Struct std::process::Stdio

1.0.0 · source ·

pub struct 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.

Implementations

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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

Run

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();

Run

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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

Run

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

Run

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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);

Run

Trait Implementations

1.16.0 · source

impl Debug for Stdio

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

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"
);

Run

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

Run

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");

Run

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");