The wait function suspends the parent process until the final
    status of a terminated child is returned from the child.

    On OpenVMS Version 7.0 and higher systems, the wait function is
    equivalent to waitpid( 0, status, 0 ) if you include <wait.h> and
    compile with the _POSIX_EXIT feature-test macro set (either with
    /DEFINE=_POSIX_EXIT or with #define _POSIX_EXIT at the top of
    your file, before any file inclusions).