Function wait_any 

pub fn wait_any() -> Result<(pid_t, c_int)>

Wait for any child process to terminate see wait(2)

This is equivalent to waitpid(-1, ...): it blocks until any child process terminates, then returns both the PID that was reaped and its raw status.

Use this when supervising multiple children. Unlike waitpid(), which is aimed at a specific child PID and returns only the status, this function preserves the child PID returned by the underlying waitpid system call.

Reaping behavior

Because this calls waitpid(-1, ...), it reaps any child of the current process — including children spawned by other parts of the program, such as std::process::Command. If you reap such a child here, the standard library’s std::process::Child::wait/try_wait will later fail with ECHILD because the child no longer exists. Only use wait_any() in programs that manage all of their children directly through this crate.

Behavior

• Blocks until any child terminates
• Retries automatically on EINTR (interrupted by signal)
• Returns (pid, status) where pid identifies the child that was reaped
• Returns the raw status (use libc::WIFEXITED, libc::WEXITSTATUS, etc.)

Errors

Returns an io::Error if the waitpid system call fails. Common errors include:

• No unwaited-for child processes exist (ECHILD)
• Invalid options

Example

use fork::{fork, wait_any, Fork, WEXITSTATUS, WIFEXITED};

match fork::fork() {
    Ok(Fork::Parent(child)) => {
        let (pid, status) = wait_any()?;
        assert_eq!(pid, child);
        assert!(WIFEXITED(status));
        assert_eq!(WEXITSTATUS(status), 0);
    }
    Ok(Fork::Child) => std::process::exit(0),
    Err(e) => eprintln!("Fork failed: {e}"),
}