DragonFly On-Line Manual Pages

SEM_POST(3)           DragonFly Library Functions Manual           SEM_POST(3)

NAME
     sem_post - increment (unlock) a semaphore

LIBRARY
     POSIX Threads Library (libpthread, -lpthread)

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().

     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_trywait(3), sem_wait(3)

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

DragonFly 5.9-DEVELOPMENT       April 15, 2009       DragonFly 5.9-DEVELOPMENT