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Manual: sem_release
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sem_release

sem_release -- release a semaphore

Description

int sem_release(int sem_identifier);

Returns: true on success, false on error

sem_release() releases the semaphore if it is currently acquired by the calling process, otherwise a warning is generated.

After releasing the semaphore, sem_acquire() may be called to re-acquire it.

See also: sem_get() and sem_acquire().


 User Contributed Notes: sem_release

apua@communiplex.com
08-Dec-1999 02:54
 The fact that sem_release only resease the semaphore if it is currently acquired by the calling process is, in fact, a misfeature since sometimes (eg in a readers-writers implementation) it is desirable to release a semaphore acquired by another process. In C you can do that. I'm telling this because I was trying to write a chat app in php3 made of two programs: a listener and a speaker. The speaker releases a semaphore to inform that there is a new message in a shared memory var. And listeners wait in that semaphore before outputting the message.


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