should we make clear std::process::ChildStdout is non-blocking or not?

[hicqu]

I'm working with std::process::Child::try_wait and std::process::ChildStdout. Here is an example,

let mut child = cmd.spawn().unwrap();
loop {
    let mut buf = [0 as u8; 4096];
    if let Some(ref stream) = child.stdout {
        stream.read(&mut buf).unwrap();           // Will it block?
    }
    match child.try_wait() {
        // something here ...
    }
}

I could not find stream.read(&mut buf) would block or not in API document. I test that simple code on Linux and it didn't blocking. So,

1. On other platforms, will it block or not?
2. Should we make clear that for every platform?
3. Or it's just an undefined behavor, we should set that stream blocking or nonblocking explicitly?

Please help me. Thanks very much!

[alexcrichton]

Yes on all platforms all I/O in libstd is blocking by default, if not it's a bug!

[hicqu]

This means that we should make it clear that std::process:ChildStdout.read is nonblocking in documents, right?

Thank you for continually improving this amazing language!

[alexcrichton]

Did you mean blocking as opposed to nonblocking? If so, indeed!

[hicqu]

Ok, you are right, it's blocking but not nonblocking. Thank you!