|SEM_POST(3)||Linux Programmer's Manual||SEM_POST(3)|
NAMEsem_post - unlock a semaphore
int sem_post(sem_t * sem );
DESCRIPTIONsem_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 VALUEsem_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.
- sem is not a valid semaphore.
- The maximum allowable value for a semaphore would be exceeded.
NOTESsem_post() is async-signal-safe: it may be safely called within a signal handler.
SEE ALSOsem_getvalue(3), sem_wait(3), sem_overview(7)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.