NAME

       sigtimedwait, sigwaitinfo — wait for queued signals (REALTIME)

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <signal.h>

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

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

DESCRIPTION

       The sigtimedwait() system call is equivalent  to  sigwaitinfo()  except  that  if  none  of  the  signals
       specified  by  set  are  pending,  sigtimedwait()  waits  for the time interval specified in the timespec
       structure referenced by timeout.  If the timespec structure pointed to by timeout is zero-valued  and  if
       none  of the signals specified by set are pending, then sigtimedwait() returns immediately with an error.
       If timeout is the NULL pointer, the behavior is unspecified.  CLOCK_MONOTONIC clock is  used  to  measure
       the time interval specified by the timeout argument.

       The  sigwaitinfo()  system  call selects the pending signal from the set specified by set.  Should any of
       multiple pending signals in the range SIGRTMIN to SIGRTMAX be selected, it shall be the  lowest  numbered
       one.   The  selection  order  between realtime and non-realtime signals, or between multiple pending non-
       realtime signals, is unspecified.  If no signal in set is pending at the time of the  call,  the  calling
       thread  is  suspended  until  one  or more signals in set become pending or until it is interrupted by an
       unblocked, caught signal.

       The sigwaitinfo() system call is equivalent to the sigwait() system call if the info  argument  is  NULL.
       If  the info argument is non-NULL, the sigwaitinfo() function is equivalent to sigwait(), except that the
       selected signal number shall be stored in the si_signo member, and the  cause  of  the  signal  shall  be
       stored in the si_code member.  Besides this, the sigwaitinfo() and sigtimedwait() system calls may return
       EINTR if interrupted by signal, which is not allowed for the sigwait() function.

       If  any  value is queued to the selected signal, the first such queued value is dequeued and, if the info
       argument is non-NULL, the value is stored in the si_value member of info.  The system  resource  used  to
       queue  the  signal  is  released  and  returned  to the system for other use.  If no value is queued, the
       content of the si_value member is zero-valued.  If no further signals are queued for the selected signal,
       the pending indication for that signal is reset.

RETURN VALUES

       Upon successful completion (that is, one of the signals specified by set  is  pending  or  is  generated)
       sigwaitinfo()  and  sigtimedwait()  return the selected signal number.  Otherwise, the functions return a
       value of -1 and set the global variable errno to indicate the error.

ERRORS

       The sigtimedwait() system call will fail if:

       [EAGAIN]           No signal specified by set was generated within the specified timeout period.

       The sigtimedwait() and sigwaitinfo() system calls fail if:

       [EINTR]            The wait was interrupted by an unblocked, caught signal.

       The sigtimedwait() system call may also fail if:

       [EINVAL]           The timeout argument specified a tv_nsec value less than zero or greater than or equal
                          to 1000 million.  Kernel only checks for this error if no signal is pending in set and
                          it is necessary to wait.

SEE ALSO

       sigaction(2),  sigpending(2),  sigqueue(2),  sigsuspend(2),  sigwait(2),  pause(3),   pthread_sigmask(3),
       siginfo(3)

STANDARDS

       The sigtimedwait() and sigwaitinfo() system calls conform to ISO/IEC 9945-1:1996 (“POSIX.1”).

Debian                                         September 27, 2012                                SIGTIMEDWAIT(2)