std::messages::open,std::messages::do_open(3)

NAME
std::messages::open,std::messages::do_open - std::messages::open,std::messages::do_open

Synopsis
   Defined in header <locale>
   public:
   catalog open( const std::basic_string<char>& name, const std::locale& loc ) (1)
   const;
   protected:
   virtual catalog do_open( const std::basic_string<char>& name, const (2)
   std::locale& loc ) const;
   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
          a locale object that provides additional facets that may be required to read
   loc - 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 Übereinstimmung
 "Memory exhausted" in German: Speicher erschöpft

See also