PTHREAD_ONCE(3) Library Functions Manual PTHREAD_ONCE(3)

pthread_once — dynamic package initialisation

#include <pthread.h>

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

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 of 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 initialisation routine has been called.

The function pthread_once() is not a cancellation point. However, if is a cancellation point and is canceled, the effect on once_control is as if pthread_once() was never called.

The constant PTHREAD_ONCE_INIT is defined by the header <pthread.h>.

The behaviour of pthread_once() is undefined if once_control has automatic storage duration or is not initialised by PTHREAD_ONCE_INIT.

Upon successful completion, pthread_once() returns zero. Otherwise, an error number is returned to indicate the error.

No errors are defined.

The pthread_once() function will not return an error code of [EINTR].

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<pthread,h> .

Derived from the POSIX Threads Extension (1003.1c-1995)

February 1997 posix.fail