|
|
HP-UX Reference > Ssem_getvalue(2)HP-UX 11i Version 2: December 2007 Update |
|
NAMEsem_getvalue() — get the value of a POSIX semaphore DESCRIPTIONsem_getvalue() is used to read the value of the semaphore. The value of the semaphore specified by sem is read, at some unspecified time during the call, and then stored into sval. If the semaphore value is <= 0, at that time, the semaphore is considered unavailable. If the semaphore value is > 0, at that time, the semaphore is considered available. If sval is positive, it is equal to the number of locks available on the semaphore, at the time the semaphore value was read. If sval is negative, its absolute value is equal to the number of blocked threads waiting for the semaphore to become available, at the time the semaphore value was read. If the specified semaphore referred to by sem is a named semaphore, then this semaphore must have been opened by the calling process with sem_open() and the process must have read permission on this semaphore. To use this function, link in the realtime library by specifying -lrt on the compiler or linker command line. EXAMPLESThe following call to sem_getvalue() will read the value of the semaphore sem and store it in sval. sem_getvalue(sem,sval); RETURN VALUEA successful call to sem_getvalue() will return 0. Otherwise, the call to sem_getvalue() will return -1 with errno set to the appropriate value of the error condition. |
|