Question

Is there an easy way, when running a Ruby script, to get it to automatically install gems required for script?

For example, consider these require statements at the top of a ruby script:

require 'net/http'
require 'fileutils'
require 'archive/zip'

Now, I know (as a human and programmer) that for this script to run on a given PC with Ruby, the ‘gem install archive-zip’ command needs to be run first, before the script will work. But if this script needs to run on dozens of PCs, is there anything that can save me from having to ensure ALL the gem dependancies are installed first?

Furthermore, what if there are several gems required?

Answer 1

Not sure if this is exactly what you are after but when I have a server set up how I want I dump a list of my gems to somewhere safe…

gem list > my_gems.txt

If I need to rebuild the box or build another machine I use this script to install the gems…

bulk_gems.rb
#! /usr/local/bin/ruby

STDIN.readlines.each do |l|
 m = l.match /^(\S+) \((.*)\)/
 unless m.nil?
   gem_name, versions = m[1], m[2].split(',')
   versions.each do |v|
     system "gem install #{gem_name} --version #{v} --ignore-dependencies"
   end
 end
end

more my_gems.txt | bulk_gems.rb