Multiple choice technology programming languages

$touch {a}_{b,c} What is the output

  1. creates a_b,c file

  2. syntax error

  3. changes the timestamps of a_bc file

  4. creates a_b and a_c files

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Shell brace expansion evaluates {a}_{b,c} into the arguments a_b and a_c. Consequently, running touch on this pattern creates or updates the timestamps of both a_b and a_c files.