.\" Copyright (C) 2014 Michael Kerrisk .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .TH uselocale 3 2024-05-02 "Linux man-pages 6.8" .SH NAME uselocale \- set/get the locale for the calling thread .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .P .BI "locale_t uselocale(locale_t " newloc ); .fi .P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .P .BR uselocale (): .nf Since glibc 2.10: _XOPEN_SOURCE >= 700 Before glibc 2.10: _GNU_SOURCE .fi .SH DESCRIPTION The .BR uselocale () function sets the current locale for the calling thread, and returns the thread's previously current locale. After a successful call to .BR uselocale (), any calls by this thread to functions that depend on the locale will operate as though the locale has been set to .IR newloc . .P The .I newloc argument can have one of the following values: .TP A handle returned by a call to \fBnewlocale\fP(3) or \fBduplocale\fP(3) The calling thread's current locale is set to the specified locale. .TP The special locale object handle \fBLC_GLOBAL_LOCALE\fP The calling thread's current locale is set to the global locale determined by .BR setlocale (3). .TP .I "(locale_t) 0" The calling thread's current locale is left unchanged (and the current locale is returned as the function result). .SH RETURN VALUE On success, .BR uselocale () returns the locale handle that was set by the previous call to .BR uselocale () in this thread, or .B LC_GLOBAL_LOCALE if there was no such previous call. On error, it returns .IR "(locale_t)\ 0" , and sets .I errno to indicate the error. .SH ERRORS .TP .B EINVAL .I newloc does not refer to a valid locale object. .SH STANDARDS POSIX.1-2008. .SH HISTORY glibc 2.3. POSIX.1-2008. .SH NOTES Unlike .BR setlocale (3), .BR uselocale () does not allow selective replacement of individual locale categories. To employ a locale that differs in only a few categories from the current locale, use calls to .BR duplocale (3) and .BR newlocale (3) to obtain a locale object equivalent to the current locale and modify the desired categories in that object. .SH EXAMPLES See .BR newlocale (3) and .BR duplocale (3). .SH SEE ALSO .BR locale (1), .BR duplocale (3), .BR freelocale (3), .BR newlocale (3), .BR setlocale (3), .BR locale (5), .BR locale (7)