rust - 如何确保在每次迭代后释放每个 `Child` 进程的文件句柄？

Question

我采取了以下程序 from the Rust docs for std::process::Command .它在一些迭代后停止工作。

use std::process::Command;
use std::process::Stdio;

fn main() {
    loop {
        let mut echo_child = Command::new("echo")
            .arg("oh no a tpyo")
            .stdout(Stdio::piped())
            .spawn()
            .expect("failed to start 'echo'");

        let echo_out = echo_child.stdout.expect("failed to open 'echo' stdout");

        let sed_child = Command::new("sed")
            .arg("s/tpyo/typo/")
            .stdin(Stdio::from(echo_out))
            .stdout(Stdio::piped())
            .spawn()
            .expect("failed to start 'sed'");

        let sed_out = sed_child
            .wait_with_output()
            .expect("failed to wait on 'sed'");
        let sed_out_slice = sed_out.stdout.as_slice();
        assert_eq!(b"oh no a typo\n", sed_out_slice);
        println!("out: {:?}", String::from_utf8_lossy(sed_out_slice));
    }
}

每次它崩溃时，我都会收到以下输出:

thread 'main' panicked at 'failed to start 'sed': Error { repr: Os { code: 35, message: "Resource temporarily unavailable" } }', src/libcore/result.rs:906:4

根据 the docs for Child (我从哪里得到这个程序)，它说:

There is no implementation of Drop for child processes, so if you do not ensure the Child has exited then it will continue to run, even after the Child handle to the child process has gone out of scope.

如何确保在每次迭代后释放每个 Child 进程的文件句柄？

Answer 1

如果您在引用的段落之后立即阅读段落:

Calling wait (or other functions that wrap around it) will make the parent process wait until the child has actually exited before continuing.

为了调用wait，您不需要将stdout移出Child:

let echo_out = echo_child.stdout.take().expect("failed to open 'echo' stdout");

// ...

echo_child.wait().expect("Couldn't wait for echo child");

另见:

• Kill child process while waiting for it