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waitpid PID,FLAGS

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waitpid PID,FLAGS

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. The status is returned in $?. If you say

    use POSIX ":sys_wait_h";
    ...
    waitpid(-1,&WNOHANG);

then you can do a non-blocking wait for any process. 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.)

Source: Perl builtin functions
Copyright: Larry Wall, et al.

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