Which environment variable defines the character set to use for the Linux system?

The environment variable that defines the character set for the Linux system is LANG. This variable is responsible for determining the user's locale and influences how the system handles language, character encoding, formatting for dates and times, monetary values, and other locale-specific settings.

While LC_ALL is indeed a significant environment variable that can override other locale settings to provide a universal setting for all categories, it doesn't specifically define the character set itself. Instead, it serves as a way to set all locale variables to the same value in one command. If LANG is set, it will influence the character set used, as it specifies the language and localization settings that include character encoding.

CHARSET is not a standard environment variable in the same way as LANG or LC_ALL; it is often part of other variables, indicating that it may not be universally recognized across different Linux distributions. LC_TIME pertains specifically to the formatting of date and time, which doesn't encompass the character set.

Therefore, LANG is the primary environment variable used to define the character set on the Linux system, making it the correct choice in the context provided.