Learning Chef FileEdit (based on https://learn.chef.io/learn-the-basics/ubuntu/configure-a-resource/)

hello.rb

## Simple extension of the Chef tutorial for appending line(s) to the end of a cookbook
## Alternative to copying an entire cookbook just to add one line to a config file.
## (Apparently, partials are an alternative in Chef 11?
## http://stackoverflow.com/a/19167106/7507

file 'motd' do
  content "hello chef\n"
end

ruby_block "ensure sig to end of file" do
  block do
    fe = Chef::Util::FileEdit.new("motd")
    fe.insert_line_if_no_match(/@noahlz/, "@noahlz was here")
    fe.write_file
  end
end

output.txt

[nzucker: motd]$ echo "hello chef" > motd
[nzucker: motd]$ cat motd
hello chef
[nzucker: motd]$ sudo chef-apply hello.rb
Recipe: (chef-apply cookbook)::(chef-apply recipe)
  * file[motd] action create (up to date)
  * ruby_block[ensure sig to end of file] action run
    - execute the ruby block ensure sig to end of file

[nzucker: motd]$ cat motd
hello chef
@noahlz was here