mirror of https://github.com/mkerrisk/man-pages
152 lines
4.2 KiB
Groff
152 lines
4.2 KiB
Groff
.\" Copyright (c) 2002 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" added note on self-signaling, aeb, 2002-06-07
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.\" added note on CAP_KILL, mtk, 2004-06-16
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.\"
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.TH SIGQUEUE 2 2007-07-26 "Linux" "Linux Programmer's Manual"
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.SH NAME
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sigqueue, rt_sigqueueinfo \- queue a signal and data to a process
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.SH SYNOPSIS
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.B #include <signal.h>
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.sp
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.BI "int sigqueue(pid_t " pid ", int " sig ", const union sigval " value );
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR sigqueue ():
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_POSIX_C_SOURCE\ >=\ 199309L
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.SH DESCRIPTION
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.BR sigqueue ()
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sends the signal specified in
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.I sig
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to the process whose PID is given in
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.IR pid .
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The permissions required to send a signal are the same as for
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.BR kill (2).
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As with
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.BR kill (2),
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the null signal (0) can be used to check if a process with a given
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PID exists.
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.PP
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The
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.I value
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argument is used to specify an accompanying item of data (either an integer
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or a pointer value) to be sent with the signal, and has the following type:
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.sp
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.in +4n
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.nf
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union sigval {
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int sival_int;
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void *sival_ptr;
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};
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.fi
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.in
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If the receiving process has installed a handler for this signal using the
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.B SA_SIGINFO
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flag to
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.BR sigaction (2),
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then it can obtain this data via the
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.I si_value
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field of the
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.I siginfo_t
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structure passed as the second argument to the handler.
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Furthermore, the
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.I si_code
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field of that structure will be set to
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.BR SI_QUEUE .
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.SH "RETURN VALUE"
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On success,
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.BR sigqueue ()
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returns 0, indicating that the signal was successfully
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queued to the receiving process.
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Otherwise \-1 is returned and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EAGAIN
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The limit of signals which may be queued has been reached.
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(See
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.BR signal (7)
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for further information.)
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.TP
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.B EINVAL
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.I sig
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was invalid.
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.TP
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.B EPERM
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The process does not have permission to send the signal
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to the receiving process.
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For the required permissions, see
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.BR kill (2).
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.TP
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.B ESRCH
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No process has a PID matching
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.IR pid .
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.SH VERSIONS
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This system call first appeared in Linux 2.2.
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.SH "CONFORMING TO"
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POSIX.1-2001.
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.SH NOTES
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If this function results in the sending of a signal to the process
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that invoked it, and that signal was not blocked by the calling thread,
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and no other threads were willing to handle this signal (either by
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having it unblocked, or by waiting for it using
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.BR sigwait (3)),
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then at least some signal must be delivered to this thread before this
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function returns.
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On Linux, the underlying system call is actually named
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.BR rt_sigqueueinfo (),
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and differs in its third argument, which is the
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.I siginfo_t
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structure that will be supplied to the receiving process's
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signal handler or returned by the receiving process's
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.BR sigtimedwait (2)
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call.
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Inside the glibc
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.BR sigqueue ()
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wrapper, this argument,
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.IR info ,
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is initialized as follows:
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.in +4n
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.nf
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info.si_signo = sig; /* argument supplied to sigqueue() */
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info.si_code = SI_QUEUE;
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info.si_pid = getpid(); /* Process ID of sender */
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info.si_uid = getuid(); /* Real UID of sender */
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info.si_value = val; /* argument supplied to sigqueue() */
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.fi
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.in
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.SH "SEE ALSO"
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.BR kill (2),
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.BR sigaction (2),
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.BR signal (2),
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.BR sigwait (3),
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.BR signal (7)
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