sem_acquire Acquire a semaphore &reftitle.description; boolsem_acquire resourcesem_identifier boolnowait&false; sem_acquire by default blocks (if necessary) until the semaphore can be acquired. A process attempting to acquire a semaphore which it has already acquired will block forever if acquiring the semaphore would cause its maximum number of semaphore to be exceeded. After processing a request, any semaphores acquired by the process but not explicitly released will be released automatically and a warning will be generated. &reftitle.parameters; sem_identifier sem_identifier is a semaphore resource, obtained from sem_get. nowait Specifies if the process shouldn't wait for the semaphore to be acquired. If set to true, the call will return false immediately if a semaphore cannot be immediately acquired. &reftitle.returnvalues; &return.success; &reftitle.changelog; &Version; &Description; 5.6.1 The $nowait parameter was added. &reftitle.seealso; sem_get sem_release