sigwait(2)                     DG/UX R4.11MU05                    sigwait(2)


NAME
       sigwait - wait for an asynchronous signal

SYNOPSIS
       #include <signal.h>
       int     sigwait(sigsett *set)
       int     sigsett *set


   where:
       set       A pointer to a set of signals for which the caller will
                 wait.

DESCRIPTION
       Sigwait chooses a pending signal from set, atomically clears it from
       the set of pending signals for the process, and returns that signal
       number.  If no signal in set is pending at the time of the call, the
       thread is suspended until one or more signals in set becomes pending.
       Only a signal whose action is SIG_DFL or a signal handler will be
       pended and cause the calling thread to wake up.  The normal delivery
       actions of the signal (either the default action or going to a
       signal-catching function) will not occur, instead sigwait will return
       with the signal number of the signal.

       Set cannot include either SIGKILL or SIGSTOP.  Set can include
       signals whose action is SIG_IGN.  However, since an ignored signal is
       not pended, the thread will not be awakened for such a signal.

       If more than one thread is using sigwait(2) to wait for the same
       signal, one of those threads returns from sigwait(2) with the signal
       number.  Which thread returns from sigwait(2) if more than one signal
       thread is waiting is unspecified.

RETURN VALUE
       Upon successful completion, sigwait(2) returns the signal number of
       the received signal.  Otherwise, -1 is returned and errno is set to
       indicate the error.

DIAGNOSTICS
       If any of the following conditions occurs, sigwait(2) returns -1 and
       sets errno to the corresponding value:

       EINVAL    The set argument contains either SIGKILL or SIGSTOP, or an
                 unsupported signal number.

NOTES
       This implementation of sigwait is based on draft 6 of the POSIX
       threads standard, then called 1003.4A, now called 1003.1C.  In order
       to ensure compatibility with the final version of the standard,
       define the macro POSIX4ADRAFT6SOURCE (with #define or -D) where
       <signal.h> is included and sigwait is used.

SEE ALSO
       sigaction(2), sigprocmask(2), sigsuspend(2), pause(2), signal(2).

COPYRIGHTS
       Portions of this text are reprinted from IEEE Std 1003.4a Draft 6,
       Thread Extension for Portable Operating Systems© by the Institute of
       Electrical and Electronics Engineers, Inc., with the permission of
       the IEEE Standards Department.  To purchase IEEE Standards, call
       800-678-IEEE.

       In the event of a discrepancy between the electronic and the printed
       version, the printed version takes precedence.


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