system.rb

#0> non-block call

Thread.new do
  blahbla...
end

#1> 4 simple ways to call shell or cmd

`ps aux`

system "ps aux"

exec "ps aux"

%x{ ps aux }

%x[git init]
 
matrix.each do |day|
  if day == "o"
    %x[git commit --allow-empty --author="#{author} <#{email}>" --date="#{date.to_time}" -m"#{date.to_time} - by: #{author}"]
  end
  date = date.next
end

#2> open3 popen & :pid

require 'open3'

Open3.popen2 "ps aux" do |i, o, t|
  :pid = t.pid
end

#3> open3 capture & :pid

require 'open3'

o,s = Open3.capture2("ps aux")
:pid = s.pid

#4 Process spawn

:pid = Process.spawn "ps aux"