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Redirect output of child process spawned from Rust

I need to redirect output of a spawned child process. This is what I tried but it doesn't work:

Command::new(cmd)
    .args(&["--testnet",
            "--fast",
            format!("&>> {}", log_path).as_str()])
    .stdin(Stdio::piped())
    .stdout(Stdio::inherit())
    .spawn()
Solution

  • To directly use a file as output without intermediate copying from a pipe, you have to pass the file descriptor. The code is platform-specific, but with conditional compilation you can make it work on Windows too.

    let f = File::create("foo.log").unwrap();
let fd = f.as_raw_fd();
// from_raw_fd is only considered unsafe if the file is used for mmap
let out = unsafe {Stdio::from_raw_fd(fd)};
let child = Command::new("foo")
    .stdout(out)
    .spawn().unwrap();