Stdio in std::process - Rust
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`.

## Stdio

# Struct Stdio

1.0.0 · Source

    pub struct Stdio(/* private fields */);

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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### impl Stdio

1.0.0 · Source

#### 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.

1.0.0 · Source

#### 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()?;

    print!("You piped in the reverse of: ");
    io::stdout().write_all(&output.stdout)?;

1.0.0 · Source

#### 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

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")?;

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

    assert_eq!(reverse.stdout, b"!dlrow ,olleH");

1.87.0 · Source§

### impl From<PipeReader> for Stdio

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#### fn from(pipe: PipeReader) -> Self

Converts to this type from the input type.
1.87.0 · Source§

### impl From<PipeWriter> for Stdio

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#### fn from(pipe: PipeWriter) -> Self

Converts to this type from the input type.
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());

## 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.