check_language_code

Check if a given string contains a known ISO 639 language code.

This is useful in situations where it's not clear whether a given string is a language code (which should be put into a LANGUAGE_CODE tag) or a free-form language name descriptor (which should be put into a LANGUAGE_NAME tag instead).

Parameters:

lang_code

ISO-639 language code (e.g. "deu" or "ger" or "de")

Returns:

TRUE if the two- or three-letter language code in lang_code is a valid ISO-639 language code.