library/std/src/os/unix/process.rs

   1 //! Unix-specific extensions to primitives in the [`std::process`] module.
   2 //!
   3 //! [`std::process`]: crate::process
   4
   5 #![stable(feature = "rust1", since = "1.0.0")]
   6
   7 use crate::ffi::OsStr;
   8 use crate::io;
   9 use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
  10 use crate::process;
  11 use crate::sealed::Sealed;
  12 use crate::sys;
  13 use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
  14
  15 /// Unix-specific extensions to the [`process::Command`] builder.
  16 ///
  17 /// This trait is sealed: it cannot be implemented outside the standard library.
  18 /// This is so that future additional methods are not breaking changes.
  19 #[stable(feature = "rust1", since = "1.0.0")]
  20 pub trait CommandExt: Sealed {
  21     /// Sets the child process's user ID. This translates to a
  22     /// `setuid` call in the child process. Failure in the `setuid`
  23     /// call will cause the spawn to fail.
  24     #[stable(feature = "rust1", since = "1.0.0")]
  25     fn uid(
  26         &mut self,
  27         #[cfg(not(target_os = "vxworks"))] id: u32,
  28         #[cfg(target_os = "vxworks")] id: u16,
  29     ) -> &mut process::Command;
  30
  31     /// Similar to `uid`, but sets the group ID of the child process. This has
  32     /// the same semantics as the `uid` field.
  33     #[stable(feature = "rust1", since = "1.0.0")]
  34     fn gid(
  35         &mut self,
  36         #[cfg(not(target_os = "vxworks"))] id: u32,
  37         #[cfg(target_os = "vxworks")] id: u16,
  38     ) -> &mut process::Command;
  39
  40     /// Sets the supplementary group IDs for the calling process. Translates to
  41     /// a `setgroups` call in the child process.
  42     #[unstable(feature = "setgroups", issue = "90747")]
  43     fn groups(
  44         &mut self,
  45         #[cfg(not(target_os = "vxworks"))] groups: &[u32],
  46         #[cfg(target_os = "vxworks")] groups: &[u16],
  47     ) -> &mut process::Command;
  48
  49     /// Schedules a closure to be run just before the `exec` function is
  50     /// invoked.
  51     ///
  52     /// The closure is allowed to return an I/O error whose OS error code will
  53     /// be communicated back to the parent and returned as an error from when
  54     /// the spawn was requested.
  55     ///
  56     /// Multiple closures can be registered and they will be called in order of
  57     /// their registration. If a closure returns `Err` then no further closures
  58     /// will be called and the spawn operation will immediately return with a
  59     /// failure.
  60     ///
  61     /// # Notes and Safety
  62     ///
  63     /// This closure will be run in the context of the child process after a
  64     /// `fork`. This primarily means that any modifications made to memory on
  65     /// behalf of this closure will **not** be visible to the parent process.
  66     /// This is often a very constrained environment where normal operations
  67     /// like `malloc`, accessing environment variables through [`std::env`]
  68     /// or acquiring a mutex are not guaranteed to work (due to
  69     /// other threads perhaps still running when the `fork` was run).
  70     ///
  71     /// For further details refer to the [POSIX fork() specification]
  72     /// and the equivalent documentation for any targeted
  73     /// platform, especially the requirements around *async-signal-safety*.
  74     ///
  75     /// This also means that all resources such as file descriptors and
  76     /// memory-mapped regions got duplicated. It is your responsibility to make
  77     /// sure that the closure does not violate library invariants by making
  78     /// invalid use of these duplicates.
  79     ///
  80     /// Panicking in the closure is safe only if all the format arguments for the
  81     /// panic message can be safely formatted; this is because although
  82     /// `Command` calls [`std::panic::always_abort`](crate::panic::always_abort)
  83     /// before calling the pre_exec hook, panic will still try to format the
  84     /// panic message.
  85     ///
  86     /// When this closure is run, aspects such as the stdio file descriptors and
  87     /// working directory have successfully been changed, so output to these
  88     /// locations might not appear where intended.
  89     ///
  90     /// [POSIX fork() specification]:
  91     ///     https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html
  92     /// [`std::env`]: mod@crate::env
  93     #[stable(feature = "process_pre_exec", since = "1.34.0")]
  94     unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
  95     where
  96         F: FnMut() -> io::Result<()> + Send + Sync + 'static;
  97
  98     /// Schedules a closure to be run just before the `exec` function is
  99     /// invoked.
 100     ///
 101     /// This method is stable and usable, but it should be unsafe. To fix
 102     /// that, it got deprecated in favor of the unsafe [`pre_exec`].
 103     ///
 104     /// [`pre_exec`]: CommandExt::pre_exec
 105     #[stable(feature = "process_exec", since = "1.15.0")]
 106     #[rustc_deprecated(since = "1.37.0", reason = "should be unsafe, use `pre_exec` instead")]
 107     fn before_exec<F>(&mut self, f: F) -> &mut process::Command
 108     where
 109         F: FnMut() -> io::Result<()> + Send + Sync + 'static,
 110     {
 111         unsafe { self.pre_exec(f) }
 112     }
 113
 114     /// Performs all the required setup by this `Command`, followed by calling
 115     /// the `execvp` syscall.
 116     ///
 117     /// On success this function will not return, and otherwise it will return
 118     /// an error indicating why the exec (or another part of the setup of the
 119     /// `Command`) failed.
 120     ///
 121     /// `exec` not returning has the same implications as calling
 122     /// [`process::exit`] – no destructors on the current stack or any other
 123     /// thread’s stack will be run. Therefore, it is recommended to only call
 124     /// `exec` at a point where it is fine to not run any destructors. Note,
 125     /// that the `execvp` syscall independently guarantees that all memory is
 126     /// freed and all file descriptors with the `CLOEXEC` option (set by default
 127     /// on all file descriptors opened by the standard library) are closed.
 128     ///
 129     /// This function, unlike `spawn`, will **not** `fork` the process to create
 130     /// a new child. Like spawn, however, the default behavior for the stdio
 131     /// descriptors will be to inherited from the current process.
 132     ///
 133     /// # Notes
 134     ///
 135     /// The process may be in a "broken state" if this function returns in
 136     /// error. For example the working directory, environment variables, signal
 137     /// handling settings, various user/group information, or aspects of stdio
 138     /// file descriptors may have changed. If a "transactional spawn" is
 139     /// required to gracefully handle errors it is recommended to use the
 140     /// cross-platform `spawn` instead.
 141     #[stable(feature = "process_exec2", since = "1.9.0")]
 142     fn exec(&mut self) -> io::Error;
 143
 144     /// Set executable argument
 145     ///
 146     /// Set the first process argument, `argv[0]`, to something other than the
 147     /// default executable path.
 148     #[stable(feature = "process_set_argv0", since = "1.45.0")]
 149     fn arg0<S>(&mut self, arg: S) -> &mut process::Command
 150     where
 151         S: AsRef<OsStr>;
 152 }
 153
 154 #[stable(feature = "rust1", since = "1.0.0")]
 155 impl CommandExt for process::Command {
 156     fn uid(
 157         &mut self,
 158         #[cfg(not(target_os = "vxworks"))] id: u32,
 159         #[cfg(target_os = "vxworks")] id: u16,
 160     ) -> &mut process::Command {
 161         self.as_inner_mut().uid(id);
 162         self
 163     }
 164
 165     fn gid(
 166         &mut self,
 167         #[cfg(not(target_os = "vxworks"))] id: u32,
 168         #[cfg(target_os = "vxworks")] id: u16,
 169     ) -> &mut process::Command {
 170         self.as_inner_mut().gid(id);
 171         self
 172     }
 173
 174     fn groups(
 175         &mut self,
 176         #[cfg(not(target_os = "vxworks"))] groups: &[u32],
 177         #[cfg(target_os = "vxworks")] groups: &[u16],
 178     ) -> &mut process::Command {
 179         self.as_inner_mut().groups(groups);
 180         self
 181     }
 182
 183     unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
 184     where
 185         F: FnMut() -> io::Result<()> + Send + Sync + 'static,
 186     {
 187         self.as_inner_mut().pre_exec(Box::new(f));
 188         self
 189     }
 190
 191     fn exec(&mut self) -> io::Error {
 192         // NOTE: This may *not* be safe to call after `libc::fork`, because it
 193         // may allocate. That may be worth fixing at some point in the future.
 194         self.as_inner_mut().exec(sys::process::Stdio::Inherit)
 195     }
 196
 197     fn arg0<S>(&mut self, arg: S) -> &mut process::Command
 198     where
 199         S: AsRef<OsStr>,
 200     {
 201         self.as_inner_mut().set_arg_0(arg.as_ref());
 202         self
 203     }
 204 }
 205
 206 /// Unix-specific extensions to [`process::ExitStatus`] and
 207 /// [`ExitStatusError`](process::ExitStatusError).
 208 ///
 209 /// On Unix, `ExitStatus` **does not necessarily represent an exit status**, as
 210 /// passed to the `_exit` system call or returned by
 211 /// [`ExitStatus::code()`](crate::process::ExitStatus::code).  It represents **any wait status**
 212 /// as returned by one of the `wait` family of system
 213 /// calls.
 214 ///
 215 /// A Unix wait status (a Rust `ExitStatus`) can represent a Unix exit status, but can also
 216 /// represent other kinds of process event.
 217 ///
 218 /// This trait is sealed: it cannot be implemented outside the standard library.
 219 /// This is so that future additional methods are not breaking changes.
 220 #[stable(feature = "rust1", since = "1.0.0")]
 221 pub trait ExitStatusExt: Sealed {
 222     /// Creates a new `ExitStatus` or `ExitStatusError` from the raw underlying integer status
 223     /// value from `wait`
 224     ///
 225     /// The value should be a **wait status, not an exit status**.
 226     ///
 227     /// # Panics
 228     ///
 229     /// Panics on an attempt to make an `ExitStatusError` from a wait status of `0`.
 230     ///
 231     /// Making an `ExitStatus` always succeeds and never panics.
 232     #[stable(feature = "exit_status_from", since = "1.12.0")]
 233     fn from_raw(raw: i32) -> Self;
 234
 235     /// If the process was terminated by a signal, returns that signal.
 236     ///
 237     /// In other words, if `WIFSIGNALED`, this returns `WTERMSIG`.
 238     #[stable(feature = "rust1", since = "1.0.0")]
 239     fn signal(&self) -> Option<i32>;
 240
 241     /// If the process was terminated by a signal, says whether it dumped core.
 242     #[stable(feature = "unix_process_wait_more", since = "1.58.0")]
 243     fn core_dumped(&self) -> bool;
 244
 245     /// If the process was stopped by a signal, returns that signal.
 246     ///
 247     /// In other words, if `WIFSTOPPED`, this returns `WSTOPSIG`.  This is only possible if the status came from
 248     /// a `wait` system call which was passed `WUNTRACED`, and was then converted into an `ExitStatus`.
 249     #[stable(feature = "unix_process_wait_more", since = "1.58.0")]
 250     fn stopped_signal(&self) -> Option<i32>;
 251
 252     /// Whether the process was continued from a stopped status.
 253     ///
 254     /// Ie, `WIFCONTINUED`.  This is only possible if the status came from a `wait` system call
 255     /// which was passed `WCONTINUED`, and was then converted into an `ExitStatus`.
 256     #[stable(feature = "unix_process_wait_more", since = "1.58.0")]
 257     fn continued(&self) -> bool;
 258
 259     /// Returns the underlying raw `wait` status.
 260     ///
 261     /// The returned integer is a **wait status, not an exit status**.
 262     #[stable(feature = "unix_process_wait_more", since = "1.58.0")]
 263     fn into_raw(self) -> i32;
 264 }
 265
 266 #[stable(feature = "rust1", since = "1.0.0")]
 267 impl ExitStatusExt for process::ExitStatus {
 268     fn from_raw(raw: i32) -> Self {
 269         process::ExitStatus::from_inner(From::from(raw))
 270     }
 271
 272     fn signal(&self) -> Option<i32> {
 273         self.as_inner().signal()
 274     }
 275
 276     fn core_dumped(&self) -> bool {
 277         self.as_inner().core_dumped()
 278     }
 279
 280     fn stopped_signal(&self) -> Option<i32> {
 281         self.as_inner().stopped_signal()
 282     }
 283
 284     fn continued(&self) -> bool {
 285         self.as_inner().continued()
 286     }
 287
 288     fn into_raw(self) -> i32 {
 289         self.as_inner().into_raw().into()
 290     }
 291 }
 292
 293 #[unstable(feature = "exit_status_error", issue = "84908")]
 294 impl ExitStatusExt for process::ExitStatusError {
 295     fn from_raw(raw: i32) -> Self {
 296         process::ExitStatus::from_raw(raw)
 297             .exit_ok()
 298             .expect_err("<ExitStatusError as ExitStatusExt>::from_raw(0) but zero is not an error")
 299     }
 300
 301     fn signal(&self) -> Option<i32> {
 302         self.into_status().signal()
 303     }
 304
 305     fn core_dumped(&self) -> bool {
 306         self.into_status().core_dumped()
 307     }
 308
 309     fn stopped_signal(&self) -> Option<i32> {
 310         self.into_status().stopped_signal()
 311     }
 312
 313     fn continued(&self) -> bool {
 314         self.into_status().continued()
 315     }
 316
 317     fn into_raw(self) -> i32 {
 318         self.into_status().into_raw()
 319     }
 320 }
 321
 322 #[stable(feature = "process_extensions", since = "1.2.0")]
 323 impl FromRawFd for process::Stdio {
 324     #[inline]
 325     unsafe fn from_raw_fd(fd: RawFd) -> process::Stdio {
 326         let fd = sys::fd::FileDesc::from_raw_fd(fd);
 327         let io = sys::process::Stdio::Fd(fd);
 328         process::Stdio::from_inner(io)
 329     }
 330 }
 331
 332 #[unstable(feature = "io_safety", issue = "87074")]
 333 impl From<OwnedFd> for process::Stdio {
 334     #[inline]
 335     fn from(fd: OwnedFd) -> process::Stdio {
 336         let fd = sys::fd::FileDesc::from_inner(fd);
 337         let io = sys::process::Stdio::Fd(fd);
 338         process::Stdio::from_inner(io)
 339     }
 340 }
 341
 342 #[stable(feature = "process_extensions", since = "1.2.0")]
 343 impl AsRawFd for process::ChildStdin {
 344     #[inline]
 345     fn as_raw_fd(&self) -> RawFd {
 346         self.as_inner().as_raw_fd()
 347     }
 348 }
 349
 350 #[stable(feature = "process_extensions", since = "1.2.0")]
 351 impl AsRawFd for process::ChildStdout {
 352     #[inline]
 353     fn as_raw_fd(&self) -> RawFd {
 354         self.as_inner().as_raw_fd()
 355     }
 356 }
 357
 358 #[stable(feature = "process_extensions", since = "1.2.0")]
 359 impl AsRawFd for process::ChildStderr {
 360     #[inline]
 361     fn as_raw_fd(&self) -> RawFd {
 362         self.as_inner().as_raw_fd()
 363     }
 364 }
 365
 366 #[stable(feature = "into_raw_os", since = "1.4.0")]
 367 impl IntoRawFd for process::ChildStdin {
 368     #[inline]
 369     fn into_raw_fd(self) -> RawFd {
 370         self.into_inner().into_inner().into_raw_fd()
 371     }
 372 }
 373
 374 #[stable(feature = "into_raw_os", since = "1.4.0")]
 375 impl IntoRawFd for process::ChildStdout {
 376     #[inline]
 377     fn into_raw_fd(self) -> RawFd {
 378         self.into_inner().into_inner().into_raw_fd()
 379     }
 380 }
 381
 382 #[stable(feature = "into_raw_os", since = "1.4.0")]
 383 impl IntoRawFd for process::ChildStderr {
 384     #[inline]
 385     fn into_raw_fd(self) -> RawFd {
 386         self.into_inner().into_inner().into_raw_fd()
 387     }
 388 }
 389
 390 #[unstable(feature = "io_safety", issue = "87074")]
 391 impl AsFd for crate::process::ChildStdin {
 392     #[inline]
 393     fn as_fd(&self) -> BorrowedFd<'_> {
 394         self.as_inner().as_fd()
 395     }
 396 }
 397
 398 #[unstable(feature = "io_safety", issue = "87074")]
 399 impl From<crate::process::ChildStdin> for OwnedFd {
 400     #[inline]
 401     fn from(child_stdin: crate::process::ChildStdin) -> OwnedFd {
 402         child_stdin.into_inner().into_inner().into_inner()
 403     }
 404 }
 405
 406 #[unstable(feature = "io_safety", issue = "87074")]
 407 impl AsFd for crate::process::ChildStdout {
 408     #[inline]
 409     fn as_fd(&self) -> BorrowedFd<'_> {
 410         self.as_inner().as_fd()
 411     }
 412 }
 413
 414 #[unstable(feature = "io_safety", issue = "87074")]
 415 impl From<crate::process::ChildStdout> for OwnedFd {
 416     #[inline]
 417     fn from(child_stdout: crate::process::ChildStdout) -> OwnedFd {
 418         child_stdout.into_inner().into_inner().into_inner()
 419     }
 420 }
 421
 422 #[unstable(feature = "io_safety", issue = "87074")]
 423 impl AsFd for crate::process::ChildStderr {
 424     #[inline]
 425     fn as_fd(&self) -> BorrowedFd<'_> {
 426         self.as_inner().as_fd()
 427     }
 428 }
 429
 430 #[unstable(feature = "io_safety", issue = "87074")]
 431 impl From<crate::process::ChildStderr> for OwnedFd {
 432     #[inline]
 433     fn from(child_stderr: crate::process::ChildStderr) -> OwnedFd {
 434         child_stderr.into_inner().into_inner().into_inner()
 435     }
 436 }
 437
 438 /// Returns the OS-assigned process identifier associated with this process's parent.
 439 #[must_use]
 440 #[stable(feature = "unix_ppid", since = "1.27.0")]
 441 pub fn parent_id() -> u32 {
 442     crate::sys::os::getppid()
 443 }