Join multiple mp4 files in Linux

The best way to do this currently is with the concat demuxer. First, create a file called inputs.txt formatted like so:

file '/path/to/input1.mp4'
file '/path/to/input2.mp4'
file '/path/to/input3.mp4'

Then, simply run this ffmpeg command:

ffmpeg -f concat -i inputs.txt -c copy output.mp4

Source: https://superuser.com/questions/521113/join-mp4-files-in-linux