1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
.\" Copyright (c) 2002 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" 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.\" manual page may be incorrect or out-of-date.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. The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.\" added note on self-signaling, aeb, 2002-06-07
.\" added note on CAP_KILL, mtk, 2004-06-16
.\"
.TH SIGQUEUE 3 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
sigqueue \- queue a signal and data to a process
.SH SYNOPSIS
.B #include <signal.h>
.PP
.BI "int sigqueue(pid_t " pid ", int " sig ", const union sigval " value );
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR sigqueue ():
_POSIX_C_SOURCE\ >=\ 199309L
.SH DESCRIPTION
.BR sigqueue ()
sends the signal specified in
.I sig
to the process whose PID is given in
.IR pid .
The permissions required to send a signal are the same as for
.BR kill (2).
As with
.BR kill (2),
the null signal (0) can be used to check if a process with a given
PID exists.
.PP
The
.I 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:
.PP
.in +4n
.EX
union sigval {
int sival_int;
void *sival_ptr;
};
.EE
.in
.PP
If the receiving process has installed a handler for this signal using the
.B SA_SIGINFO
flag to
.BR sigaction (2),
then it can obtain this data via the
.I si_value
field of the
.I siginfo_t
structure passed as the second argument to the handler.
Furthermore, the
.I si_code
field of that structure will be set to
.BR SI_QUEUE .
.SH RETURN VALUE
On success,
.BR sigqueue ()
returns 0, indicating that the signal was successfully
queued to the receiving process.
Otherwise, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EAGAIN
The limit of signals which may be queued has been reached.
(See
.BR signal (7)
for further information.)
.TP
.B EINVAL
.I sig
was invalid.
.TP
.B EPERM
The process does not have permission to send the signal
to the receiving process.
For the required permissions, see
.BR kill (2).
.TP
.B ESRCH
No process has a PID matching
.IR pid .
.SH VERSIONS
.BR sigqueue ()
and the underlying
.BR rt_sigqueueinfo ()
system call first appeared in Linux 2.2.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface Attribute Value
T{
.BR sigqueue ()
T} Thread safety MT-Safe
.TE
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH 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
.BR sigwait (3)),
then at least some signal must be delivered to this thread before this
function returns.
.SS C library/kernel differences
On Linux,
.BR sigqueue ()
is implemented using the
.BR rt_sigqueueinfo (2)
system call.
The system call differs in its third argument, which is the
.I siginfo_t
structure that will be supplied to the receiving process's
signal handler or returned by the receiving process's
.BR sigtimedwait (2)
call.
Inside the glibc
.BR sigqueue ()
wrapper, this argument,
.IR uinfo ,
is initialized as follows:
.PP
.in +4n
.EX
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() */
.EE
.in
.SH SEE ALSO
.BR kill (2),
.BR rt_sigqueueinfo (2),
.BR sigaction (2),
.BR signal (2),
.BR pthread_sigqueue (3),
.BR sigwait (3),
.BR signal (7)
.SH COLOPHON
This page is part of release 5.09 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
|
