sigqueue()
sends the signal specified in
sig
to the process whose PID is given in
pid.
The permissions required to send a signal are the same as for
kill(2).
As with
kill(2),
the null signal (0) can be used to check if a process with a given
PID exists.
The
value
argument is used to specify an accompanying item of data (either an integer
or a pointer value) to be sent with the signal, and has the following type:
union sigval {
int sival_int;
void *sival_ptr;
};
If the receiving process has installed a handler for this signal using the
SA_SIGINFO
flag to
sigaction(2),
then it can obtain this data via the
si_value
field of the
siginfo_t
structure passed as the second argument to the handler.
Furthermore, the
si_code
field of that structure will be set to
SI_QUEUE.
RETURN VALUE
On success,
sigqueue()
returns 0, indicating that the signal was successfully
queued to the receiving process.
Otherwise -1 is returned and
errno
is set to indicate the error.
ERRORS
EAGAIN
The limit of signals which may be queued has been reached.
(See
signal(7)
for further information.)
EINVAL
sig
was invalid.
EPERM
The process does not have permission to send the signal
to the receiving process.
For the required permissions, see
kill(2).
ESRCH
No process has a PID matching
pid.
VERSIONS
This system call first appeared in Linux 2.2.
CONFORMING TO
POSIX.1-2001.
NOTES
If this function results in the sending of a signal to the process
that invoked it, and that signal was not blocked by the calling thread,
and no other threads were willing to handle this signal (either by
having it unblocked, or by waiting for it using
sigwait(3)),
then at least some signal must be delivered to this thread before this
function returns.
On Linux, the underlying system call is actually named
rt_sigqueueinfo(),
and differs in its third argument, which is the
siginfo_t
structure that will be supplied to the receiving process's
signal handler or returned by the receiving process's
sigtimedwait(2)
call.
Inside the glibc
sigqueue()
wrapper, this argument,
info,
is initialized as follows:
info.si_signo = sig; /* argument supplied to sigqueue() */
info.si_code = SI_QUEUE;
info.si_pid = getpid(); /* Process ID of sender */
info.si_uid = getuid(); /* Real UID of sender */
info.si_value = val; /* argument supplied to sigqueue() */
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
