Joining multiple video files is called concatenating, concat by short.
$ avconv -i concat:"VTS_01_1.VOB|VTS_01_2.VOB|VTS_01_3.VOB" -c copy new_file_name.mpgJoining multiple video files is called concatenating, concat by short.
$ avconv -i concat:"VTS_01_1.VOB|VTS_01_2.VOB|VTS_01_3.VOB" -c copy new_file_name.mpg