2 .\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
4 .\" %%%LICENSE_START(VERBATIM)
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
26 .TH SEM_GETVALUE 3 2017-09-15 "Linux" "Linux Programmer's Manual"
28 sem_getvalue \- get the value of a semaphore
31 .B #include <semaphore.h>
33 .BI "int sem_getvalue(sem_t *" sem ", int *" sval );
36 Link with \fI\-pthread\fP.
39 places the current value of the semaphore pointed to
41 into the integer pointed to by
44 If one or more processes or threads are blocked
45 waiting to lock the semaphore with
47 POSIX.1 permits two possibilities for the value returned in
50 or a negative number whose absolute value is the count
51 of the number of processes and threads currently blocked in
53 Linux adopts the former behavior.
57 on error, \-1 is returned and
59 is set to indicate the error.
64 is not a valid semaphore.
66 For an explanation of the terms used in this section, see
72 Interface Attribute Value
75 T} Thread safety MT-Safe
78 POSIX.1-2001, POSIX.1-2008.
80 The value of the semaphore may already have changed by the time