# Struct std::process::Command

1.0.0 · source ·

    pub struct Command { /* private fields */ }

Expand description

A process builder, providing fine-grained control over how a new process should be spawned.

A default configuration can be generated using `Command::new(program)`, where `program` gives a path to the program to be executed. Additional builder methods allow the configuration to be changed (for example, by adding arguments) prior to spawning:

    use std::process::Command;

    let output = if cfg!(target_os = "windows") {
        Command::new("cmd")
            .args(["/C", "echo hello"])
            .output()
            .expect("failed to execute process")
    } else {
        Command::new("sh")
            .arg("-c")
            .arg("echo hello")
            .output()
            .expect("failed to execute process")
    };

    let hello = output.stdout;

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`Command` can be reused to spawn multiple processes. The builder methods change the command without needing to immediately spawn the process.

    use std::process::Command;

    let mut echo_hello = Command::new("sh");
    echo_hello.arg("-c").arg("echo hello");
    let hello_1 = echo_hello.output().expect("failed to execute process");
    let hello_2 = echo_hello.output().expect("failed to execute process");

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Similarly, you can call builder methods after spawning a process and then spawn a new process with the modified settings.

    use std::process::Command;

    let mut list_dir = Command::new("ls");

    // Execute `ls` in the current directory of the program.
    list_dir.status().expect("process failed to execute");

    println!();

    // Change `ls` to execute in the root directory.
    list_dir.current_dir("/");

    // And then execute `ls` again but in the root directory.
    list_dir.status().expect("process failed to execute");

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## Implementations§

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### impl Command

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#### pub fn new<S: AsRef<OsStr>>(program: S) -> Command

Constructs a new `Command` for launching the program at path `program`, with the following default configuration:

- No arguments to the program
- Inherit the current process’s environment
- Inherit the current process’s working directory
- Inherit stdin/stdout/stderr for `spawn` or `status`, but create pipes for `output`

Builder methods are provided to change these defaults and otherwise configure the process.

If `program` is not an absolute path, the `PATH` will be searched in an OS-defined way.

The search path to be used may be controlled by setting the `PATH` environment variable on the Command, but this has some implementation limitations on Windows (see issue #37519).

##### Platform-specific behavior

Note on Windows: For executable files with the .exe extension, it can be omitted when specifying the program for this Command. However, if the file has a different extension, a filename including the extension needs to be provided, otherwise the file won’t be found.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("sh")
        .spawn()
        .expect("sh command failed to start");

Run
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#### pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Command

Adds an argument to pass to the program.

Only one argument can be passed per use. So instead of:

    .arg("-C /path/to/repo")

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usage would be:

    .arg("-C")
    .arg("/path/to/repo")

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To pass multiple arguments see `args`.

Note that the argument is not passed through a shell, but given literally to the program. This means that shell syntax like quotes, escaped characters, word splitting, glob patterns, variable substitution, etc. have no effect.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .arg("-l")
        .arg("-a")
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn args<I, S>(&mut self, args: I) -> &mut Command where I: IntoIterator<Item = S>, S: AsRef<OsStr>,

Adds multiple arguments to pass to the program.

To pass a single argument see `arg`.

Note that the arguments are not passed through a shell, but given literally to the program. This means that shell syntax like quotes, escaped characters, word splitting, glob patterns, variable substitution, etc. have no effect.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .args(["-l", "-a"])
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn env<K, V>(&mut self, key: K, val: V) -> &mut Command where K: AsRef<OsStr>, V: AsRef<OsStr>,

Inserts or updates an explicit environment variable mapping.

This method allows you to add an environment variable mapping to the spawned process or overwrite a previously set value. You can use `Command::envs` to set multiple environment variables simultaneously.

Child processes will inherit environment variables from their parent process by default. Environment variables explicitly set using `Command::env` take precedence over inherited variables. You can disable environment variable inheritance entirely using `Command::env_clear` or for a single key using `Command::env_remove`.

Note that environment variable names are case-insensitive (but case-preserving) on Windows and case-sensitive on all other platforms.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .env("PATH", "/bin")
        .spawn()
        .expect("ls command failed to start");

Run
1.19.0 · source

#### pub fn envs<I, K, V>(&mut self, vars: I) -> &mut Command where I: IntoIterator<Item = (K, V)>, K: AsRef<OsStr>, V: AsRef<OsStr>,

Inserts or updates multiple explicit environment variable mappings.

This method allows you to add multiple environment variable mappings to the spawned process or overwrite previously set values. You can use `Command::env` to set a single environment variable.

Child processes will inherit environment variables from their parent process by default. Environment variables explicitly set using `Command::envs` take precedence over inherited variables. You can disable environment variable inheritance entirely using `Command::env_clear` or for a single key using `Command::env_remove`.

Note that environment variable names are case-insensitive (but case-preserving) on Windows and case-sensitive on all other platforms.

##### Examples

Basic usage:

    use std::process::{Command, Stdio};
    use std::env;
    use std::collections::HashMap;

    let filtered_env : HashMap<String, String> =
        env::vars().filter(|&(ref k, _)|
            k == "TERM" || k == "TZ" || k == "LANG" || k == "PATH"
        ).collect();

    Command::new("printenv")
        .stdin(Stdio::null())
        .stdout(Stdio::inherit())
        .env_clear()
        .envs(&filtered_env)
        .spawn()
        .expect("printenv failed to start");

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#### pub fn env_remove<K: AsRef<OsStr>>(&mut self, key: K) -> &mut Command

Removes an explicitly set environment variable and prevents inheriting it from a parent process.

This method will remove the explicit value of an environment variable set via `Command::env` or `Command::envs`. In addition, it will prevent the spawned child process from inheriting that environment variable from its parent process.

After calling `Command::env_remove`, the value associated with its key from `Command::get_envs` will be `None`.

To clear all explicitly set environment variables and disable all environment variable inheritance, you can use `Command::env_clear`.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .env_remove("PATH")
        .spawn()
        .expect("ls command failed to start");

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source

#### pub fn env_clear(&mut self) -> &mut Command

Clears all explicitly set environment variables and prevents inheriting any parent process environment variables.

This method will remove all explicitly added environment variables set via `Command::env` or `Command::envs`. In addition, it will prevent the spawned child process from inheriting any environment variable from its parent process.

After calling `Command::env_clear`, the iterator from `Command::get_envs` will be empty.

You can use `Command::env_remove` to clear a single mapping.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .env_clear()
        .spawn()
        .expect("ls command failed to start");

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#### pub fn current_dir<P: AsRef<Path>>(&mut self, dir: P) -> &mut Command

Sets the working directory for the child process.

##### Platform-specific behavior

If the program path is relative (e.g., `"./script.sh"`), it’s ambiguous whether it should be interpreted relative to the parent’s working directory or relative to `current_dir`. The behavior in this case is platform specific and unstable, and it’s recommended to use `canonicalize` to get an absolute program path instead.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .current_dir("/bin")
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn stdin<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command

Configuration for the child process’s standard input (stdin) handle.

Defaults to `inherit` when used with `spawn` or `status`, and defaults to `piped` when used with `output`.

##### Examples

Basic usage:

    use std::process::{Command, Stdio};

    Command::new("ls")
        .stdin(Stdio::null())
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn stdout<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command

Configuration for the child process’s standard output (stdout) handle.

Defaults to `inherit` when used with `spawn` or `status`, and defaults to `piped` when used with `output`.

##### Examples

Basic usage:

    use std::process::{Command, Stdio};

    Command::new("ls")
        .stdout(Stdio::null())
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn stderr<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command

Configuration for the child process’s standard error (stderr) handle.

Defaults to `inherit` when used with `spawn` or `status`, and defaults to `piped` when used with `output`.

##### Examples

Basic usage:

    use std::process::{Command, Stdio};

    Command::new("ls")
        .stderr(Stdio::null())
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn spawn(&mut self) -> Result<Child>

Executes the command as a child process, returning a handle to it.

By default, stdin, stdout and stderr are inherited from the parent.

##### Examples

Basic usage:

    use std::process::Command;

    Command::new("ls")
        .spawn()
        .expect("ls command failed to start");

Run
source

#### pub fn output(&mut self) -> Result<Output>

Executes the command as a child process, waiting for it to finish and collecting all of its output.

By default, stdout and stderr are captured (and used to provide the resulting output). Stdin is not inherited from the parent and any attempt by the child process to read from the stdin stream will result in the stream immediately closing.

##### Examples

ⓘ

    use std::process::Command;
    use std::io::{self, Write};
    let output = Command::new("/bin/cat")
        .arg("file.txt")
        .output()
        .expect("failed to execute process");

    println!("status: {}", output.status);
    io::stdout().write_all(&output.stdout).unwrap();
    io::stderr().write_all(&output.stderr).unwrap();

    assert!(output.status.success());

Run
source

#### pub fn status(&mut self) -> Result<ExitStatus>

Executes a command as a child process, waiting for it to finish and collecting its status.

By default, stdin, stdout and stderr are inherited from the parent.

##### Examples

ⓘ

    use std::process::Command;

    let status = Command::new("/bin/cat")
        .arg("file.txt")
        .status()
        .expect("failed to execute process");

    println!("process finished with: {status}");

    assert!(status.success());

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1.57.0 · source

#### pub fn get_program(&self) -> &OsStr

Returns the path to the program that was given to `Command::new`.

##### Examples

    use std::process::Command;

    let cmd = Command::new("echo");
    assert_eq!(cmd.get_program(), "echo");

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1.57.0 · source

#### pub fn get_args(&self) -> CommandArgs<'_> ⓘ

Returns an iterator of the arguments that will be passed to the program.

This does not include the path to the program as the first argument; it only includes the arguments specified with `Command::arg` and `Command::args`.

##### Examples

    use std::ffi::OsStr;
    use std::process::Command;

    let mut cmd = Command::new("echo");
    cmd.arg("first").arg("second");
    let args: Vec<&OsStr> = cmd.get_args().collect();
    assert_eq!(args, &["first", "second"]);

Run
1.57.0 · source

#### pub fn get_envs(&self) -> CommandEnvs<'_> ⓘ

Returns an iterator of the environment variables explicitly set for the child process.

Environment variables explicitly set using `Command::env`, `Command::envs`, and `Command::env_remove` can be retrieved with this method.

Note that this output does not include environment variables inherited from the parent process.

Each element is a tuple key/value pair `(&OsStr, Option<&OsStr>)`. A `None` value indicates its key was explicitly removed via `Command::env_remove`. The associated key for the `None` value will no longer inherit from its parent process.

An empty iterator can indicate that no explicit mappings were added or that `Command::env_clear` was called. After calling `Command::env_clear`, the child process will not inherit any environment variables from its parent process.

##### Examples

    use std::ffi::OsStr;
    use std::process::Command;

    let mut cmd = Command::new("ls");
    cmd.env("TERM", "dumb").env_remove("TZ");
    let envs: Vec<(&OsStr, Option<&OsStr>)> = cmd.get_envs().collect();
    assert_eq!(envs, &[
        (OsStr::new("TERM"), Some(OsStr::new("dumb"))),
        (OsStr::new("TZ"), None)
    ]);

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1.57.0 · source

#### pub fn get_current_dir(&self) -> Option<&Path>

Returns the working directory for the child process.

This returns `None` if the working directory will not be changed.

##### Examples

    use std::path::Path;
    use std::process::Command;

    let mut cmd = Command::new("ls");
    assert_eq!(cmd.get_current_dir(), None);
    cmd.current_dir("/bin");
    assert_eq!(cmd.get_current_dir(), Some(Path::new("/bin")));

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## Trait Implementations§

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### impl CommandExt for Command

Available on Unix only.
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#### fn uid(&mut self, id: u32) -> &mut Command

Sets the child process’s user ID. This translates to a `setuid` call in the child process. Failure in the `setuid` call will cause the spawn to fail.
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#### fn gid(&mut self, id: u32) -> &mut Command

Similar to `uid`, but sets the group ID of the child process. This has the same semantics as the `uid` field.
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#### fn groups(&mut self, groups: &[u32]) -> &mut Command

🔬This is a nightly-only experimental API. (`setgroups` #90747)
Sets the supplementary group IDs for the calling process. Translates to a `setgroups` call in the child process.
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#### unsafe fn pre_exec<F>(&mut self, f: F) -> &mut Command where F: FnMut() -> Result<()> + Send + Sync + 'static,

Schedules a closure to be run just before the `exec` function is invoked. Read more
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#### fn exec(&mut self) -> Error

Performs all the required setup by this `Command`, followed by calling the `execvp` syscall. Read more
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#### fn arg0<S>(&mut self, arg: S) -> &mut Command where S: AsRef<OsStr>,

Set executable argument Read more
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#### fn process_group(&mut self, pgroup: i32) -> &mut Command

Sets the process group ID (PGID) of the child process. Equivalent to a `setpgid` call in the child process, but may be more efficient. Read more
1.15.0 · source§

#### fn before_exec<F>(&mut self, f: F) -> &mut Command where F: FnMut() -> Result<()> + Send + Sync + 'static,

👎Deprecated since 1.37.0: should be unsafe, use `pre_exec` instead
Schedules a closure to be run just before the `exec` function is invoked. Read more
1.16.0 · source§

### impl CommandExt for Command

Available on Windows only.
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#### fn creation_flags(&mut self, flags: u32) -> &mut Command

Sets the process creation flags to be passed to `CreateProcess`. Read more
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#### fn force_quotes(&mut self, enabled: bool) -> &mut Command

🔬This is a nightly-only experimental API. (`windows_process_extensions_force_quotes` #82227)
Forces all arguments to be wrapped in quote (`"`) characters. Read more
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#### fn raw_arg<S: AsRef<OsStr>>(&mut self, raw_text: S) -> &mut Command

Append literal text to the command line without any quoting or escaping. Read more
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#### fn async_pipes(&mut self, always_async: bool) -> &mut Command

🔬This is a nightly-only experimental API. (`windows_process_extensions_async_pipes` #98289)
When `process::Command` creates pipes, request that our side is always async. Read more
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#### unsafe fn raw_attribute<T: Copy + Send + Sync + 'static>( &mut self, attribute: usize, value: T ) -> &mut Command

🔬This is a nightly-only experimental API. (`windows_process_extensions_raw_attribute` #114854)
Sets a raw attribute on the command, providing extended configuration options for Windows processes. Read more
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### impl CommandExt for Command

Available on Linux only.
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#### fn create_pidfd(&mut self, val: bool) -> &mut Command

🔬This is a nightly-only experimental API. (`linux_pidfd` #82971)
Sets whether a `PidFd` should be created for the `Child` spawned by this `Command`. By default, no pidfd will be created. Read more
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### impl Debug for Command

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Format the program and arguments of a Command for display. Any non-utf8 data is lossily converted using the utf8 replacement character.

The default format approximates a shell invocation of the program along with its arguments. It does not include most of the other command properties. The output is not guaranteed to work (e.g. due to lack of shell-escaping or differences in path resolution) On some platforms you can use the alternate syntax to show more fields.

Note that the debug implementation is platform-specific.

## Auto Trait Implementations§

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### impl !RefUnwindSafe for Command

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### impl Send for Command

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### impl Sync for Command

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### impl Unpin for Command

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### impl !UnwindSafe for Command

## Blanket Implementations§

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### impl<T> Any for Twhere T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for Twhere T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for Twhere T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for Twhere U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.