3:sem post

From Linux Man Pages

      sem_post - unlock a semaphore
      

Contents 1 SYNOPSIS 2 DESCRIPTION 3 RETURN VALUE 4 ERRORS 5 CONFORMING TO 6 NOTES 7 RELATED 8 CATEGORY

SYNOPSIS

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

DESCRIPTION

      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.

RETURN VALUE

      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.

ERRORS

      EINVAL sem is not a valid semaphore.

CONFORMING TO

      POSIX.1-2001.

NOTES

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

RELATED

      sem_getvalue(3), sem_wait(3), sem_overview(7)

CATEGORY