Audio file extractor

audio_file_extractor.sh

#!/bin/sh

if [ $# != 1 ]
then
    echo 'syntax)' `basename $0` '<movie>'
    exit
fi

target=$1
base=`echo $target | sed -e 's@\.[a-z0-9]*$@@g'`
fmt=`ffprobe -i "$target" 2>&1| grep Audio: | sed -e 's@.*Audio: \([a-z0-9]*\) .*@\1@g'`

ffmpeg -i "$target" -map 0:1 -codec copy "$target.$fmt"
cname="$target.$fmt"

if [ "$fmt" == "aac" ]
then
    MP4Box -add "$cname" "$target.m4a"
    rm "$cname"
    cname="$target.m4a"
    fmt="m4a"
fi

mv "$cname" "$base.$fmt"