SIGSUSPEND(2)                        SysV                        SIGSUSPEND(2)



NAME
     sigsuspend - wait for a signal and atomically change a set of blocked
     signals

SYNOPSIS
     #include <signal.h>

     int sigsuspend (signal_mask)
     const sigset_t *signal_mask;

DESCRIPTION
     The sigsuspend function replaces the signal mask of the process with the
     set of signals pointed to by the signal_mask argument, and then suspends
     execution of the process until delivery of a signal whose action is
     either to execute a signal handler or to terminate the process.

     If delivery of a signal causes the process to terminate, the sigsuspend
     function does not return. If delivery of a signal causes a signal-
     catching function to execute, the sigsuspend function returns after the
     signal-catching function returns, with the signal mask restored to the
     set that existed prior to the call to the sigsuspend function.

     It is not possible to block signals which cannot be ignored. That is
     enforced by the system without causing an error to be indicated.

     Applications should call either sigemptyset(3) or sigfillset(3) at least
     once for each object of type sigset_t prior to any other use of that
     object.  If such an object is not initialized in this way, but is
     nonetheless supplied as an argument to the sigsuspend function, the
     results are undefined.

NOTES
     Domain/OS also supplies the sigpause(2) function; sigpause(2) provides a
     subset of the sigsuspend functionality.

     The sigsuspend function sets the signal mask and waits for an unblocked
     signal as one atomic operation. This means that signals cannot occur
     between the operations of setting the mask and waiting for a signal.  If
     a program invokes sigprocmask(SIG_SETMASK) and sigpause(2) separately, a
     signal that occurs between these functions might not be noticed by
     sigpause(2).

DIAGNOSTICS
     Since sigsuspend suspends process execution indefinitely, there is no
     successful completion return value. If a return occurs, a value of -1 is
     returned and errno is set to indicate the error.

ERRORS
     sigsuspend fails if:

     [EINTR]   A signal is caught by the calling process and control is
               returned from the signal handler.

SEE ALSO
     pause(2), sigaction(2), sigpending(2), sigprocmask(2), sigpause(2),
     sigsetops(3)