SIGWAITINFO(2)						     Linux Programmer's Manual						    SIGWAITINFO(2)

NAME

       sigwaitinfo, sigtimedwait - synchronously wait for queued signals

SYNOPSIS

       #include <signal.h>

       int sigwaitinfo(const sigset_t *set, siginfo_t *info);

       int sigtimedwait(const sigset_t *set, siginfo_t *info,
			const struct timespec *timeout);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       sigwaitinfo(), sigtimedwait(): _POSIX_C_SOURCE >= 199309L

DESCRIPTION

       sigwaitinfo()  suspends	execution  of  the  calling thread until one of the signals in set is delivered.  (If one of the signals in set is
       already pending for the calling thread, sigwaitinfo() will return immediately with information about that signal.)

       sigwaitinfo() removes the delivered signal from the set of pending signals and returns the signal number as its function  result.   If  the
       info argument is not NULL, then it returns a structure of type siginfo_t (see sigaction(2)) containing information about the signal.

       Signals returned via sigwaitinfo() are delivered in the usual order; see signal(7) for further details.

       sigtimedwait() operates in exactly the same way as sigwaitinfo() except that it has an additional argument, timeout, which enables an upper
       bound to be placed on the time for which the thread is suspended.  This argument is of the following type:

	   struct timespec {
	       long    tv_sec;	       /* seconds */
	       long    tv_nsec;        /* nanoseconds */
	   }

       If both fields of this structure are specified as 0, a poll is performed: sigtimedwait() returns immediately, either with information about
       a signal that was pending for the caller, or with an error if none of the signals in set was pending.

RETURN VALUE

       On  success,  both sigwaitinfo() and sigtimedwait() return a signal number (i.e., a value greater than zero).  On failure both calls return
       -1, with errno set to indicate the error.

ERRORS

       EAGAIN No signal in set was delivered within the timeout period specified to sigtimedwait().

       EINTR  The wait was interrupted by a signal handler; see signal(7).  (This handler was for a signal other than one of those in set.)

       EINVAL timeout was invalid.

CONFORMING TO

       POSIX.1-2001.

NOTES

       In normal usage, the calling program blocks the signals in set via a prior call to sigprocmask(2) (so  that  the  default  disposition  for
       these signals does not occur if they are delivered between successive calls to sigwaitinfo() or sigtimedwait()) and does not establish han-
       dlers for these signals.  In a multithreaded program, the signal should be blocked in all threads to prevent the signal being delivered	to
       a thread other than the one calling sigwaitinfo() or sigtimedwait()).

       The  set  of signals that is pending for a given thread is the union of the set of signals that is pending specifically for that thread and
       the set of signals that is pending for the process as a whole (see signal(7)).

       If multiple threads of a process are blocked waiting for the same signal(s) in sigwaitinfo() or sigtimedwait(), then  exactly  one  of  the
       threads will actually receive the signal if it is delivered to the process as a whole; which of the threads receives the signal is indeter-
       minate.

       POSIX leaves the meaning of a NULL value for the timeout argument of sigtimedwait() unspecified, permitting the possibility that  this  has
       the same meaning as a call to sigwaitinfo(), and indeed this is what is done on Linux.

       On Linux, sigwaitinfo() is a library function implemented on top of sigtimedwait().

SEE ALSO

       kill(2), sigaction(2), signal(2), signalfd(2), sigpending(2), sigprocmask(2), sigqueue(2), sigsetops(3), sigwait(3), signal(7), time(7)

COLOPHON

       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-10-04							    SIGWAITINFO(2)