std::messages<CharT>::open, std::messages<CharT>::do_open

Header: <locale>

1. Public member function, calls the protected virtual member function do_open of the most derived class.

# Declarations

public:
catalog open( const std::string& name, const std::locale& loc ) const;

protected:
virtual catalog do_open( const std::string& name, const std::locale& loc ) const;

# 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

#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);
}