USELOCALE(3P)

💖 USELOCALE 💖

okay bestie, welcome to uselocale(3P) from the POSIX Programmer's Manual — yeah, the fancy IEEE/The Open Group one. it's giving ✨standards body✨ but make it cute. let's get into it 🫶

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🌸 PROLOG 🌸

okay so real talk first: this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (so like, go check the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface might not even be implemented on Linux at all. 🙈 not me warning you upfront, i'm just being a good friend.

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✨ NAME ✨

uselocale — use locale in current thread 👑

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🎀 SYNOPSIS 🎀

#include <locale.h>

locale_t uselocale(locale_t newloc);

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🦋 DESCRIPTION 🦋

so the uselocale() function shall set or query the current locale for the calling thread. that's it, that's the whole vibe. per-thread locale energy, no cap. 💅

the value for the newloc argument shall be one of the following, bestie:

1. a value returned by the newlocale() or duplocale() functions
2. the special locale object descriptor LC_GLOBAL_LOCALE
3. (locale_t)0

now let's break it down because this is the part that matters:

• if newloc is (locale_t)0, the current locale shall not be changed — this value is literally there so you can query the current locale setting. pure information-gathering, no side effects, love that for us.
• if newloc is LC_GLOBAL_LOCALE, any thread-local locale for the calling thread shall be uninstalled. the thread shall again use the global locale as the current locale, and changes to the global locale shall affect the thread. so you're rejoining the group chat, basically. 🌈
• otherwise, the locale represented by newloc shall be installed as a thread-local locale to be used as the current locale for the calling thread.

and once you've called uselocale() to install a thread-local locale, the behavior of every interface using data from the current locale shall be affected for the calling thread. every. single. one. 😭 but here's the iconic part: the current locale for other threads shall remain unchanged. main character thread only, everyone else stays unbothered. 💅

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🔥 RETURN VALUE 🔥

upon successful completion, uselocale() shall return a handle for the thread-local locale that was in use as the current locale for the calling thread on entry to the function — or LC_GLOBAL_LOCALE if no thread-local locale was in use.

otherwise, uselocale() shall return (locale_t)0 and set errno to indicate the error. sad girl hours. 😭

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💀 ERRORS 💀

the uselocale() function may fail if:

• EINVAL — newloc is not a valid locale object and is not (locale_t)0.

and just so you know, the following sections are informative. so like, cute to know, but not the binding part. 🫶

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🍓 EXAMPLES 🍓

None. yeah. nothing. empty. the void. 🙈

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🧚 APPLICATION USAGE 🧚

unlike the setlocale() function, the uselocale() function does not allow replacing some locale categories only. so if your application needs to install a locale that differs only in a few categories, you must use newlocale() to change a locale object equivalent to the currently used locale, and then install it. no shortcuts bestie, that's the assignment. ✨

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💜 RATIONALE 💜

None. iconic of them honestly.

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⭐ FUTURE DIRECTIONS ⭐

None. the future is... nothing? slay i guess. 💅

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🌈 SEE ALSO 🌈

• duplocale()
• freelocale()
• newlocale()
• setlocale()

the Base Definitions volume of POSIX.1‐2017, <locale.h> 📚

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👑 COPYRIGHT 👑

portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group.

in the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. 👀 (so if something looks off, the original wins, no arguments.)

the original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. to report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . 🐛

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okay that's the whole page bestie, you ate that 🫶 this was IEEE/The Open Group, 2017, and the page is USELOCALE(3P) — so go forth and set your thread-local locales, periodt. 💖✨🎀🦋