Grep expressions are not a turing-complete language, so I guess that won't count. You could claim that you solved the task using a shell script (that invoked t

Grep expressions are not a turing-complete language, so I guess that won't count. You could claim that you solved the task using a shell script (that invoked the grep "function") but if you programmed in shell, the shortest solution AFAICS is #!/bin/sh cat