NL_LANGINFO(3POSIX)

💖 nl_langinfo — the POSIX girlies' guide 💖

okay bestie, so this one is from the POSIX Programmer's Manual — that's the manual name, she's fancy 💅

⚠️ real talk before we start: this page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so go check the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface may not be implemented on Linux at all. Not every baddie makes it to every platform, iykyk 😭

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🌸 PROLOG 🌸

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details on Linux behavior), or the interface may not be implemented on Linux.

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✨ NAME ✨

nl_langinfo, nl_langinfo_l — language information 🗣️💬

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🎀 SYNOPSIS 🎀

#include <langinfo.h>

char *nl_langinfo(nl_item item);
char *nl_langinfo_l(nl_item item, locale_t locale);

like... two functions, one vibe check, and they want all the language tea 🫖

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💅 DESCRIPTION 💅

So nl_langinfo() and nl_langinfo_l() shall return a pointer to a string holding info relevant to the particular language or cultural area defined in the current locale, or in the locale represented by locale, respectively (peep <langinfo.h> for more 👀). The manifest constant names and values of item are defined in <langinfo.h>. For example:

nl_langinfo(ABDAY_1)

would return a pointer to the string "Dom" if the identified language was Portuguese, and "Sun" if the identified language was English. iconic behavior fr 🌞

nl_langinfo_l(ABDAY_1, loc)

would return a pointer to the string "Dom" if the identified language of the locale represented by loc was Portuguese, and "Sun" if the identified language of the locale represented by loc was English.

Not me needing to tell you this: the nl_langinfo() function need not be thread-safe. She's not the one holding the group together, she's just vibing 😭

🚨 and the behavior is undefined if the locale argument to nl_langinfo_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle. That's not a cute little oopsie bestie, that's undefined behavior. Do not pass her a fake ID 💀

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🌈 RETURN VALUE 🌈

In a locale where langinfo data is not defined, these functions shall return a pointer to the corresponding string in the POSIX locale. In all locales, these functions shall return a pointer to an empty string if item contains an invalid setting. okay empty string, she said "no thoughts, head empty" 🎈

The application shall not modify the string returned. Not yours. Don't touch. Hands off 🙅

The pointer returned by nl_langinfo() might be invalidated, or the string content might be overwritten, by:

• a subsequent call to nl_langinfo() in any thread, or to nl_langinfo_l() in the same thread or the initial thread
• subsequent calls to setlocale() with a category corresponding to the category of item (see <langinfo.h>) or the category LC_ALL
• subsequent calls to uselocale() which change the category corresponding to the category of item

The pointer returned by nl_langinfo_l() might be invalidated, or the string content might be overwritten, by:

• a subsequent call to nl_langinfo_l() in the same thread, or to nl_langinfo() in any thread
• subsequent calls to freelocale() or newlocale() which free or modify the locale object that was passed to nl_langinfo_l()

The returned pointer and the string content might also be invalidated if the calling thread is terminated. so like... if the thread dips, so does your pointer. tragic 💀🦋

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💜 ERRORS 💜

No errors are defined. (she's unbothered, moisturized, in her lane ✨)

The following sections are informative.

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🍓 EXAMPLES 🍓

Getting Date and Time Formatting Information ⏰

The following example returns a pointer to a string containing date and time formatting information, as defined in the LC_TIME category of the current locale.

#include <time.h>
#include <langinfo.h>
...
strftime(datestring, sizeof(datestring), nl_langinfo(D_T_FMT), tm);
...

look at her, getting her D_T_FMT straight into strftime like a main character 💅

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🧚 APPLICATION USAGE 🧚

The array pointed to by the return value should not be modified by the program, but may be modified by further calls to these functions. yes bestie, she said "I'm not yours, I'm the streets' 🚶♀️"

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👑 RATIONALE 👑

ngl this part is lowkey the juiciest. The possible interactions between internal data used by nl_langinfo() and nl_langinfo_l() are complicated by the fact that nl_langinfo_l() must be thread-safe but nl_langinfo() need not be. The various implementation choices are:

1. nl_langinfo_l() and nl_langinfo() use separate buffers, or at least one of them does not use an internal string buffer. In this case there are no interactions. clean. no drama. we love her 🫶
2. nl_langinfo_l() and nl_langinfo() share an internal per-thread buffer. There can be interactions, but only in the same thread.
3. nl_langinfo_l() uses an internal per-thread buffer, and nl_langinfo() uses (in all threads) the same buffer that nl_langinfo_l() uses in the initial thread. There can be interactions, but only when nl_langinfo_l() is called in the initial thread.

so basically: pick your fighter, but the vibes are defined either way 💀✨

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🔥 FUTURE DIRECTIONS 🔥

None. she said "I'm done evolving, I'm already that girl" 💅 periodt

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⭐ SEE ALSO ⭐

• setlocale()
• uselocale()

The Base Definitions volume of POSIX.1‐2017, Chapter 7, Locale, <langinfo.h>, <locale.h>, <nl_types.h>

go read those, bestie, I believe in you 📚🦋

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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. 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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and that's the whole page, bestie 💖 she's from IEEE/The Open Group, 2017 — the NL_LANGINFO(3POSIX) girlies stay winning, mwah 🎀✨