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SIGQUEUE(2)		  FreeBSD System Calls Manual		   SIGQUEUE(2)

NAME
     sigqueue -- queue a signal	to a process (REALTIME)

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <signal.h>

     int
     sigqueue(pid_t pid, int signo, const union	sigval value);

DESCRIPTION
     The sigqueue() system call	causes the signal specified by signo to	be
     sent with the value specified by value to the process specified by	pid.
     If	signo is zero (the null	signal), error checking	is performed but no
     signal is actually	sent.  The null	signal can be used to check the	valid-
     ity of PID.

     The conditions required for a process to have permission to queue a sig-
     nal to another process are	the same as for	the kill(2) system call.  The
     sigqueue()	system call queues a signal to a single	process	specified by
     the pid argument.

     The sigqueue() system call	returns	immediately.  If the resources were
     available to queue	the signal, the	signal will be queued and sent to the
     receiving process.

     If	the value of pid causes	signo to be generated for the sending process,
     and if signo is not blocked for the calling thread	and if no other	thread
     has signo unblocked or is waiting in a sigwait() system call for signo,
     either signo or at	least the pending, unblocked signal will be delivered
     to	the calling thread before sigqueue() returns.  Should any multiple
     pending signals in	the range SIGRTMIN to SIGRTMAX be selected for deliv-
     ery, it is	the lowest numbered one.  The selection	order between realtime
     and non-realtime signals, or between multiple pending non-realtime	sig-
     nals, is unspecified.

RETURN VALUES
     Upon successful completion, the value 0 is	returned; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The sigqueue() system call	will fail if:

     [EAGAIN]		No resources are available to queue the	signal.	 The
			process	has already queued {SIGQUEUE_MAX} signals that
			are still pending at the receiver(s), or a system-wide
			resource limit has been	exceeded.

     [EINVAL]		The value of the signo argument	is an invalid or
			unsupported signal number.

     [EPERM]		The process does not have the appropriate privilege to
			send the signal	to the receiving process.

     [ESRCH]		The process pid	does not exist.

SEE ALSO
     kill(2), sigaction(2), sigpending(2), sigqueue(2),	sigsuspend(2),
     sigtimedwait(2), sigwait(2), sigwaitinfo(2), pause(3),
     pthread_sigmask(3), siginfo(3)

STANDARDS
     The sigqueue() system call	conforms to IEEE Std 1003.1-2004
     (``POSIX.1'').

HISTORY
     Support for POSIX realtime	signal queue first appeared in FreeBSD 7.0.

FreeBSD	9.2			March 10, 2012			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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