sem_getvalue(3) [netbsd man page]

SEM_GETVALUE(3) 					   BSD Library Functions Manual 					   SEM_GETVALUE(3)

NAME

     sem_getvalue -- get the value of a semaphore

LIBRARY

     POSIX Real-time Library (librt, -lrt)

SYNOPSIS

     #include <semaphore.h>

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

DESCRIPTION

     The sem_getvalue() function sets the variable pointed to by sval to the current value of the semaphore pointed to by sem, as of the time that
     the call to sem_getvalue() is actually run.

RETURN VALUES

     The sem_getvalue() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to
     indicate the error.

ERRORS

     sem_getvalue() will fail if:

     [EINVAL]		sem points to an invalid semaphore.

SEE ALSO

     sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS

     sem_getvalue() conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').

     The value of the semaphore is never negative, even if there are threads blocked on the semaphore.	POSIX is somewhat ambiguous in its wording
     with regard to what the value of the semaphore should be if there are blocked waiting threads, but this behavior is conformant, given the
     wording of the specification.

BSD
								 January 22, 2003							       BSD

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 -lrt or -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 3.25 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)