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pthread_once(3) — Linux manual page

pthread_once(3)          Library Functions Manualpthread_once(3)

NAME        top

       pthread_once - once-only initialization

SYNOPSIS        top

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

DESCRIPTION        top

       The purpose ofpthread_once() is to ensure that a piece of       initialization code is executed at most once.  Theonce_control       argument points to a static or extern variable statically       initialized toPTHREAD_ONCE_INIT.       The first timepthread_once() is called with a givenonce_control       argument, it callsinit_routine with no argument and changes the       value of theonce_control variable to record that initialization       has been performed.  Subsequent calls topthread_once() with the       sameonce_control argument do nothing.

RETURN VALUE        top

pthread_once() always returns 0.

ERRORS        top

       None.

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17pthread_once(3)

Pages that refer to this page:pthreads(7)

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