#!/bin/bash

err_file="/tmp/getaudio_$$"

if [[ -z "$1" ]]; then
  printf 'Need a filename of a video\n' >&2
  exit 1
fi

input_file="$1"
if [[ ! -f "$input_file" ]]; then
  printf "Can't read %s\n" >&2
  exit 1
fi

base_path="$(dirname "$input_file" 2>"$err_file")"
err="$(<"$err_file")"

if [[ -n "$err" ]]; then
  printf '%s\n' "$err" >&2
  exit 1
fi

audio_ext="$(ffprobe "$input_file" 2>&1 | sed -nr 's/.*Audio: (...).*/\1/p')"

if [[ -n "$2" ]]; then
  if [[ "$2" == *.* ]]; then
    audio_out="$2"
  else
    audio_out="${2}.${audio_ext}"
  fi
else
  out_file="$(basename ${input_file%%.*})"
  audio_out="${base_path}/${out_file}.${audio_ext}"
fi

echo ffmpeg -i "$input_file" -vn -acodec copy "$audio_out"
ffmpeg -i "$input_file" -vn -acodec copy "$audio_out"