#!/bin/bash

# Takes input from standard input and overwrites output argument file only if
# they differ

input="$(cat)"
output="$1"

new="$(sha256sum <<<"$input" | cut -d " " -f 1)"
old="$(sha256sum "$output" 2>/dev/null | cut -d " " -f 1)"

if [ "$new" != "$old" ]; then
    echo -n "$input" > "$output"
fi