sem_post(3) Library Functions Manual sem_post(3) NAME sem_post - unlock a semaphore LIBRARY POSIX threads library (libpthread, -lpthread) 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 an- other 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 er- ror. ERRORS EINVAL sem is not a valid semaphore. EOVERFLOW The maximum allowable value for a semaphore would be exceeded. ATTRIBUTES For an explanation of the terms used in this section, see at- tributes(7). ┌────────────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├────────────────────────────────────────────┼───────────────┼─────────┤ │sem_post() │ Thread safety │ MT-Safe │ └────────────────────────────────────────────┴───────────────┴─────────┘ STANDARDS POSIX.1-2001. NOTES sem_post() is async-signal-safe: it may be safely called within a sig- nal handler. EXAMPLES See sem_wait(3) and shm_open(3). SEE ALSO sem_getvalue(3), sem_wait(3), sem_overview(7), signal-safety(7) Linux man-pages 6.03 2022-12-15 sem_post(3)
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