Question

I have a directory full of ruby scripts for common tasks, and I’ve started to accumulate a set of common variables and methods that I find myself defining in each new script. The next step in improving this would seem to be creating a file (say, commonstuff.rb) and “require”ing that file from the other scripts so that the common variables and methods are all available everywhere and defined only once.

A simple attempt that didn’t work:

commonstuff.rb

username=ENV['USER']
home_dir_path=ENV['HOME']

def print_and_execute(command, &block)
  puts command

  process_io = IO.popen(command + "2>&1")

  while(line=process_io.gets)
    if (block != nil)
      yield line
    else
      puts line
      STDOUT.flush
    end
  end
end

script1.rb

#!/usr/bin/env ruby
require File.dirname(__FILE__) + '/common_stuff'

puts home_dir_path         # Fail
print_and_execute "date"   # Fail

I’ve used ruby libraries and frameworks, but I don’t have any of that available in my current environment. I just have straight ruby, and I’m a little rusty on some of the basic idioms that would work well here, or that would look right to a ruby expert.

Any help appreciated!

Answer 1

Wrap your methods and variables in a module, e.g.

module CommonStuff
    USERNAME=ENV['USER']
    HOME_DIR_PATH=ENV['HOME']

    def print_and_execute(command, &block)
        ...
    end
end

Then script1.rb might be like:

#!/usr/bin/env ruby
require File.dirname(__FILE__) + '/commonstuff.rb'
include CommonStuff

puts HOME_DIR_PATH         # Win
print_and_execute "date"   # Win

Or, if you don’t want to include the module in your namespace:

#!/usr/bin/env ruby
require File.dirname(__FILE__) + '/commonstuff.rb'

puts CommonStuff::HOME_DIR_PATH         # Win
CommonStuff.print_and_execute "date"   # Win

See also Modules and the Programming Ruby page on modules.