Name
sigqueue, rt_sigqueueinfo — queue a signal and data to a process
Synopsis
#include <signal.h>
int
sigqueue( |
pid_t | pid, |
| int | sig, | |
| const union sigval | value); |
![[Note]](../stylesheet/note.png) |
Note | ||
|---|---|---|---|
|
DESCRIPTION
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
-
sigwas 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.
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(); info.si_uid = getuid(); info.si_value = val; // argument supplied to sigqueue()
COLOPHON
This page is part of release 2.79 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/.
|
Copyright (c) 2002 Michael Kerrisk <mtk.manpagesgmail.com> Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. added note on self-signaling, aeb, 2002-06-07 added note on CAP_KILL, mtk, 2004-06-16 |