10.4 Using the setlocale Function to Set Up an International Environment

An application sets up its international environment at run-time by calling the setlocale function. The international environment is set up in one of two ways:

• The environment is defined by one locale. In this case, each of the locale categories is defined by the same locale.

• Categories are defined separately. This lets you define a mixed environment that uses different locales depending on the operation performed. For example, if an English user has some Spanish files that are to be processed by an application, the LC_COLLATE category could be defined by a Spanish locale while the other categories are defined by an English locale. To do this you would call setlocale once for each category.

The syntax for the setlocale function is:

char *setlocale(int category, const char *locale)

Where:

• category is either the name of a category, or LC_ ALL. Specifying LC_ALL means that all the categories are defined by the same locale. Specify a category name to set up a mixed environment.

• locale is one of the following:

  • The name of the locale to use.

    If you want users to specify the locale interactively, your application could prompt the user for a locale name, and then pass the name as an argument to the setlocale function. A locale name has the following format:

       language_country.codeset[@modifier]
    

    For example, setlocale(LC_COLLATE, "en_US.ISO8859-1") selects the locale en_US.ISO8859-1 for the LC_COLLATE category.

  • ""

    This causes the function to use logical names to determine the locale for the category specified. See Specifying the Locale Using Logical Names for details.

If an application does not call the setlocale function, the default locale is the C locale. This allows such applications to call those functions that use information in the current locale.

Specifying the Locale Using Logical Names

If the setlocale function is called with "" as the locale argument, the function checks for a number of logical names to determine the locale name for the category specified.

There are a number of logical names that users can set up to define their international environment:

• Logical name corresponding to a category

  For example, the LC_NUMERIC logical name defines the locale associated with the LC_NUMERIC category within the user's environment.

• LC_ALL

• LANG

  The LANG logical name defines the user's language.

In addition to the logical names defined by a user, there are a number of system-wide logical names, set up during system startup, that define the default international environment for all users on a system:

• SYS$category

  Where category is the name of a category. This specifies the system default for that category.

• SYS$LC_ALL

• SYS$LANG

The setlocale function checks for user-defined logical names first, and if these are not defined, it checks the system logical names.