setlocale/3

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Availability:built-in

setlocale(+Category, -Old, +New)

Set/Query the locale setting which tells the C library how to interpret text files, write numbers, dates, etc. Category is one of all, collate, ctype, messages, monetary, numeric or time. For details, please consult the C library locale documentation. See also section 2.19.1. Please note that the locale is shared between all threads and thread-safe usage of setlocale/3 is in general not possible. Do locale operations before starting threads or thoroughly study threading aspects of locale support in your environment before using in multithreaded environments. Locale settings are used by format_time/3, collation_key/2 and locale_sort/2.

The messages locale defines the language used by print_message/2. Note that this locale is not available on all operating system. Notably Windows does not support this category. See win_get_user_preferred_ui_languages/2.