Multithreaded Programming Guide

Increment a Semaphore


int	sem_post(sem_t *sem);
#include <semaphore.h>

sem_t sem;
int ret;

ret = sem_post(&sem); /* semaphore is posted */

Use sem_post(3R) to atomically increment the semaphore pointed to by sem. When any threads are blocked on the semaphore, one of them is unblocked. (For Solaris threads, see "sema_post(3T)".)

Return Values

sem_post() returns zero after completing successfully. Any other returned value indicates that an error occurred. When the following condition occurs, the function fails and returns the corresponding value.


sem points to an illegal address.