NAME    [Toc]    [Back]

     sem_post -- increment (unlock) a semaphore

LIBRARY    [Toc]    [Back]

     Reentrant C Library (libc_r, -lc_r)

SYNOPSIS    [Toc]    [Back]

     #include <semaphore.h>

     int
     sem_post(sem_t *sem);

DESCRIPTION    [Toc]    [Back]

     The sem_post() function increments (unlocks) the semaphore pointed to by
     sem.  If there are threads blocked on the semaphore when sem_post() is
     called, then the highest priority thread that has been blocked the longest
 on the semaphore will be allowed to return from sem_wait().

     The sem_post() function is signal-reentrant and may be called within signal
 handlers.

RETURN VALUES    [Toc]    [Back]

     The sem_post() 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    [Toc]    [Back]

     The sem_post() function will fail if:

     [EINVAL]		sem points to an invalid semaphore.

SEE ALSO    [Toc]    [Back]

     sem_trywait(3), sem_wait(3), sem(4)

STANDARDS    [Toc]    [Back]

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


FreeBSD 5.2.1		       February 15, 2000		 FreeBSD 5.2.1