osx man page for sem_post

SEM_POST(2)						      BSD System Calls Manual						       SEM_POST(2)

NAME
     sem_post -- unlock a semaphore

SYNOPSIS
     #include <semaphore.h>

     int
     sem_post(sem_t *sem);

DESCRIPTION
     The semaphore referenced by sem is unlocked, the value of the semaphore is incremented, and all threads which are waiting on the semaphore
     are awakened.

     sem_post() is reentrant with respect to signals and may be called from within a signal hanlder.

     If successful, sem_post() will return 0.  Otherwise, -1 is returned and errno is set.

ERRORS
     sem_post() succeeds unless:

     [EINVAL]		sem is not a valid semaphore descriptor.

SEE ALSO
     sem_open(2), sem_trywait(2), sem_wait(2), semctl(2), semget(2), semop(2)

HISTORY
     sem_post() is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).

Darwin								   June 8, 2000 							    Darwin