NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
SEM_GETVALUE(3) Linux Programmer's Manual SEM_GETVALUE(3)
sem_getvalue - get the value of a semaphore
#include <semaphore.h>
int sem_getvalue(sem_t *sem, int *sval);
Link with -lrt or -pthread.
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.1-2001 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.
sem_getvalue() returns 0 on success; on error, -1 is returned and errno is set
to indicate the error.
EINVAL sem is not a valid semaphore.
POSIX.1-2001.
The value of the semaphore may already have changed by the time sem_getvalue()
returns.
sem_post(3), sem_wait(3), sem_overview(7)
This page is part of release 3.23 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/.
Linux 2006-03-25 SEM_GETVALUE(3)