sigqueue(2)							System Calls Manual						       sigqueue(2)

NAME

       sigqueue() - queue a signal to a process

SYNOPSIS

DESCRIPTION

       The  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
       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 system call.

       The  system  call  returns  immediately.   If is set for signo at the receiving process (see sigqueue(2)) and if resources are available to
       queue the signal, the signal will be queued and sent to the receiving process.  When  the  signal  is  delivered  or  accepted,	the  field
       si_value  of  the  siginfo parameter (see signal(5)) will be set to value.  If is not set for signo, then signo, but not necessarily value,
       will 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, either signo or at least one pending
       unblocked  signal  will	be delivered to the sending process before the system call returns.  Should any of multiple pending signals in the
       range to be selected for delivery or acceptance, it will be the lowest numbered one.  The selection order between realtime and non-realtime
       signals, or between multiple pending non-realtime signals, is unspecified.

   Application Usage
       Threads Considerations

       can be used to post signals to another process but can not be used to post signals to a specific thread in another 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 function for signo, either signo or at least  one  pending  unblocked  signal  will	be
       delivered to the calling thread before the function returns.

       LWP Considerations

       Signals can not be posted to specific Lightweight Processes (LWPs) in another process.

   Security Restrictions
       Some  or all of the actions associated with this system call are subject to compartmental restrictions. See compartments(5) for more infor-
       mation about compartmentalization on systems that support that feature.	Compartmental restrictions can be overridden if the  process  pos-
       sesses  the  privilege  (COMMALLOWED).  Processes owned by the superuser may not have this privilege.  Processes owned by any user may have
       this privilege, depending on system configuration.

       Some or all of the actions associated with this system call require one or more privileges.  Processes owned by the  superuser  have  many,
       though  not  all,  privileges.  Processes owned by other users may have privilege(s), depending on system configuration.  See privileges(5)
       for more information about privileged access on systems that support fine-grained privileges.

RETURN VALUE

       Upon successful completion, the specified signal will be queued, and the function returns a value of (zero).   Otherwise,  a  value  of	is
       returned, and is set to indicate the error.

ERRORS

       fails and no signal is sent if any of the following conditions occur:

	      No resources are available to queue the signal.
			     The  process has already queued signals that are still pending at the receiver(s), or a systemwide resource limit has
			     been exceeded.

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

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

	      The process    pid does not exist.

SEE ALSO

       kill(2), sysconf(2), privileges(5), signal(5).

																       sigqueue(2)