How to call shell commands from Ruby

Question

How do I call shell commands from inside of a Ruby program? How do I then get output from these commands back into Ruby?

Answer 1

Given a command like attrib:

require 'open3'

a="attrib"
Open3.popen3(a) do |stdin, stdout, stderr|
  puts stdout.read
end

I've found that while this method isn't as memorable as

system("thecommand")

or

`thecommand`

in backticks, a good thing about this method compared to other methods is backticks don't seem to let me puts the command I run/store the command I want to run in a variable, and system("thecommand") doesn't seem to let me get the output whereas this method lets me do both of those things, and it lets me access stdin, stdout and stderr independently.

See "Executing commands in ruby" and Ruby's Open3 documentation.