Name
sem_getvalue — get the value of a semaphore
Synopsis
#include <semaphore.h>
int
sem_getvalue( |
sem_t *restrict sem, |
int *restrict sval); |
![[Note]](../stylesheet/note.png) |
Note |
|---|---|
|
Link with |
DESCRIPTION
sem_getvalue() places the
current value of the semaphore pointed to sem into the integer pointed to
by sval.
If one or more processes or threads are blocked waiting to
lock the semaphore with sem_wait(3), POSIX.1
permits two possibilities for the value returned in
sval: either 0 is
returned; or a negative number whose absolute value is the
count of the number of processes and threads currently
blocked in sem_wait(3). Linux adopts
the former behavior.
RETURN VALUE
sem_getvalue() returns 0 on
success; on error, −1 is returned and errno is set to indicate the error.
ERRORS
- EINVAL
-
semis not a valid semaphore. (The glibc implementation currently does not check whethersemis valid.)
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
sem_getvalue() |
Thread safety | MT-Safe |
COLOPHON
This page is part of release 5.11 of the Linux 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/.
|
Copyright (C) 2006 Michael Kerrisk <mtk.manpagesgmail.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 Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date.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 |