pthread_once - once-only initialization

       The  purpose  of  pthread_once is to ensure that a piece of initialization code is executed at most once.
       The  once_control  argument  points  to  a  static  or  extern   variable   statically   initialized   to
       PTHREAD_ONCE_INIT.

       The  first  time pthread_once is called with a given once_control argument, it calls init_routine with no
       argument and changes the value of the once_control  variable  to  record  that  initialization  has  been
       performed.  Subsequent calls to pthread_once with the same once_control argument do nothing.

       None.

Linux man-pages 6.9.1                              2024-05-02                                    pthread_once(3)

       pthread_once - once-only initialization

pthread_once always returns 0.

#include<pthread.h>pthread_once_tonce_control=PTHREAD_ONCE_INIT;intpthread_once(pthread_once_t*once_control,void(*init_routine)(void));