CompTIA Linux+ XK0-006 (V8) Practice Question

The correct answer uses the [[...]] conditional construct with the =~ operator. In Bash, the =~ operator, when used within double square brackets [[...]], performs an extended regular expression match. The regular expression ^[0-9]+\.[0-9]+\.[0-9]+$ correctly defines the 'major.minor.patch' format by anchoring the match to the start (^) and end ($) of the string and looking for one or more digits ([0-9]+) separated by literal periods (\.).

The expression [ $VERSION =~ ... ] is incorrect because the single bracket [ construct (the test command) does not support the =~ regex matching operator.

The expression [[ $VERSION == ... ]] is incorrect because the == operator inside double brackets performs glob-style pattern matching, not regular expression matching.

The expression (test $VERSION -eq ...) is incorrect because test is the same as the single bracket [ construct and does not support =~. Additionally, -eq is a numerical comparison operator, not a string or regex operator.