Merge error and log files into 1 file

dump.sh

#!/bin/bash          
tail -n +1 file1.txt file2.txt file3.txt >> log.txt

#==> file1.txt <==
#<contents of file1.txt>
#==> file2.txt <==
#<contents of file2.txt>
#==> file3.txt <==
#<contents of file3.txt>