Lately, I’ve been thinking about how to automate some commandline stuff. I knew about expect, so I started to dig into similar solutions for ruby. Turns out, there’s expect, but … it looks kind of complicated. And that’s how the search for gems with a nicer API started. I fire up github, and I write ruby expect in the searchbox. As expected, a ton of results, but some of them look promising. Until I see that there’ve been no commits in quite some time.
So, I order them by Recently Updated. And I stumble upon greenletters.
Seeing that it’s from Avdi Grimm, it kind of instantly gets a lot of credibility from me.
I read the introductory blog post, and I’m hooked.
So, I’ve decided to write a simple script, to automate running heroku run bash, because why not, right?
The first try failed really fast
home/geo/.rvm/gems/ruby-2.2.1@russh/gems/greenletters-0.3.0/lib/greenletters.rb:648:in `process_interruption': Interrupted (timeout) while waiting for output matching /~ $/. (Greenletters
::SystemError)Turns out, greenletters seems to have a pretty small timeout by default. After a bit of browsing around in the issues section, I stumble upon the :timeout option, which looks to be exactly what I need. After that, things just started to fall into place, so without further ado, I present to you the most useful script, which runs ls -l and cats the Gemfile:
require "bundler"
Bundler.require(:default)
adv = Greenletters::Process.new("heroku run bash -a myherokuapp", :timeout => 100, :transcript => $stdout)
adv.start!
adv.wait_for(:output, /run.\d+.*?\$/m)
adv << "ls -l\n"
adv.wait_for(:output, /\$/)
adv << "cat Gemfile\n"
adv.wait_for(:output, /\$/)Low and behold, it works. The run pattern is in that way, because when heroku runs a command, it’s output has the following format:
Running `bash` attached to terminal... up, run.5710Also, the heroku shell command prompt looks like this ~ $. Hopefully, it makes sense why I used those regexes now.
I can see plenty of uses for such a gem, and it’s API is pretty nice to work with. Hopefully you can put it to great use. I’m interested to see what you’ll come up with :)