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.\" Copyright, Xavier Leroy <Xavier.Leroy@inria.fr>
.\" Copyright 2023, Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH pthread_once 3 2023-10-31 "Linux man-pages 6.7"
.
.
.SH NAME
pthread_once
\-
once-only initialization
.
.
.SH SYNOPSIS
.B #include <pthread.h>
.P
.BI "pthread_once_t " once_control " = PTHREAD_ONCE_INIT;"
.P
.BI "int pthread_once(pthread_once_t *" once_control ", void (*" init_routine ") (void));"
.
.
.SH DESCRIPTION
The purpose of \fBpthread_once\fP is
to ensure that a piece of initialization code is executed at most once.
The \fIonce_control\fP argument points to a static or extern variable
statically initialized to \fBPTHREAD_ONCE_INIT\fP.
.P
The first time \fBpthread_once\fP is called
with a given \fIonce_control\fP argument,
it calls \fIinit_routine\fP with no argument
and changes the value of the \fIonce_control\fP variable
to record that initialization has been performed.
Subsequent calls to \fBpthread_once\fP
with the same \fBonce_control\fP argument
do nothing.
.
.
.SH "RETURN VALUE"
\fBpthread_once\fP always returns 0.
.
.
.SH ERRORS
None.
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