Suspends a calling thread and waits for queued signals to arrive.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <signal.h>

      int sigwait  (const sigset_t set, int *sig);

1  –  Arguments

 set

    The set of signals to wait for.

 sig

    Returns the signal number of the selected signal.

2  –  Description

    The sigwait function suspends the calling thread until at least
    one of the signals in the set argument is in the caller's set
    of pending signals. When this happens, one of those signals
    is automatically selected and removed from the set of pending
    signals. The signal number identifying that signal is then
    returned in the location referenced by sig.

    The effect is unspecified if any signals in the set argument are
    not blocked when the sigwait function is called.

    The set argument is created using the set manipulation functions
    sigemptyset, sigfillset, sigaddset, and sigdelset.

    If, while the sigwait function is waiting, a signal occurs that
    is eligible for delivery (that is, not blocked by the signal
    mask), that signal is handled asynchronously and the wait is
    interrupted.

    See also sigtimedwait and sigwaitinfo.

    See the "Error and Signal Handling" chapter of the VSI C RTL
    Reference Manual for more information on signal handling.

3  –  Return Values

    0                  Upon successful completion, sigwait stores the
                       signal number of the received signal at the
                       location referenced by sig and returns 0.
    nonzero            Indicates that an error occurred; errno is set
                       to the following value:

                       o  EINVAL - The set argument contains an
                          invalid or unsupported signal number.