What environment variable indicates the user's preferred language in Linux?

The environment variable that indicates the user's preferred language in Linux is LANG. This variable is a key part of the locale settings and defines the default locale that the system should use for various operations, including sorting, formatting dates, and displaying messages.

When a user sets the LANG variable, it typically determines the primary language, as well as other regional settings like character encoding and other locale-related data. For instance, if a user sets LANG to "en_US.UTF-8", it indicates that American English with UTF-8 character encoding is preferred.

While other choices relate to language and locale settings, LANG specifically serves as the foundational variable from which other locale categories are derived. LC_ALL is a variable that can override all other LC_* variables but does not represent a preferred language by itself; it is used to set the locale for all categories simultaneously. LANGUAGE is another variable that provides a list of preferred languages, but it is less commonly used in basic locale settings. LC_MESSAGES specifically handles message localization, ensuring that system messages are displayed in the user's preferred language, but it depends on the LANG variable for its default setting.

Thus, LANG serves as the primary indicator of the user's language preference in the Linux environment.