centos man page for sem_getvalue

SEM_GETVALUE(3) 					     Linux Programmer's Manual						   SEM_GETVALUE(3)

NAME
       sem_getvalue - get the value of a semaphore

SYNOPSIS
       #include <semaphore.h>

       int sem_getvalue(sem_t *sem, int *sval);

       Link with -pthread.

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.1-2001 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.

RETURN VALUE
       sem_getvalue() returns 0 on success; on error, -1 is returned and errno is set to indicate the error.

ERRORS
       EINVAL sem is not a valid semaphore.

CONFORMING TO
       POSIX.1-2001.

NOTES
       The value of the semaphore may already have changed by the time sem_getvalue() returns.

SEE ALSO
       sem_post(3), sem_wait(3), sem_overview(7)

COLOPHON
       This  page is part of release 3.53 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								    2012-05-13							   SEM_GETVALUE(3)