SEM_POST(3) BSD 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().
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 indi-
cate 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'').
BSD
January 22, 2003 BSD
