library/std/src/sys/process/mod.rs

cfg_select! {
    target_family = "unix" => {
        mod unix;
        use unix as imp;
    }
    target_os = "windows" => {
        mod windows;
        use windows as imp;
    }
    target_os = "uefi" => {
        mod uefi;
        use uefi as imp;
    }
    target_os = "motor" => {
        mod motor;
        use motor as imp;
    }
    _ => {
        mod unsupported;
        use unsupported as imp;
    }
}

// This module is shared by all platforms, but nearly all platforms except for
// the "normal" UNIX ones leave some of this code unused.
#[cfg_attr(not(target_os = "linux"), allow(dead_code))]
mod env;

pub use env::CommandEnvs;
#[unstable(feature = "command_resolved_envs", issue = "149070")]
pub use env::CommandResolvedEnvs;
#[cfg(target_family = "unix")]
pub use imp::getppid;
pub use imp::{
    ChildPipe, Command, CommandArgs, EnvKey, ExitCode, ExitStatus, ExitStatusError, Process, Stdio,
    getpid, read_output,
};

#[cfg(any(
    all(
        target_family = "unix",
        not(any(
            target_os = "espidf",
            target_os = "horizon",
            target_os = "vita",
            target_os = "nuttx"
        ))
    ),
    target_os = "windows",
    target_os = "motor"
))]
pub fn output(cmd: &mut Command) -> crate::io::Result<(ExitStatus, Vec<u8>, Vec<u8>)> {
    let (mut process, mut pipes) = cmd.spawn(Stdio::MakePipe, false)?;

    drop(pipes.stdin.take());
    let (mut stdout, mut stderr) = (Vec::new(), Vec::new());
    match (pipes.stdout.take(), pipes.stderr.take()) {
        (None, None) => {}
        (Some(out), None) => {
            let res = out.read_to_end(&mut stdout);
            res.unwrap();
        }
        (None, Some(err)) => {
            let res = err.read_to_end(&mut stderr);
            res.unwrap();
        }
        (Some(out), Some(err)) => {
            let res = read_output(out, &mut stdout, err, &mut stderr);
            res.unwrap();
        }
    }

    let status = process.wait()?;
    Ok((status, stdout, stderr))
}

#[cfg(not(any(
    all(
        target_family = "unix",
        not(any(
            target_os = "espidf",
            target_os = "horizon",
            target_os = "vita",
            target_os = "nuttx"
        ))
    ),
    target_os = "windows",
    target_os = "motor"
)))]
pub use imp::output;