VLC player merge command

You can try these commands to concatenate mp4 files using VLC player
 
1) vlc 01.mp4 02.mp4 --sout "#gather:std{access=file,dst=03.mp4}" --sout-keep

2) vlc 1.mp4 2.mp4 3.mp4 --sout "#gather:std{access=file,dst=out.mp4}" --sout-keep