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.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH pthread_once 3 (date) "Linux man-pages (unreleased)"
.
.
.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 ", typeof(void (void)) *" init_routine ;
.
.
.SH DESCRIPTION
The purpose of
.BR pthread_once ()
is
to ensure that a piece of initialization code is executed at most once.
The
.I once_control
argument points to a static or extern variable
statically initialized to
.BR PTHREAD_ONCE_INIT .
.P
The first time
.BR pthread_once ()
is called
with a given
.I once_control
argument,
it calls
.I init_routine
with no argument
and changes the value of the
.I once_control
variable
to record that initialization has been performed.
Subsequent calls to
.BR pthread_once ()
with the same
.I once_control
argument
do nothing.
.
.
.SH "RETURN VALUE"
.BR pthread_once ()
always returns 0.
.
.
.SH ERRORS
None.
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