#!/bin/sh

# Check if any arguments are given
[ "$#" -eq 0 ] && echo "No input file given" && exit 1

# Check if input file is wav
file "$1" | grep -q 'WAV' || { echo "Wrong input file given"; exit 1; }

# Use input file name as output file name
[ "$#" -eq 1 ] && OUTPUT="$(echo $1 | sed 's/\.wav$/.mp3/')"

# Use second argument as output file name
[ "$#" -eq 2 ] && OUTPUT="$2"

ffmpeg -i $1 -vn -ar 44100 -ac 2 -b:a 192k -f mp3 $OUTPUT