NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
SIGQUEUE(2) Linux Programmer's Manual SIGQUEUE(2)
sigqueue, rt_sigqueueinfo - queue a signal and data to a process
#include <signal.h>
int sigqueue(pid_t pid, int sig, const union sigval value);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sigqueue(): _POSIX_C_SOURCE >= 199309L
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.
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.
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.
This system call first appeared in Linux 2.2.
POSIX.1-2001.
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() */
kill(2), sigaction(2), signal(2), sigwait(3), signal(7)
This page is part of release 3.23 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/.
Linux 2007-07-26 SIGQUEUE(2)