The nl_langinfo function returns a pointer to a string containing information relevant to the particular language or cultural area defined in the programs locale. The manifest constant names and values of item are defined in
.In langinfo.h .
Calls to setlocale with a category corresponding to the category of item, or to the category LC_ALL, may overwrite buffer pointed by the return value.
In a locale where langinfo data is not defined, nl_langinfo returns a pointer to the corresponding string in the POSIX locale. In all locales, nl_langinfo returns a pointer to an empty string if item contains an invalid setting.
would return a pointer to the string "Dom" if the identified language was Portuguese, and "Sun" if the identified language was English.