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

   1 //! Unix-specific extensions to primitives in the `std::process` module.
   2
   3 #![stable(feature = "rust1", since = "1.0.0")]
   4
   5 use crate::ffi::OsStr;
   6 use crate::io;
   7 use crate::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
   8 use crate::process;
   9 use crate::sealed::Sealed;
  10 use crate::sys;
  11 use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
  12
  13 /// Unix-specific extensions to the [`process::Command`] builder.
  14 ///
  15 /// This trait is sealed: it cannot be implemented outside the standard library.
  16 /// This is so that future additional methods are not breaking changes.
  17 #[stable(feature = "rust1", since = "1.0.0")]
  18 pub trait CommandExt: Sealed {
  19     /// Sets the child process's user ID. This translates to a
  20     /// `setuid` call in the child process. Failure in the `setuid`
  21     /// call will cause the spawn to fail.
  22     #[stable(feature = "rust1", since = "1.0.0")]
  23     fn uid(
  24         &mut self,
  25         #[cfg(not(target_os = "vxworks"))] id: u32,
  26         #[cfg(target_os = "vxworks")] id: u16,
  27     ) -> &mut process::Command;
  28
  29     /// Similar to `uid`, but sets the group ID of the child process. This has
  30     /// the same semantics as the `uid` field.
  31     #[stable(feature = "rust1", since = "1.0.0")]
  32     fn gid(
  33         &mut self,
  34         #[cfg(not(target_os = "vxworks"))] id: u32,
  35         #[cfg(target_os = "vxworks")] id: u16,
  36     ) -> &mut process::Command;
  37
  38     /// Sets the supplementary group IDs for the calling process. Translates to
  39     /// a `setgroups` call in the child process.
  40     #[unstable(feature = "setgroups", issue = "38527", reason = "")]
  41     fn groups(
  42         &mut self,
  43         #[cfg(not(target_os = "vxworks"))] groups: &[u32],
  44         #[cfg(target_os = "vxworks")] groups: &[u16],
  45     ) -> &mut process::Command;
  46
  47     /// Schedules a closure to be run just before the `exec` function is
  48     /// invoked.
  49     ///
  50     /// The closure is allowed to return an I/O error whose OS error code will
  51     /// be communicated back to the parent and returned as an error from when
  52     /// the spawn was requested.
  53     ///
  54     /// Multiple closures can be registered and they will be called in order of
  55     /// their registration. If a closure returns `Err` then no further closures
  56     /// will be called and the spawn operation will immediately return with a
  57     /// failure.
  58     ///
  59     /// # Notes and Safety
  60     ///
  61     /// This closure will be run in the context of the child process after a
  62     /// `fork`. This primarily means that any modifications made to memory on
  63     /// behalf of this closure will **not** be visible to the parent process.
  64     /// This is often a very constrained environment where normal operations
  65     /// like `malloc`, accessing environment variables through [`std::env`]
  66     /// or acquiring a mutex are not guaranteed to work (due to
  67     /// other threads perhaps still running when the `fork` was run).
  68     ///
  69     /// For further details refer to the [POSIX fork() specification]
  70     /// and the equivalent documentation for any targeted
  71     /// platform, especially the requirements around *async-signal-safety*.
  72     ///
  73     /// This also means that all resources such as file descriptors and
  74     /// memory-mapped regions got duplicated. It is your responsibility to make
  75     /// sure that the closure does not violate library invariants by making
  76     /// invalid use of these duplicates.
  77     ///
  78     /// Panicking in the closure is safe only if all the format arguments for the
  79     /// panic message can be safely formatted; this is because although
  80     /// `Command` calls [`std::panic::always_abort`](crate::panic::always_abort)
  81     /// before calling the pre_exec hook, panic will still try to format the
  82     /// panic message.
  83     ///
  84     /// When this closure is run, aspects such as the stdio file descriptors and
  85     /// working directory have successfully been changed, so output to these
  86     /// locations may not appear where intended.
  87     ///
  88     /// [POSIX fork() specification]:
  89     ///     https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html
  90     /// [`std::env`]: mod@crate::env
  91     #[stable(feature = "process_pre_exec", since = "1.34.0")]
  92     unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
  93     where
  94         F: FnMut() -> io::Result<()> + Send + Sync + 'static;
  95
  96     /// Schedules a closure to be run just before the `exec` function is
  97     /// invoked.
  98     ///
  99     /// This method is stable and usable, but it should be unsafe. To fix
 100     /// that, it got deprecated in favor of the unsafe [`pre_exec`].
 101     ///
 102     /// [`pre_exec`]: CommandExt::pre_exec
 103     #[stable(feature = "process_exec", since = "1.15.0")]
 104     #[rustc_deprecated(since = "1.37.0", reason = "should be unsafe, use `pre_exec` instead")]
 105     fn before_exec<F>(&mut self, f: F) -> &mut process::Command
 106     where
 107         F: FnMut() -> io::Result<()> + Send + Sync + 'static,
 108     {
 109         unsafe { self.pre_exec(f) }
 110     }
 111
 112     /// Performs all the required setup by this `Command`, followed by calling
 113     /// the `execvp` syscall.
 114     ///
 115     /// On success this function will not return, and otherwise it will return
 116     /// an error indicating why the exec (or another part of the setup of the
 117     /// `Command`) failed.
 118     ///
 119     /// `exec` not returning has the same implications as calling
 120     /// [`process::exit`] – no destructors on the current stack or any other
 121     /// thread’s stack will be run. Therefore, it is recommended to only call
 122     /// `exec` at a point where it is fine to not run any destructors. Note,
 123     /// that the `execvp` syscall independently guarantees that all memory is
 124     /// freed and all file descriptors with the `CLOEXEC` option (set by default
 125     /// on all file descriptors opened by the standard library) are closed.
 126     ///
 127     /// This function, unlike `spawn`, will **not** `fork` the process to create
 128     /// a new child. Like spawn, however, the default behavior for the stdio
 129     /// descriptors will be to inherited from the current process.
 130     ///
 131     /// # Notes
 132     ///
 133     /// The process may be in a "broken state" if this function returns in
 134     /// error. For example the working directory, environment variables, signal
 135     /// handling settings, various user/group information, or aspects of stdio
 136     /// file descriptors may have changed. If a "transactional spawn" is
 137     /// required to gracefully handle errors it is recommended to use the
 138     /// cross-platform `spawn` instead.
 139     #[stable(feature = "process_exec2", since = "1.9.0")]
 140     fn exec(&mut self) -> io::Error;
 141
 142     /// Set executable argument
 143     ///
 144     /// Set the first process argument, `argv[0]`, to something other than the
 145     /// default executable path.
 146     #[stable(feature = "process_set_argv0", since = "1.45.0")]
 147     fn arg0<S>(&mut self, arg: S) -> &mut process::Command
 148     where
 149         S: AsRef<OsStr>;
 150 }
 151
 152 #[stable(feature = "rust1", since = "1.0.0")]
 153 impl CommandExt for process::Command {
 154     fn uid(
 155         &mut self,
 156         #[cfg(not(target_os = "vxworks"))] id: u32,
 157         #[cfg(target_os = "vxworks")] id: u16,
 158     ) -> &mut process::Command {
 159         self.as_inner_mut().uid(id);
 160         self
 161     }
 162
 163     fn gid(
 164         &mut self,
 165         #[cfg(not(target_os = "vxworks"))] id: u32,
 166         #[cfg(target_os = "vxworks")] id: u16,
 167     ) -> &mut process::Command {
 168         self.as_inner_mut().gid(id);
 169         self
 170     }
 171
 172     fn groups(
 173         &mut self,
 174         #[cfg(not(target_os = "vxworks"))] groups: &[u32],
 175         #[cfg(target_os = "vxworks")] groups: &[u16],
 176     ) -> &mut process::Command {
 177         self.as_inner_mut().groups(groups);
 178         self
 179     }
 180
 181     unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
 182     where
 183         F: FnMut() -> io::Result<()> + Send + Sync + 'static,
 184     {
 185         self.as_inner_mut().pre_exec(Box::new(f));
 186         self
 187     }
 188
 189     fn exec(&mut self) -> io::Error {
 190         // NOTE: This may *not* be safe to call after `libc::fork`, because it
 191         // may allocate. That may be worth fixing at some point in the future.
 192         self.as_inner_mut().exec(sys::process::Stdio::Inherit)
 193     }
 194
 195     fn arg0<S>(&mut self, arg: S) -> &mut process::Command
 196     where
 197         S: AsRef<OsStr>,
 198     {
 199         self.as_inner_mut().set_arg_0(arg.as_ref());
 200         self
 201     }
 202 }
 203
 204 /// Unix-specific extensions to [`process::ExitStatus`] and
 205 /// [`ExitStatusError`](process::ExitStatusError).
 206 ///
 207 /// On Unix, `ExitStatus` **does not necessarily represent an exit status**, as
 208 /// passed to the `exit` system call or returned by
 209 /// [`ExitStatus::code()`](crate::process::ExitStatus::code).  It represents **any wait status**
 210 /// as returned by one of the `wait` family of system
 211 /// calls.
 212 ///
 213 /// A Unix wait status (a Rust `ExitStatus`) can represent a Unix exit status, but can also
 214 /// represent other kinds of process event.
 215 ///
 216 /// This trait is sealed: it cannot be implemented outside the standard library.
 217 /// This is so that future additional methods are not breaking changes.
 218 #[stable(feature = "rust1", since = "1.0.0")]
 219 pub trait ExitStatusExt: Sealed {
 220     /// Creates a new `ExitStatus` or `ExitStatusError` from the raw underlying integer status
 221     /// value from `wait`
 222     ///
 223     /// The value should be a **wait status, not an exit status**.
 224     ///
 225     /// # Panics
 226     ///
 227     /// Panics on an attempt to make an `ExitStatusError` from a wait status of `0`.
 228     ///
 229     /// Making an `ExitStatus` always succeeds and never panics.
 230     #[stable(feature = "exit_status_from", since = "1.12.0")]
 231     fn from_raw(raw: i32) -> Self;
 232
 233     /// If the process was terminated by a signal, returns that signal.
 234     ///
 235     /// In other words, if `WIFSIGNALED`, this returns `WTERMSIG`.
 236     #[stable(feature = "rust1", since = "1.0.0")]
 237     fn signal(&self) -> Option<i32>;
 238
 239     /// If the process was terminated by a signal, says whether it dumped core.
 240     #[unstable(feature = "unix_process_wait_more", issue = "80695")]
 241     fn core_dumped(&self) -> bool;
 242
 243     /// If the process was stopped by a signal, returns that signal.
 244     ///
 245     /// In other words, if `WIFSTOPPED`, this returns `WSTOPSIG`.  This is only possible if the status came from
 246     /// a `wait` system call which was passed `WUNTRACED`, and was then converted into an `ExitStatus`.
 247     #[unstable(feature = "unix_process_wait_more", issue = "80695")]
 248     fn stopped_signal(&self) -> Option<i32>;
 249
 250     /// Whether the process was continued from a stopped status.
 251     ///
 252     /// Ie, `WIFCONTINUED`.  This is only possible if the status came from a `wait` system call
 253     /// which was passed `WCONTINUED`, and was then converted into an `ExitStatus`.
 254     #[unstable(feature = "unix_process_wait_more", issue = "80695")]
 255     fn continued(&self) -> bool;
 256
 257     /// Returns the underlying raw `wait` status.
 258     ///
 259     /// The returned integer is a **wait status, not an exit status**.
 260     #[unstable(feature = "unix_process_wait_more", issue = "80695")]
 261     fn into_raw(self) -> i32;
 262 }
 263
 264 #[stable(feature = "rust1", since = "1.0.0")]
 265 impl ExitStatusExt for process::ExitStatus {
 266     fn from_raw(raw: i32) -> Self {
 267         process::ExitStatus::from_inner(From::from(raw))
 268     }
 269
 270     fn signal(&self) -> Option<i32> {
 271         self.as_inner().signal()
 272     }
 273
 274     fn core_dumped(&self) -> bool {
 275         self.as_inner().core_dumped()
 276     }
 277
 278     fn stopped_signal(&self) -> Option<i32> {
 279         self.as_inner().stopped_signal()
 280     }
 281
 282     fn continued(&self) -> bool {
 283         self.as_inner().continued()
 284     }
 285
 286     fn into_raw(self) -> i32 {
 287         self.as_inner().into_raw().into()
 288     }
 289 }
 290
 291 #[unstable(feature = "exit_status_error", issue = "84908")]
 292 impl ExitStatusExt for process::ExitStatusError {
 293     fn from_raw(raw: i32) -> Self {
 294         process::ExitStatus::from_raw(raw)
 295             .exit_ok()
 296             .expect_err("<ExitStatusError as ExitStatusExt>::from_raw(0) but zero is not an error")
 297     }
 298
 299     fn signal(&self) -> Option<i32> {
 300         self.into_status().signal()
 301     }
 302
 303     fn core_dumped(&self) -> bool {
 304         self.into_status().core_dumped()
 305     }
 306
 307     fn stopped_signal(&self) -> Option<i32> {
 308         self.into_status().stopped_signal()
 309     }
 310
 311     fn continued(&self) -> bool {
 312         self.into_status().continued()
 313     }
 314
 315     fn into_raw(self) -> i32 {
 316         self.into_status().into_raw()
 317     }
 318 }
 319
 320 #[stable(feature = "process_extensions", since = "1.2.0")]
 321 impl FromRawFd for process::Stdio {
 322     #[inline]
 323     unsafe fn from_raw_fd(fd: RawFd) -> process::Stdio {
 324         let fd = sys::fd::FileDesc::new(fd);
 325         let io = sys::process::Stdio::Fd(fd);
 326         process::Stdio::from_inner(io)
 327     }
 328 }
 329
 330 #[stable(feature = "process_extensions", since = "1.2.0")]
 331 impl AsRawFd for process::ChildStdin {
 332     #[inline]
 333     fn as_raw_fd(&self) -> RawFd {
 334         self.as_inner().fd().raw()
 335     }
 336 }
 337
 338 #[stable(feature = "process_extensions", since = "1.2.0")]
 339 impl AsRawFd for process::ChildStdout {
 340     #[inline]
 341     fn as_raw_fd(&self) -> RawFd {
 342         self.as_inner().fd().raw()
 343     }
 344 }
 345
 346 #[stable(feature = "process_extensions", since = "1.2.0")]
 347 impl AsRawFd for process::ChildStderr {
 348     #[inline]
 349     fn as_raw_fd(&self) -> RawFd {
 350         self.as_inner().fd().raw()
 351     }
 352 }
 353
 354 #[stable(feature = "into_raw_os", since = "1.4.0")]
 355 impl IntoRawFd for process::ChildStdin {
 356     #[inline]
 357     fn into_raw_fd(self) -> RawFd {
 358         self.into_inner().into_fd().into_raw()
 359     }
 360 }
 361
 362 #[stable(feature = "into_raw_os", since = "1.4.0")]
 363 impl IntoRawFd for process::ChildStdout {
 364     #[inline]
 365     fn into_raw_fd(self) -> RawFd {
 366         self.into_inner().into_fd().into_raw()
 367     }
 368 }
 369
 370 #[stable(feature = "into_raw_os", since = "1.4.0")]
 371 impl IntoRawFd for process::ChildStderr {
 372     #[inline]
 373     fn into_raw_fd(self) -> RawFd {
 374         self.into_inner().into_fd().into_raw()
 375     }
 376 }
 377
 378 /// Returns the OS-assigned process identifier associated with this process's parent.
 379 #[stable(feature = "unix_ppid", since = "1.27.0")]
 380 pub fn parent_id() -> u32 {
 381     crate::sys::os::getppid()
 382 }