freebsd man page for sem_post

SEM_POST(3)						   BSD Library Functions Manual 					       SEM_POST(3)

NAME
     sem_post -- increment (unlock) a semaphore

LIBRARY
     Standard C Library (libc, -lc)

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().

     The sem_post() function 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 indi-
     cate the error.

ERRORS
     The sem_post() function will fail if:

     [EINVAL]		The sem argument points to an invalid semaphore.

     [EOVERFLOW]	The semaphore value would exceed SEM_VALUE_MAX.

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

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

BSD
								 January 28, 2015							       BSD