CompTIA Linux+ XK0-006 (V8) Practice Question

The function increment declares its own local variable named counter. That local variable shadows the global counter for the life of the function call, is incremented to 1, and then is discarded when the function returns. Because the global counter was never modified, the echo statement that follows the function call outputs the original value 0. The script therefore prints 0. The other answers are wrong because:

• 1 would appear only if the global counter were modified, which it is not.
• A blank line would occur only if counter were unset or empty, which is not the case.
• An unbound-variable error would occur only if the shell were running with 'set -u' (or 'set -o nounset') and counter were undefined, which again is not true here.