pthread_once(3) BSD Library Functions Manual pthread_once(3)
pthread_once -- dynamic package initialization
#include <pthread.h> pthread_once_t once_control = PTHREAD_ONCE_INIT; int pthread_once(pthread_once_t *once_control, void (*init_routine)(void));
The first call to pthread_once() by any thread in a process, with a given once_control, will call the init_routine() with no arguments. Subsequent calls to pthread_once() with the same once_control will not call the init_routine(). On return from pthread_once(), it is guaranteed that init_routine() has completed. The once_control parameter is used to determine whether the associated initialization routine has been called. The function pthread_once() is not a cancellation point. However, if init_routine() is a cancellation point and is cancelled, the effect on once_control is as if pthread_once() was never called. The constant PTHREAD_ONCE_INIT is defined by header <pthread.h>. The behavior of pthread_once() is undefined if once_control has automatic storage duration or is not initialized by PTHREAD_ONCE_INIT.
If successful, the pthread_once() function will return zero. Otherwise, an error number will be returned to indicate the error.
pthread_once() conforms to ISO/IEC 9945-1:1996 (``POSIX.1''). BSD April 4, 1996 BSD
Mac OS X 10.8 - Generated Thu Aug 30 09:57:54 CDT 2012