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).