#!/bin/sh -e

# Runs a stream command on a file

# Usage: self file command

file="$1"

shift

temp="$(tempfile)"

onExit () { rm -f "$temp"; }

trap onExit EXIT

"$@" <"$file" >"$temp" # exits on error so file not updated

diff "$file" "$temp" >/dev/null && exit # don't update file if no change

mv "$temp" "$file"