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sem_post(3) Library Functions Manual sem_post(3)
sem_post - unlock a semaphore
POSIX threads library (libpthread, -lpthread)
#include <semaphore.h> int sem_post(sem_t *sem);
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). ┌─────────────────────────────────────┬───────────────┬─────────┐ │ Interface │ Attribute │ Value │ ├─────────────────────────────────────┼───────────────┼─────────┤ │ sem_post() │ Thread safety │ MT-Safe │ └─────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
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)
Linux man-pages (unreleased) (date) sem_post(3)
Pages that refer to this page: sem_close(3), sem_destroy(3), sem_getvalue(3), sem_init(3), sem_open(3), sem_timedwait(3p), sem_unlink(3), sem_wait(3), sem_overview(7), signal-safety(7)