handle(pi.hProcess),
340 main_thread_handle: Handle::from_raw_handle(pi.hThread),
348 impl fmt::Debug for Command {
349 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
350 self.program.fmt(f)?;
351 for arg in &self.args {
354 Arg::Regular(s) => s.fmt(f),
355 Arg::Raw(s) => f.write_str(&s.to_string_lossy()),
362 // Resolve `exe_path` to the executable name.
364 // * If the path is simply a file name then use the paths given by `search_paths` to find the executable.
365 // * Otherwise use the `exe_path` as given.
367 // This function may also append `.exe` to the name. The rationale for doing so is as follows:
369 // It is a very strong convention that Windows executables have the `exe` extension.
370 // In Rust, it is common to omit this extension.
371 // Therefore this functions first assumes `.exe` was intended.
372 // It falls back to the plain file name if a full path is given and the extension is omitted
373 // or if only a file name is given and it already contains an extension.
376 parent_paths: impl FnOnce() -> Option<OsString>,
377 child_paths: Option<&OsStr>,
378 ) -> io::Result<Vec<u16>> {
379 // Early return if there is no filename.
380 if exe_path.is_empty() || path::has_trailing_slash(exe_path) {
381 return Err(io::const_io_error!(
382 io::ErrorKind::InvalidInput,
383 "program path has no file name",
386 // Test if the file name has the `exe` extension.
387 // This does a case-insensitive `ends_with`.
388 let has_exe_suffix = if exe_path.len() >= EXE_SUFFIX.len() {
389 exe_path.bytes()[exe_path.len() - EXE_SUFFIX.len()..]
390 .eq_ignore_ascii_case(EXE_SUFFIX.as_bytes())
395 // If `exe_path` is an absolute path or a sub-path then don't search `PATH` for it.
396 if !path::is_file_name(exe_path) {
398 // The application name is a path to a `.exe` file.
399 // Let `CreateProcessW` figure out if it exists or not.
400 return path::maybe_verbatim(Path::new(exe_path));
402 let mut path = PathBuf::from(exe_path);
404 // Append `.exe` if not already there.
405 path = path::append_suffix(path, EXE_SUFFIX.as_ref());
406 if let Some(path) = program_exists(&path) {
409 // It's ok to use `set_extension` here because the intent is to
410 // remove the extension that was just added.
411 path.set_extension("");
412 return path::maybe_verbatim(&path);
415 ensure_no_nuls(exe_path)?;
416 // From the `CreateProcessW` docs:
417 // > If the file name does not contain an extension, .exe is appended.
418 // Note that this rule only applies when searching paths.
419 let has_extension = exe_path.bytes().contains(&b'.');
421 // Search the directories given by `search_paths`.
422 let result = search_paths(parent_paths, child_paths, |mut path| {
423 path.push(&exe_path);
425 path.set_extension(EXE_EXTENSION);
427 program_exists(&path)
429 if let Some(path) = result {
433 // If we get here then the executable cannot be found.
434 Err(io::const_io_error!(io::ErrorKind::NotFound, "program not found"))
437 // Calls `f` for every path that should be used to find an executable.
438 // Returns once `f` returns the path to an executable or all paths have been searched.
439 fn search_paths<Paths, Exists>(
441 child_paths: Option<&OsStr>,
443 ) -> Option<Vec<u16>>
445 Paths: FnOnce() -> Option<OsString>,
446 Exists: FnMut(PathBuf) -> Option<Vec<u16>>,
449 // This is for consistency with Rust's historic behaviour.
450 if let Some(paths) = child_paths {
451 for path in env::split_paths(paths).filter(|p| !p.as_os_str().is_empty()) {
452 if let Some(path) = exists(path) {
458 // 2. Application path
459 if let Ok(mut app_path) = env::current_exe() {
461 if let Some(path) = exists(app_path) {
466 // 3 & 4. System paths
467 // SAFETY: This uses `fill_utf16_buf` to safely call the OS functions.
469 if let Ok(Some(path)) = super::fill_utf16_buf(
470 |buf, size| c::GetSystemDirectoryW(buf, size),
471 |buf| exists(PathBuf::from(OsString::from_wide(buf))),
475 #[cfg(not(target_vendor = "uwp"))]
477 if let Ok(Some(path)) = super::fill_utf16_buf(
478 |buf, size| c::GetWindowsDirectoryW(buf, size),
479 |buf| exists(PathBuf::from(OsString::from_wide(buf))),
487 if let Some(parent_paths) = parent_paths() {
488 for path in env::split_paths(&parent_paths).filter(|p| !p.as_os_str().is_empty()) {
489 if let Some(path) = exists(path) {
497 /// Check if a file exists without following symlinks.
498 fn program_exists(path: &Path) -> Option<Vec<u16>> {
500 let path = path::maybe_verbatim(path).ok()?;
501 // Getting attributes using `GetFileAttributesW` does not follow symlinks
502 // and it will almost always be successful if the link exists.
503 // There are some exceptions for special system files (e.g. the pagefile)
504 // but these are not executable.
505 if c::GetFileAttributesW(path.as_ptr()) == c::INVALID_FILE_ATTRIBUTES {
514 fn to_handle(&self, stdio_id: c::DWORD, pipe: &mut Option<AnonPipe>) -> io::Result<Handle> {
516 // If no stdio handle is available, then inherit means that it
517 // should still be unavailable so propagate the
518 // INVALID_HANDLE_VALUE.
519 Stdio::Inherit => match stdio::get_handle(stdio_id) {
521 let io = Handle::from_raw_handle(io);
522 let ret = io.duplicate(0, true, c::DUPLICATE_SAME_ACCESS);
523 io.into_raw_handle();
526 Err(..) => unsafe { Ok(Handle::from_raw_handle(c::INVALID_HANDLE_VALUE)) },
530 let ours_readable = stdio_id != c::STD_INPUT_HANDLE;
531 let pipes = pipe::anon_pipe(ours_readable, true)?;
532 *pipe = Some(pipes.ours);
533 Ok(pipes.theirs.into_handle())
536 Stdio::Pipe(ref source) => {
537 let ours_readable = stdio_id != c::STD_INPUT_HANDLE;
538 pipe::spawn_pipe_relay(source, ours_readable, true).map(AnonPipe::into_handle)
541 Stdio::Handle(ref handle) => handle.duplicate(0, true, c::DUPLICATE_SAME_ACCESS),
543 // Open up a reference to NUL with appropriate read/write
544 // permissions as well as the ability to be inherited to child
545 // processes (as this is about to be inherited).
547 let size = mem::size_of::<c::SECURITY_ATTRIBUTES>();
548 let mut sa = c::SECURITY_ATTRIBUTES {
549 nLength: size as c::DWORD,
550 lpSecurityDescriptor: ptr::null_mut(),
553 let mut opts = OpenOptions::new();
554 opts.read(stdio_id == c::STD_INPUT_HANDLE);
555 opts.write(stdio_id != c::STD_INPUT_HANDLE);
556 opts.security_attributes(&mut sa);
557 File::open(Path::new("NUL"), &opts).map(|file| file.into_inner())
563 impl From<AnonPipe> for Stdio {
564 fn from(pipe: AnonPipe) -> Stdio {
569 impl From<File> for Stdio {
570 fn from(file: File) -> Stdio {
571 Stdio::Handle(file.into_inner())
575 ////////////////////////////////////////////////////////////////////////////////
577 ////////////////////////////////////////////////////////////////////////////////
579 /// A value representing a child process.
581 /// The lifetime of this value is linked to the lifetime of the actual
582 /// process - the Process destructor calls self.finish() which waits
583 /// for the process to terminate.
586 main_thread_handle: Handle,
590 pub fn kill(&mut self) -> io::Result<()> {
591 cvt(unsafe { c::TerminateProcess(self.handle.as_raw_handle(), 1) })?;
595 pub fn id(&self) -> u32 {
596 unsafe { c::GetProcessId(self.handle.as_raw_handle()) as u32 }
599 pub fn main_thread_handle(&self) -> BorrowedHandle<'_> {
600 self.main_thread_handle.as_handle()
603 pub fn wait(&mut self) -> io::Result<ExitStatus> {
605 let res = c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE);
606 if res != c::WAIT_OBJECT_0 {
607 return Err(Error::last_os_error());
610 cvt(c::GetExitCodeProcess(self.handle.as_raw_handle(), &mut status))?;
611 Ok(ExitStatus(status))
615 pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
617 match c::WaitForSingleObject(self.handle.as_raw_handle(), 0) {
618 c::WAIT_OBJECT_0 => {}
622 _ => return Err(io::Error::last_os_error()),
625 cvt(c::GetExitCodeProcess(self.handle.as_raw_handle(), &mut status))?;
626 Ok(Some(ExitStatus(status)))
630 pub fn handle(&self) -> &Handle {
634 pub fn into_handle(self) -> Handle {
639 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
640 pub struct ExitStatus(c::DWORD);
643 pub fn exit_ok(&self) -> Result<(), ExitStatusError> {
644 match NonZeroDWORD::try_from(self.0) {
645 /* was nonzero */ Ok(failure) => Err(ExitStatusError(failure)),
646 /* was zero, couldn't convert */ Err(_) => Ok(()),
649 pub fn code(&self) -> Option<i32> {
654 /// Converts a raw `c::DWORD` to a type-safe `ExitStatus` by wrapping it without copying.
655 impl From<c::DWORD> for ExitStatus {
656 fn from(u: c::DWORD) -> ExitStatus {
661 impl fmt::Display for ExitStatus {
662 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
663 // Windows exit codes with the high bit set typically mean some form of
664 // unhandled exception or warning. In this scenario printing the exit
665 // code in decimal doesn't always make sense because it's a very large
666 // and somewhat gibberish number. The hex code is a bit more
667 // recognizable and easier to search for, so print that.
668 if self.0 & 0x80000000 != 0 {
669 write!(f, "exit code: {:#x}", self.0)
671 write!(f, "exit code: {}", self.0)
676 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
677 pub struct ExitStatusError(c::NonZeroDWORD);
679 impl Into<ExitStatus> for ExitStatusError {
680 fn into(self) -> ExitStatus {
681 ExitStatus(self.0.into())
685 impl ExitStatusError {
686 pub fn code(self) -> Option<NonZeroI32> {
687 Some((u32::from(self.0) as i32).try_into().unwrap())
691 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
692 pub struct ExitCode(c::DWORD);
695 pub const SUCCESS: ExitCode = ExitCode(EXIT_SUCCESS as _);
696 pub const FAILURE: ExitCode = ExitCode(EXIT_FAILURE as _);
699 pub fn as_i32(&self) -> i32 {
704 impl From<u8> for ExitCode {
705 fn from(code: u8) -> Self {
706 ExitCode(c::DWORD::from(code))
710 impl From<u32> for ExitCode {
711 fn from(code: u32) -> Self {
712 ExitCode(c::DWORD::from(code))
716 fn zeroed_startupinfo() -> c::STARTUPINFO {
719 lpReserved: ptr::null_mut(),
720 lpDesktop: ptr::null_mut(),
721 lpTitle: ptr::null_mut(),
732 lpReserved2: ptr::null_mut(),
733 hStdInput: c::INVALID_HANDLE_VALUE,
734 hStdOutput: c::INVALID_HANDLE_VALUE,
735 hStdError: c::INVALID_HANDLE_VALUE,
739 fn zeroed_process_information() -> c::PROCESS_INFORMATION {
740 c::PROCESS_INFORMATION {
741 hProcess: ptr::null_mut(),
742 hThread: ptr::null_mut(),
748 // Produces a wide string *without terminating null*; returns an error if
749 // `prog` or any of the `args` contain a nul.
750 fn make_command_line(argv0: &OsStr, args: &[Arg], force_quotes: bool) -> io::Result<Vec<u16>> {
751 // Encode the command and arguments in a command line string such
752 // that the spawned process may recover them using CommandLineToArgvW.
753 let mut cmd: Vec<u16> = Vec::new();
755 // Always quote the program name so CreateProcess to avoid ambiguity when
756 // the child process parses its arguments.
757 // Note that quotes aren't escaped here because they can't be used in arg0.
758 // But that's ok because file paths can't contain quotes.
759 cmd.push(b'"' as u16);
760 cmd.extend(argv0.encode_wide());
761 cmd.push(b'"' as u16);
764 cmd.push(' ' as u16);
765 args::append_arg(&mut cmd, arg, force_quotes)?;
770 // Get `cmd.exe` for use with bat scripts, encoded as a UTF-16 string.
771 fn command_prompt() -> io::Result<Vec<u16>> {
772 let mut system: Vec<u16> = super::fill_utf16_buf(
773 |buf, size| unsafe { c::GetSystemDirectoryW(buf, size) },
776 system.extend("\\cmd.exe".encode_utf16().chain([0]));
780 fn make_envp(maybe_env: Option<BTreeMap<EnvKey, OsString>>) -> io::Result<(*mut c_void, Vec<u16>)> {
781 // On Windows we pass an "environment block" which is not a char**, but
782 // rather a concatenation of null-terminated k=v\0 sequences, with a final
784 if let Some(env) = maybe_env {
785 let mut blk = Vec::new();
787 // If there are no environment variables to set then signal this by
794 ensure_no_nuls(k.os_string)?;
796 blk.push('=' as u16);
797 blk.extend(ensure_no_nuls(v)?.encode_wide());
801 Ok((blk.as_mut_ptr() as *mut c_void, blk))
803 Ok((ptr::null_mut(), Vec::new()))
807 fn make_dirp(d: Option<&OsString>) -> io::Result<(*const u16, Vec<u16>)> {
810 let mut dir_str: Vec<u16> = ensure_no_nuls(dir)?.encode_wide().collect();
812 Ok((dir_str.as_ptr(), dir_str))
814 None => Ok((ptr::null(), Vec::new())),
818 pub struct CommandArgs<'a> {
819 iter: crate::slice::Iter<'a, Arg>,
822 impl<'a> Iterator for CommandArgs<'a> {
823 type Item = &'a OsStr;
824 fn next(&mut self) -> Option<&'a OsStr> {
825 self.iter.next().map(|arg| match arg {
826 Arg::Regular(s) | Arg::Raw(s) => s.as_ref(),
829 fn size_hint(&self) -> (usize, Option<usize>) {
830 self.iter.size_hint()
834 impl<'a> ExactSizeIterator for CommandArgs<'a> {
835 fn len(&self) -> usize {
838 fn is_empty(&self) -> bool {
843 impl<'a> fmt::Debug for CommandArgs<'a> {
844 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
845 f.debug_list().entries(self.iter.clone()).finish()