title: Why doesn't my vim know my alias?
body: <p>I have used "alias ruby=ruby1.9.1", so I can execute my ruby with this:</p>
  
  <blockquote>
    <p>ruby 123.rb</p>
  </blockquote>
  
  <p>or</p>
  
  <blockquote>
    <p>ruby1.9.1 123.rb</p>
  </blockquote>
  
  <p>But in my vim, I use :!ruby and get
  /bin/bash: ruby: command not found.</p>
  
  <p>I must use :!ruby1.9.1</p>
  
  <p>How does alias work? Why vim doesn't know it?</p>