Bash Script To Extract Subtitles From MKV file

sub-extractor

#!/usr/bin/bash
nano sub-extractor.sh   
 ###paste the following  
filename="$1"
if [[ $filename ]]
then 
 m=$(mkvinfo $filename|grep 'No EBML head found');
 if [[ $m ]];
  then echo "This is not a valid mkv file";
  else  
    echo "proceeding...";
    mm=$(mkvinfo $filename|grep -i -A 2 -B 2 subtitle);
    if [[ $mm ]];
     then
      echo "subtitles found, proceeding...";
      mmm=$(echo $mm|grep -o 'mkvextract: [0-9]*'|grep -o '[0-9]*')
      arry1=$(echo $mmm|tr " " "\n ");
      for m in $arry1
       do mkvextract tracks $filename $mmm:${filename:0:-4}"_"$mmm; 
      done
    else 
     echo "no subs";
 fi;
 
   fi;
else
 echo "no file name given";
fi;