STEP 1: Create file with individual video files

echo file video1.mp4 > inputvideos.txt
echo file video2.mp4 >> inputvideos.txt

STEP 2: Combine them

ffmpeg -f concat -i inputvideos.txt -c copy MergedVideo.mp4

TIPS:

#!/bin/bash


OIFS="$IFS"
IFS=$'\n'

files="$(find "$1" -type f -name '*.mkv' -or -name '*.MOV' -or -name '*.avi' -or -name '*.mp4' -or -name '*.ogg' -or -name '*.mov' -or -name '*.flv')"

for f in $files; do
    # get path
    d="${f%/*}"
    # get filename
    b="$(basename "$f")"
    echo file $b >> inputvideos.txt
done
IFS="$OIFS"