waitpid - wait for a particular child process to die

- NAME
- SYNOPSIS
- DESCRIPTION

# NAME

waitpid - wait for a particular child process to die

# SYNOPSIS

waitpid PID,FLAGS

# DESCRIPTION

Waits for a particular child process to terminate and returns the pid of the deceased process, or `-1` if there is no such child process. On some systems, a value of 0 indicates that there are processes still running. The status is returned in `$?`. If you say

        use POSIX ":sys_wait_h";
        #...
        do {
            $kid = waitpid(-1, WNOHANG);
        } until $kid > 0;

then you can do a non-blocking wait for all pending zombie processes. Non-blocking wait is available on machines supporting either the `waitpid(2)` or `wait4(2)` system calls. However, waiting for a particular pid with FLAGS of `0` is implemented everywhere. (Perl emulates the system call by remembering the status values of processes that have exited but have not been harvested by the Perl script yet.)

Note that on some systems, a return value of `-1` could mean that child processes are being automatically reaped. See the perlipc manpage for details, and for other examples.

waitpid - wait for a particular child process to die