#!/bin/rc switch($#*) { case 0 awk '{printf("%-5d\t%s\n",NR,$0)}' case 1 awk '{printf("%-5d\t%s\n",NR,$0)}' < $1 case * echo 'usage: catn file' >[1=2] echo ' catn < file' >[1=2] echo ' cat file | catn' >[1=2] }