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SEM_POST(3)                Library Functions Manual                SEM_POST(3)

NAME
     sem_post -- increment (unlock) a semaphore

LIBRARY
     POSIX Real-time Library (librt, -lrt)

SYNOPSIS
     #include <semaphore.h>

     int
     sem_post(sem_t *sem);

DESCRIPTION
     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() or
     sem_timedwait().

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

RETURN VALUES
     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
     sem_post() will fail if:

     [EINVAL]           sem points to an invalid semaphore.

SEE ALSO
     sem_timedwait(3), sem_trywait(3), sem_wait(3)

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

NetBSD 7.1.2                   February 29, 2012                  NetBSD 7.1.2