NAME

pthread_once —

dynamic package initialization

LIBRARY

POSIX Threads Library (libpthread, -lpthread)

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 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.

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

The pthread_once() function conforms to ISO/IEC 9945-1:1996 (“POSIX.1”).