Struct tracing_core::stdlib::process::Stdio

1.0.0 · source ·
pub struct Stdio(Stdio);
Expand description

Describes what to do with a standard I/O stream for a child process when passed to the stdin, stdout, and stderr methods of Command.

Tuple Fields§

§0: Stdio

Implementations§

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impl Stdio

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pub fn piped() -> Stdio

A new pipe should be arranged to connect the parent and child processes.

§Examples

With stdout:

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

let output = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::piped())
    .output()
    .expect("Failed to execute command");

assert_eq!(String::from_utf8_lossy(&output.stdout), "Hello, world!\n");
// Nothing echoed to console

With stdin:

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

let mut child = Command::new("rev")
    .stdin(Stdio::piped())
    .stdout(Stdio::piped())
    .spawn()
    .expect("Failed to spawn child process");

let mut stdin = child.stdin.take().expect("Failed to open stdin");
std::thread::spawn(move || {
    stdin.write_all("Hello, world!".as_bytes()).expect("Failed to write to stdin");
});

let output = child.wait_with_output().expect("Failed to read stdout");
assert_eq!(String::from_utf8_lossy(&output.stdout), "!dlrow ,olleH");

Writing more than a pipe buffer’s worth of input to stdin without also reading stdout and stderr at the same time may cause a deadlock. This is an issue when running any program that doesn’t guarantee that it reads its entire stdin before writing more than a pipe buffer’s worth of output. The size of a pipe buffer varies on different targets.

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pub fn inherit() -> Stdio

The child inherits from the corresponding parent descriptor.

§Examples

With stdout:

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

let output = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::inherit())
    .output()
    .expect("Failed to execute command");

assert_eq!(String::from_utf8_lossy(&output.stdout), "");
// "Hello, world!" echoed to console

With stdin:

use std::process::{Command, Stdio};
use std::io::{self, Write};

let output = Command::new("rev")
    .stdin(Stdio::inherit())
    .stdout(Stdio::piped())
    .output()
    .expect("Failed to execute command");

print!("You piped in the reverse of: ");
io::stdout().write_all(&output.stdout).unwrap();
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pub fn null() -> Stdio

This stream will be ignored. This is the equivalent of attaching the stream to /dev/null.

§Examples

With stdout:

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

let output = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::null())
    .output()
    .expect("Failed to execute command");

assert_eq!(String::from_utf8_lossy(&output.stdout), "");
// Nothing echoed to console

With stdin:

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

let output = Command::new("rev")
    .stdin(Stdio::null())
    .stdout(Stdio::piped())
    .output()
    .expect("Failed to execute command");

assert_eq!(String::from_utf8_lossy(&output.stdout), "");
// Ignores any piped-in input
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pub fn makes_pipe(&self) -> bool

🔬This is a nightly-only experimental API. (stdio_makes_pipe #98288)

Returns true if this requires Command to create a new pipe.

§Example
#![feature(stdio_makes_pipe)]
use std::process::Stdio;

let io = Stdio::piped();
assert_eq!(io.makes_pipe(), true);

Trait Implementations§

1.16.0 · source§

impl Debug for Stdio

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

Formats the value using the given formatter. Read more
1.20.0 · source§

impl From<ChildStderr> for Stdio

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fn from(child: ChildStderr) -> Stdio

Converts a ChildStderr into a Stdio.

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

let reverse = Command::new("rev")
    .arg("non_existing_file.txt")
    .stderr(Stdio::piped())
    .spawn()
    .expect("failed reverse command");

let cat = Command::new("cat")
    .arg("-")
    .stdin(reverse.stderr.unwrap()) // Converted into a Stdio here
    .output()
    .expect("failed echo command");

assert_eq!(
    String::from_utf8_lossy(&cat.stdout),
    "rev: cannot open non_existing_file.txt: No such file or directory\n"
);
1.20.0 · source§

impl From<ChildStdin> for Stdio

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fn from(child: ChildStdin) -> Stdio

Converts a ChildStdin into a Stdio.

§Examples

ChildStdin will be converted to Stdio using Stdio::from under the hood.

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

let reverse = Command::new("rev")
    .stdin(Stdio::piped())
    .spawn()
    .expect("failed reverse command");

let _echo = Command::new("echo")
    .arg("Hello, world!")
    .stdout(reverse.stdin.unwrap()) // Converted into a Stdio here
    .output()
    .expect("failed echo command");

// "!dlrow ,olleH" echoed to console
1.20.0 · source§

impl From<ChildStdout> for Stdio

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fn from(child: ChildStdout) -> Stdio

Converts a ChildStdout into a Stdio.

§Examples

ChildStdout will be converted to Stdio using Stdio::from under the hood.

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

let hello = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::piped())
    .spawn()
    .expect("failed echo command");

let reverse = Command::new("rev")
    .stdin(hello.stdout.unwrap())  // Converted into a Stdio here
    .output()
    .expect("failed reverse command");

assert_eq!(reverse.stdout, b"!dlrow ,olleH\n");
1.20.0 · source§

impl From<File> for Stdio

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fn from(file: File) -> Stdio

Converts a File into a Stdio.

§Examples

File will be converted to Stdio using Stdio::from under the hood.

use std::fs::File;
use std::process::Command;

// With the `foo.txt` file containing "Hello, world!"
let file = File::open("foo.txt").unwrap();

let reverse = Command::new("rev")
    .stdin(file)  // Implicit File conversion into a Stdio
    .output()
    .expect("failed reverse command");

assert_eq!(reverse.stdout, b"!dlrow ,olleH");
1.63.0 · source§

impl From<OwnedFd> for Stdio

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fn from(fd: OwnedFd) -> Stdio

Takes ownership of a file descriptor and returns a Stdio that can attach a stream to it.

1.74.0 · source§

impl From<Stderr> for Stdio

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fn from(inherit: Stderr) -> Stdio

Redirect command stdout/stderr to our stderr

§Examples
#![feature(exit_status_error)]
use std::io;
use std::process::Command;

let output = Command::new("whoami")
    .stdout(io::stderr())
    .output()?;
output.status.exit_ok()?;
assert!(output.stdout.is_empty());
1.74.0 · source§

impl From<Stdout> for Stdio

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fn from(inherit: Stdout) -> Stdio

Redirect command stdout/stderr to our stdout

§Examples
#![feature(exit_status_error)]
use std::io;
use std::process::Command;

let output = Command::new("whoami")
    .stdout(io::stdout())
    .output()?;
output.status.exit_ok()?;
assert!(output.stdout.is_empty());
1.2.0 · source§

impl FromRawFd for Stdio

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unsafe fn from_raw_fd(fd: i32) -> Stdio

Constructs a new instance of Self from the given raw file descriptor. Read more

Auto Trait Implementations§

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impl Freeze for Stdio

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impl RefUnwindSafe for Stdio

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impl Send for Stdio

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impl Sync for Stdio

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impl Unpin for Stdio

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impl UnwindSafe for Stdio

Blanket Implementations§

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impl<T> Any for T
where 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 T
where 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 T
where 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 T
where 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 T
where 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 T
where 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.