Prepend one file to another in bash

prepend.sh

# this will find all folders with a file named versions.tf
# and prepend its contents to the file main.tf in the same directory
for p in $(find -name "versions.tf"); do
  main=$(echo $p | sed 's/versions/main/' );
  echo -e "$(cat $p)\n\n$(cat $main)" > $main;
done