catopen(3)

💬 catopen(3) — the catopen + catclose manual page, bestie edition

okay so this is a page from the Library Functions Manual, and it's all about opening and closing message catalogs 📚✨ yes, the thing that makes your program speak seventeen languages instead of just C.

---

✨ NAME ✨

catopen, catclose — open/close a message catalog 💖

📦 LIBRARY 📦

Standard C library (libc, -lc) 🫶

🧚 SYNOPSIS 🧚

#include <nl_types.h>

nl_catd catopen(const char *name, int flag);
int catclose(nl_catd catalog);

🌸 DESCRIPTION 🌸

So catopen() opens a message catalog and hands you back a catalog descriptor. That descriptor stays valid until you call catclose() or until execve(2) happens — whichever comes first, no cap. And btw, if a file descriptor is what's implementing your catalog descriptors, then the FD_CLOEXEC flag gets set. noted. 💅

Now the name argument — it specifies the name of the message catalog that's gonna be opened. Here's the vibe check:

• if name is an absolute path (like, it literally contains a /), then name is the pathname of the message catalog. simple as that.
• otherwise, the environment variable NLSPATH gets used, with name substituted in for %N (peep locale(7) for the deets).

⚠️ it is unspecified whether NLSPATH will be used when the process has root privileges. so like… don't build your whole personality on it, bestie.

If NLSPATH doesn't exist in the environment, or if a message catalog can't be opened in any of the paths it specifies, then an implementation defined path is used. and this default path? it may depend on the LC_MESSAGES locale setting when the flag argument is NL_CAT_LOCALE, and on the LANG environment variable when the flag argument is 0. 😭

🚨 changing the LC_MESSAGES part of the locale may invalidate open catalog descriptors. like, they're just gone. bye.

The flag argument to catopen() tells you where the language is coming from:

• if it's set to NL_CAT_LOCALE, it uses the current locale setting for LC_MESSAGES 🌍
• otherwise, it uses the LANG environment variable

And catclose()? It closes the message catalog identified by catalog. It invalidates any subsequent references to the message catalog defined by catalog — meaning after this, referencing it is giving absolutely nothing. 💀

🎀 RETURN VALUE 🎀

catopen() returns a message catalog descriptor of type nl_catd on success. slay. 🎉

On failure, it returns (nl_catd) -1 and sets errno to indicate the error. The possible error values include all possible values for the open(2) call — so like, the whole menu, not just a few. 🍓

catclose() returns 0 on success, or -1 on failure.

🌈 ENVIRONMENT 🌈

• LC_MESSAGES — may be the source of the LC_MESSAGES locale setting, and thus determine the language to use if flag is set to NL_CAT_LOCALE. 👑
• LANG — the language to use if flag is 0.

🔥 ATTRIBUTES 🔥

for an explanation of the terms used in this section, go look at attributes(7) — iykyk.

• catopen() — Thread safety: MT-Safe env ✨
• catclose() — Thread safety: MT-Safe ✨

🦋 VERSIONS 🦋

The above is the POSIX.1 description. The glibc value for NL_CAT_LOCALE is 1. The default path varies, but usually looks at a number of places below /usr/share/locale. 👀

⭐ STANDARDS ⭐

POSIX.1-2008.

💜 HISTORY 💜

POSIX.1-2001.

🌟 SEE ALSO 🌟

catgets(3), setlocale(3)

---

and that's the whole page, bestie!! this one came from the Linux man-pages 6.20, dated 2026-02-08, and it's literally the catopen(3) page 💖 go open a catalog, you've got this 🫶✨