CompTIA Linux+ XK0-006 (V8) Practice Question

The correct answer uses the [[ ... ]] conditional construct with the =~ operator. In bash, [[ ... ]] is a keyword that provides extended features for tests. The =~ operator, when used within [[ ... ]], matches the string on the left against the extended regular expression on the right. The pattern ^app-[0-9]{4}-[0-9]{2}-[0-9]{2}\.log$ correctly matches a string that starts with app-, followed by four digits, a dash, two digits, a dash, two digits, a literal dot (\.), and ends with log.

• The option using == "app-*-*-*.log" is incorrect because == inside [[...]] performs pattern matching using globbing rules, not regular expressions, and the asterisks here would not correctly validate the digit-only format of the date components.
• The option using [ ... =~ ... ] is incorrect because the =~ operator is a feature specific to the [[ ... ]] construct in bash and is not defined for the POSIX [ command.
• The option using -eq is incorrect because -eq is a numerical comparison operator used to check if two integers are equal and will result in an error when used with non-integer strings.