Provided by: glibc-doc_2.27-3ubuntu1_all
pthread_once - once-only 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 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.
pthread_once always returns 0.
Xavier Leroy <Xavier.Leroy@inria.fr> LinuxThreads PTHREAD_ONCE(3)