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PTHREAD_ONCE(3)          BSD Library Functions Manual          PTHREAD_ONCE(3)

NAME
     pthread_once -- dynamic package initialization

SYNOPSIS
     #include <pthread.h>

     pthread_once_t once_control = PTHREAD_ONCE_INIT;

     int
     pthread_once(pthread_once_t *once_control, void (*init_routine)(void));

DESCRIPTION
     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 rou-tine routine
     tine 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.

RETURN VALUES
     If successful, the pthread_once() function will return zero.  Otherwise, an error number will be
     returned to indicate the error.

ERRORS
     None.

STANDARDS
     pthread_once() conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').

BSD                              April 4, 1996                             BSD