SEM_POST(3) NetBSD Library Functions Manual SEM_POST(3)
sem_post -- increment (unlock) a semaphore
POSIX Real-time Library (librt, -lrt)
#include <semaphore.h> int sem_post(sem_t *sem);
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 long- est 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.
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.
sem_post() will fail if: [EINVAL] sem points to an invalid semaphore.
sem_timedwait(3), sem_trywait(3), sem_wait(3)
sem_post() conforms to ISO/IEC 9945-1:1996 (``POSIX.1''). NetBSD 8.1 February 29, 2012 NetBSD 8.1
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