SIGQUEUE(3)							   SIGQUEUE(3)

NAME    [Toc]    [Back]

     sigqueue -	queue a	signal to a process  (POSIX)

C SYNOPSIS    [Toc]    [Back]

     #include <signal.h>

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

DESCRIPTION    [Toc]    [Back]

     The function sigqueue() 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
     validity of pid.

     The conditions required for a process to have permission to queue a
     signal to another process are the same as for the kill(2) function.

     If	the signal specified in	signo is currently blocked for the receiving
     process, sigqueue() shall return immediately and, if SA_SIGINFO is	set
     for signo and if the resources were available to queue the	signal,	the
     signal shall be left queued and pending. Furthermore, when	the signal
     handler for signo is delivered, the field si_code of the passed in
     siginfo structure will be set to SI_QUEUE (see sigaction(2), signal(5)).
     If	SA_SIGINFO is not set for signo, then signo, but not necessarily
     value, shall be sent at least once	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 function for signo,	at
     least one pending unblocked signal	shall be delivered to the calling
     thread before the sigqueue() function returns.

SEE ALSO    [Toc]    [Back]

     kill(2), sigaction(2), sigwait(3),	signal(5).

DIAGNOSTICS    [Toc]    [Back]

     Upon successful completion, the sigqueue()	function returns a value of 0
     indicating	that the specified signal has been queued. Otherwise a value
     of	-1 is returned and errno is set	to indicate the	error.	If any of the
     conditions	below occur, the sigqueue() function shall return -1 and set
     errno to the corresponding	value:

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

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





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SIGQUEUE(3)							   SIGQUEUE(3)



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

     [ESRCH]	    The	process	pid does not exist.

WARNING    [Toc]    [Back]

     The POSIX and System V signal facilities have different semantics.	 Using
     both facilities in	the same program is strongly discouraged and will
     result in unpredictable behavior.


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