#! /bin/bash
cmd="$1"
shift
f="$*"
if [[ -z "$f" && "$cmd" == *\ * ]]; then f="${cmd#* }"; cmd="${cmd%% *}"; fi
if [[ -z "$f" ]]; then echo try: \`f command filename; elif [[ -e "$f" ]]; then "$cmd" "$(< "$f")"; else echo no such file: "$f"; fi