Function stderr 

pub fn stderr() -> Stderr 

Constructs a new handle to the standard error of the current process.

This handle is not buffered.

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.

Examples

Using implicit synchronization:

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

fn main() -> io::Result<()> {
    io::stderr().write_all(b"hello world")?;

    Ok(())
}

Using explicit synchronization:

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

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

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

    Ok(())
}