CompTIA Linux+ XK0-006 (V8) Practice Question

The expression [ "$proc_count" -eq 0 ] invokes the POSIX test (or [ ) utility and uses the -eq arithmetic operator, whose specification states "n1 -eq n2 - True if the integers n1 and n2 are algebraically equal." This returns exit status 0 only when the variable's value is the integer 0.

[[ "$proc_count" == 0 ]] performs a string comparison, so values like "00" would also match and it is not POSIX-portable. [ $proc_count -ne 0 ] is the logical opposite of what is needed, succeeding when at least one process is running. (( proc_count = 0 )) assigns 0 to the variable; the assignment's result is 0, yielding a false exit status, so the branch would never run.

Therefore, only the first test fulfills the requirement accurately and portably.