#!/bin/sh if [ "$#" -eq 0 ]; then set -- /dev/stdin fi for pathname do gawk -f awk_prac.awk "$pathname" done

if [ "$#" -eq 0 ]; then cat else printf '%s\n' "$@" fi |

if [ "$#" -ne 0 ] then printf '%s\n' "$1" else cat fi |

Do not pass arguments right into subshell, it's as unsafe as eval.

One good use for /dev/tty is if you're trying to call an editor in a pipeline (e.g., with xargs). Since the standard input of xargs is some list of files rather than your terminal, just doing, e.g., | xargs emacs will screw up your terminal. Instead you can use | xargs sh -c 'emacs "$@" </dev/tty' emacs to connect the editor to your terminal even though the input of xargs is coming from elsewhere.

When you have a pipeline, unbuffer must be applied to each element except the last (since that doesn't have its output redirected). Example: unbuffer p1 | unbuffer p2 | unbuffer p3 | p4