std::messages::open, std::messages::do_open

C++

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Named requirements

Language support library

Concepts library (C++20)

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Utilities library

Strings library

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Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

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Technical Specifications

Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME

std::messages

Member functions

messages::messages

messages::~messages

messages::openmessages::do_open

messages::getmessages::do_get

messages::closemessages::do_close

Defined in header <locale>
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) Public member function, calls the protected virtual member function do_open of the most derived class.

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
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

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.

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: 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, or /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 bereinstimmung
"Memory exhausted" in German: Speicher erschpft