#!/bin/bash

rm mylist.txt
rm merged.mp4
touch merged.mp4
rm merged.mp4
#listfiles=`ls -cr *.mp4`
listfiles=`ls *.mp4 *.m4v *.mkv`

for f in $listfiles; do echo "file '$f' " >> mylist.txt; done
ffmpeg -safe 0 -f concat -i mylist.txt -c copy -y merged.mp4