Struct Stderr 

pub struct Stderr { /* private fields */ }

Available on crate features std only.

🔌 std A handle to the standard error stream of a process.

---

^{📍sys/io re-exported from std::io}

---

---

📜
A handle to the standard error stream of a process.

For more information, see the io::stderr 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 write 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.

Implementations

impl Stderr

pub fn lock(&self) -> StderrLock<'static>

Locks this handle to the standard error stream, returning a writable guard.

The lock is released when the returned lock goes out of scope. The returned guard also implements the Write trait for writing data.

Examples

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

fn foo() -> io::Result<()> {
    let stderr = io::stderr();
    let mut handle = stderr.lock();

    handle.write_all(b"hello world")?;

    Ok(())
}

Trait Implementations

impl AsFd for Stderr

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor.

impl AsRawFd for Stderr

fn as_raw_fd(&self) -> i32

Extracts the raw file descriptor.

impl Debug for Stderr

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

Formats the value using the given formatter.

impl From<Stderr> for Stdio

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());

impl IsTerminal for Stderr

fn is_terminal(&self) -> bool

Returns true if the descriptor/handle refers to a terminal/tty.

impl RefUnwindSafe for Stderr

impl StdioExt for Stderr

fn set_fd<T>(&mut self, fd: T) -> Result<(), Error>

where T: Into<OwnedFd>,

🔬This is a nightly-only experimental API. (stdio_swap)

Redirects the stdio file descriptor to point to the file description underpinning fd.

fn take_fd(&mut self) -> Result<OwnedFd, Error>

🔬This is a nightly-only experimental API. (stdio_swap)

Redirects the stdio file descriptor to the null device (/dev/null) and returns a new OwnedFd backed by the previous file description.

fn replace_fd<T>(&mut self, replace_with: T) -> Result<OwnedFd, Error>

where T: Into<OwnedFd>,

🔬This is a nightly-only experimental API. (stdio_swap)

Redirects the stdio file descriptor and returns a new OwnedFd backed by the previous file description.

impl TextOut for Stderr

Emits UTF-8 text to the process standard error stream.

type Error = Error

The error returned when text emission fails.

fn write_text(&mut self, text: &str) -> Result<(), Self::Error>

Emits text without appending a line ending.

fn write_line(&mut self, text: &str) -> Result<(), Self::Error>

Emits text followed by \n.

fn write_char(&mut self, c: char) -> Result<(), Self::Error>

Emits a single Unicode scalar.

fn write_fmt(&mut self, args: FmtArguments<'_>) -> Result<(), Self::Error>

Emits formatted text.

impl UnwindSafe for Stderr

impl Write for Stderr

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

Writes a buffer into this writer, returning how many bytes were written.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn flush(&mut self) -> Result<(), Error>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, args: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.

impl Write for &Stderr

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

Writes a buffer into this writer, returning how many bytes were written.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn flush(&mut self) -> Result<(), Error>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, args: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.