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SIGQUEUE(3) Linux Programmer's Manual SIGQUEUE(3)
sigqueue - 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, this function is implemented using the rt_sigqueueinfo(2) system
call. The system call 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, uinfo, is initialized
as follows:
uinfo.si_signo = sig; /* argument supplied to sigqueue() */
uinfo.si_code = SI_QUEUE;
uinfo.si_pid = getpid(); /* Process ID of sender */
uinfo.si_uid = getuid(); /* Real UID of sender */
uinfo.si_value = val; /* argument supplied to sigqueue() */
kill(2), rt_sigqueueinfo(2), sigaction(2), signal(2), pthread_sigqueue(3),
sigwait(3), signal(7)
This page is part of release 3.41 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 2012-03-25 SIGQUEUE(3)
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