Stdin in std::io - Rust
Description: A handle to the standard input stream of a process.

## Stdin

# Struct Stdin

1.0.0 · Source

    pub struct Stdin { /* private fields */ }

Expand description

A handle to the standard input stream of a process.

Each handle is a shared reference to a global buffer of input data to this process. A handle can be `lock`’d to gain full access to `BufRead` methods (e.g., `.lines()`). Reads to this handle are otherwise locked with respect to other reads.

This handle implements the `Read` trait, but beware that concurrent reads of `Stdin` must be executed with care.

Created by the `io::stdin` method.

#### §Note: Windows Portability Considerations

When operating in a console, the Windows implementation of this stream does not support non-UTF-8 byte sequences. Attempting to read bytes that are not valid UTF-8 will return an error.

In a process with a detached console, such as one using `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process, the contained handle will be null. In such cases, the standard library’s `Read` and `Write` will do nothing and silently succeed. All other I/O operations, via the standard library or via raw Windows API calls, will fail.

## §Examples

    use std::io;

    fn main() -> io::Result<()> {
        let mut buffer = String::new();
        let stdin = io::stdin(); // We get `Stdin` here.
        stdin.read_line(&mut buffer)?;
        Ok(())
    }

## Implementations§

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### impl Stdin

1.0.0 · Source

#### pub fn lock(&self) -> StdinLock<'static> ⓘ

Locks this handle to the standard input stream, returning a readable guard.

The lock is released when the returned lock goes out of scope. The returned guard also implements the `Read` and `BufRead` traits for accessing the underlying data.

##### §Examples

    use std::io::{self, BufRead};

    fn main() -> io::Result<()> {
        let mut buffer = String::new();
        let stdin = io::stdin();
        let mut handle = stdin.lock();

        handle.read_line(&mut buffer)?;
        Ok(())
    }

1.0.0 · Source

#### pub fn read_line(&self, buf: &mut String) -> Result<usize>

Locks this handle and reads a line of input, appending it to the specified buffer.

For detailed semantics of this method, see the documentation on `BufRead::read_line`. In particular:

- Previous content of the buffer will be preserved. To avoid appending to the buffer, you need to `clear` it first.
- The trailing newline character, if any, is included in the buffer.

##### §Examples

    use std::io;

    let mut input = String::new();
    match io::stdin().read_line(&mut input) {
        Ok(n) => {
            println!("{n} bytes read");
            println!("{input}");
        }
        Err(error) => println!("error: {error}"),
    }

You can run the example one of two ways:

- Pipe some text to it, e.g., `printf foo | path/to/executable`
- Give it text interactively by running the executable directly, in which case it will wait for the Enter key to be pressed before continuing

1.62.0 · Source

#### pub fn lines(self) -> Lines<StdinLock<'static>> ⓘ

Consumes this handle and returns an iterator over input lines.

For detailed semantics of this method, see the documentation on `BufRead::lines`.

##### §Examples

    use std::io;

    let lines = io::stdin().lines();
    for line in lines {
        println!("got a line: {}", line.unwrap());
    }

## Trait Implementations§

1.63.0 · Source§

### impl AsFd for Stdin

Available on Unix or HermitCore or `target_os=trusty` or WASI or `target_os=motor` only.
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#### fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor. Read more
1.21.0 · Source§

### impl AsRawFd for Stdin

Available on (Unix or HermitCore or `target_os=trusty` or WASI or `target_os=motor`) and non-`target_os=trusty` only.
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#### fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor. Read more
1.16.0 · Source§

### impl Debug for Stdin

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

Formats the value using the given formatter. Read more
1.70.0 · Source§

### impl IsTerminal for Stdin

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#### fn is_terminal(&self) -> bool

Returns `true` if the descriptor/handle refers to a terminal/tty. Read more
1.78.0 · Source§

### impl Read for &Stdin

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#### fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
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#### fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (`read_buf` #78485)
Pull some bytes from this source into the specified buffer. Read more
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#### fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

Like `read`, except that it reads into a slice of buffers. Read more
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#### fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (`can_vector` #69941)
Determines if this `Read`er has an efficient `read_vectored` implementation. Read more
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#### fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>

Reads all bytes until EOF in this source, placing them into `buf`. Read more
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#### fn read_to_string(&mut self, buf: &mut String) -> Result<usize>

Reads all bytes until EOF in this source, appending them to `buf`. Read more
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#### fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>

Reads the exact number of bytes required to fill `buf`. Read more
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#### fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (`read_buf` #78485)
Reads the exact number of bytes required to fill `cursor`. Read more
1.0.0 · Source§

#### fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adapter for this instance of `Read`. Read more
1.0.0 · Source§

#### fn bytes(self) -> Bytes<Self> ⓘ
where Self: Sized,

Transforms this `Read` instance to an `Iterator` over its bytes. Read more
1.0.0 · Source§

#### fn chain<R: Read>(self, next: R) -> Chain<Self, R> ⓘ
where Self: Sized,

Creates an adapter which will chain this stream with another. Read more
1.0.0 · Source§

#### fn take(self, limit: u64) -> Take<Self> ⓘ
where Self: Sized,

Creates an adapter which will read at most `limit` bytes from it. Read more
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#### fn read_array<const N: usize>(&mut self) -> Result<[u8; N]>
where Self: Sized,

🔬This is a nightly-only experimental API. (`read_array` #148848)
Read and return a fixed array of bytes from this source. Read more
1.0.0 · Source§

### impl Read for Stdin

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#### fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
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#### fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (`read_buf` #78485)
Pull some bytes from this source into the specified buffer. Read more
Source§

#### fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

Like `read`, except that it reads into a slice of buffers. Read more
Source§

#### fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (`can_vector` #69941)
Determines if this `Read`er has an efficient `read_vectored` implementation. Read more
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#### fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>

Reads all bytes until EOF in this source, placing them into `buf`. Read more
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#### fn read_to_string(&mut self, buf: &mut String) -> Result<usize>

Reads all bytes until EOF in this source, appending them to `buf`. Read more
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#### fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>

Reads the exact number of bytes required to fill `buf`. Read more
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#### fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (`read_buf` #78485)
Reads the exact number of bytes required to fill `cursor`. Read more
1.0.0 · Source§

#### fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adapter for this instance of `Read`. Read more
1.0.0 · Source§

#### fn bytes(self) -> Bytes<Self> ⓘ
where Self: Sized,

Transforms this `Read` instance to an `Iterator` over its bytes. Read more
1.0.0 · Source§

#### fn chain<R: Read>(self, next: R) -> Chain<Self, R> ⓘ
where Self: Sized,

Creates an adapter which will chain this stream with another. Read more
1.0.0 · Source§

#### fn take(self, limit: u64) -> Take<Self> ⓘ
where Self: Sized,

Creates an adapter which will read at most `limit` bytes from it. Read more
Source§

#### fn read_array<const N: usize>(&mut self) -> Result<[u8; N]>
where Self: Sized,

🔬This is a nightly-only experimental API. (`read_array` #148848)
Read and return a fixed array of bytes from this source. Read more

## Auto Trait Implementations§

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### impl Freeze for Stdin

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### impl RefUnwindSafe for Stdin

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### impl Send for Stdin

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### impl Sync for Stdin

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### impl Unpin for Stdin

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### impl UnwindSafe for Stdin

## 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.