CompTIA Linux+ XK0-006 (V8) Practice Question

The correct answer uses the special variable $# and the numerical comparison operator -ne. The $# variable holds the count of positional parameters passed to the script. The -ne operator is used within a test ([ ]) expression to check if two numbers are not equal. Therefore, the expression [ $# -ne 1 ] will evaluate to true if the number of arguments is anything other than one.

• [ $@ -ne 1 ] is incorrect because $@ expands to the list of all positional parameters, not the count of them. It is unsuitable for a numerical comparison.
• [ $# != 1 ] is incorrect because != is the operator for string comparison, not numerical comparison. While some shells might handle this, -ne is the standard and correct operator for numerical tests.
• [ -z "$1" ] is incorrect because it tests if the first positional parameter ($1) is an empty string. This does not correctly check if the number of arguments is exactly one; for example, it would fail if the script was called with two arguments.