If you're using bash, things can be a little simpler. Here's the general command I use for converting video files. (You can replace the ffmpeg line with your preferred conversion technique)

for i in *.vob; do

ffmpeg -i $i -acodec mp3 -ab 128k -vcodec mpeg4 -qscale 4 ${i%%.vob}.avi

done

$i becomes each vob filename and the sequence ${i%%.vob} rips off the .vob extension.