sem_post — unlock a semaphore
(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.
sem is not a
The maximum allowable value for a semaphore would be exceeded.
For an explanation of the terms used in this section, see attributes(7).
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