std::messag...es::do_open(3)

💅 std::messag...es::do_open(3) 💅

okay bestie, this page is from the C++ Standard Libary manual — yes, that's the manual name, spelling and all — and it's about std::messages::open and std::messages::do_open. We're opening message catalogs and being cute about it. Buckle up. ✨

🌸 NAME 🌸

std::messages::open,std::messages::do_open — std::messages::open,std::messages::do_open.

That's the whole name block, bestie. It literally says both names, and we're not editing that. 💅

🦋 Synopsis 🦋

Defined in header <locale>, and here's the official little lineup:

public:
catalog open( const std::basic_string<char>& name, const std::locale& loc ) const;     (1)
protected:
virtual catalog do_open( const std::basic_string<char>& name, const std::locale& loc ) const;     (2)

1. (1) — Public member function, calls the protected virtual member function do_open of the most derived class.
2. (2) — Obtains a value of type catalog (inherited from std::messages_base), which can be passed to get() to retrieve messages from the message catalog named by name. This value is usable until passed to close().

🎀 Parameters 🎀

• name — name of the message catalog to open. Yes, the catalog's name. Iconic.
• loc — a locale object that provides additional facets that may be required to read messages from the catalog, such as std::codecvt to perform wide/multibyte conversions. She's the vibe provider for catalog reading. 💅

💖 Return value 💖

The non-negative value of type catalog that can be used with get() and close(). Returns a negative value if the catalog could not be opened.

So: non-negative = slay, negative = could not open. No cap. 💖

🔥 Notes 🔥

On POSIX systems, this function call usually translates to a call to catopen(). In GNU libstdc++, it calls textdomain.

The actual catalog location is implementation-defined, bestie. For the catalog "sed" (message catalogs installed with the Unix utility 'sed') in German locale, for example, the file opened by this function call may be:

• /usr/lib/nls/msg/de_DE/sed.cat
• /usr/lib/locale/de_DE/LC_MESSAGES/sed.cat
• /usr/share/locale/de/LC_MESSAGES/sed.mo

🌈 Example 🌈

The following example demonstrated retrieval of messages: on a typical GNU/Linux system it reads from /usr/share/locale/de/LC_MESSAGES/sed.mo.

// Run this code

#include <iostream>
#include <locale>

int main()
{
    std::locale loc("de_DE.utf8");
    std::cout.imbue(loc);
    auto& facet = std::use_facet<std::messages<char>>(loc);
    auto cat = facet.open("sed", loc);
    if (cat < 0)
        std::cout << "Could not open german \"sed\" message catalog\n";
    else
        std::cout << "\"No match\" in German: "
                  << facet.get(cat, 0, 0, "No match") << '\n'
                  << "\"Memory exhausted\" in German: "
                  << facet.get(cat, 0, 0, "Memory exhausted") << '\n';
    facet.close(cat);
}

💜 Possible output 💜

"No match" in German: Keine Übereinstimmung
"Memory exhausted" in German: Speicher erschöpft

🔗 See also 🔗

There aren't any extra cross-references listed on this page, bestie — the only thing hanging out at the bottom is the footer, and I'm giving that its own cute moment in the sign-off. 🫶

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💖 that's the whole page, bestie! The footer says the source/version is http://cppreference.com, dated 2024.06.10, and the page is std::messag...es::do_open(3). Periodt. 🫶✨