|
|
HP-UX Reference > Ssem_init(2)HP-UX 11i Version 2: December 2007 Update |
|
NAMEsem_init() — initialize an unnamed POSIX semaphore DESCRIPTIONsem_init() is used to initialize an unnamed semaphore. A successful call to sem_init() will create a new unnamed semaphore referred to by sem, if one does not exist, initialize the unnamed semaphore descriptor, referred to by sem, to the non-negative value specified by value. If the unnamed semaphore already exists, i.e. created by a previous call to sem_init(), it is re-initialized only if its current value is equal to its initial value (set by the last successful call to sem_init()). If so, the initial value of the unnamed semaphore is re-initialized to the value argument. Otherwise, the call fails. The argument pshared specifies if the unnamed semaphore is sharable with other processes. If pshared is equal to 0, the unnamed semaphore is not shared with other processes. If pshared is non-zero, the unnamed semaphore is sharable with any processes that can access sem. The access mode specified for the unnamed semaphore allows read and write permissions to all processes. If the calling process may attach to the shared sem_t structure, it is assumed it may operate on the 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_init() will create a new unnamed semaphore referred to by sem, if one does not exist, initialize the unnamed semaphore descriptor, referred to by sem, to the non-negative value specified by value. sem_init(sem, pshared, value); RETURN VALUEIf the semaphore was created and initialized, sem_init() returns 0 to the caller. If the semaphore could not be created/initialized, the call returns -1 and sets errno to indicate the error. ERRORSsem_init() fails and does not perform the requested operation if any of the following conditions are encountered:
|
|