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

       sigwaitinfo() removes the delivered signal from the  calling  process’s
       list  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 process 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.  (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 handlers 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()).

       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), signal(7), time(7)

COLOPHON

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