broker_tokio/io/
stderr.rs

1use crate::io::blocking::Blocking;
2use crate::io::AsyncWrite;
3
4use std::io;
5use std::pin::Pin;
6use std::task::Context;
7use std::task::Poll;
8
9cfg_io_std! {
10    /// A handle to the standard error stream of a process.
11    ///
12    /// Concurrent writes to stderr must be executed with care: Only individual
13    /// writes to this [`AsyncWrite`] are guaranteed to be intact. In particular
14    /// you should be aware that writes using [`write_all`] are not guaranteed
15    /// to occur as a single write, so multiple threads writing data with
16    /// [`write_all`] may result in interleaved output.
17    ///
18    /// Created by the [`stderr`] function.
19    ///
20    /// [`stderr`]: stderr()
21    /// [`AsyncWrite`]: AsyncWrite
22    /// [`write_all`]: crate::io::AsyncWriteExt::write_all()
23    ///
24    /// # Examples
25    ///
26    /// ```
27    /// use tokio::io::{self, AsyncWriteExt};
28    ///
29    /// #[tokio::main]
30    /// async fn main() -> io::Result<()> {
31    ///     let mut stderr = io::stdout();
32    ///     stderr.write_all(b"Print some error here.").await?;
33    ///     Ok(())
34    /// }
35    /// ```
36    #[derive(Debug)]
37    pub struct Stderr {
38        std: Blocking<std::io::Stderr>,
39    }
40
41    /// Constructs a new handle to the standard error of the current process.
42    ///
43    /// The returned handle allows writing to standard error from the within the
44    /// Tokio runtime.
45    ///
46    /// Concurrent writes to stderr must be executed with care: Only individual
47    /// writes to this [`AsyncWrite`] are guaranteed to be intact. In particular
48    /// you should be aware that writes using [`write_all`] are not guaranteed
49    /// to occur as a single write, so multiple threads writing data with
50    /// [`write_all`] may result in interleaved output.
51    ///
52    /// [`AsyncWrite`]: AsyncWrite
53    /// [`write_all`]: crate::io::AsyncWriteExt::write_all()
54    ///
55    /// # Examples
56    ///
57    /// ```
58    /// use tokio::io::{self, AsyncWriteExt};
59    ///
60    /// #[tokio::main]
61    /// async fn main() -> io::Result<()> {
62    ///     let mut stderr = io::stdout();
63    ///     stderr.write_all(b"Print some error here.").await?;
64    ///     Ok(())
65    /// }
66    /// ```
67    pub fn stderr() -> Stderr {
68        let std = io::stderr();
69        Stderr {
70            std: Blocking::new(std),
71        }
72    }
73}
74
75impl AsyncWrite for Stderr {
76    fn poll_write(
77        mut self: Pin<&mut Self>,
78        cx: &mut Context<'_>,
79        buf: &[u8],
80    ) -> Poll<io::Result<usize>> {
81        Pin::new(&mut self.std).poll_write(cx, buf)
82    }
83
84    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
85        Pin::new(&mut self.std).poll_flush(cx)
86    }
87
88    fn poll_shutdown(
89        mut self: Pin<&mut Self>,
90        cx: &mut Context<'_>,
91    ) -> Poll<Result<(), io::Error>> {
92        Pin::new(&mut self.std).poll_shutdown(cx)
93    }
94}
broker_tokio/io/stderr.rs

broker_tokio/io/
stderr.rs
