Manpages - sem_post.3

sem_post - unlock a semaphore

  #include <semaphore.h>

  int sem_post(sem_t *sem);

Link with -pthread.

*sem_post*() increments (unlocks) the semaphore pointed to by sem. If the semaphore’s value consequently becomes greater than zero, then another process or thread blocked in a *sem_wait*(3) call will be woken up and proceed to lock the semaphore.

*sem_post*() returns 0 on success; on error, the value of the semaphore is left unchanged, -1 is returned, and errno is set to indicate the error.

EINVAL

sem is not a valid semaphore.

EOVERFLOW

The maximum allowable value for a semaphore would be exceeded.

For an explanation of the terms used in this section, see *attributes*(7).

POSIX.1-2001.

*sem_post*() is async-signal-safe: it may be safely called within a signal handler.

See *sem_wait*(3) and *shm_open*(3).

*sem_getvalue*(3), *sem_wait*(3), *sem_overview*(7), *signal-safety*(7)

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