title: about PATH variable UNIX
body: <p>I see in examples of .profile file in UNIX systems, that after giving a value to the PATH variable e.g. <code>PATH=$PATH:.</code> and then it is exported <code>export PATH</code>.</p>
  
  <p>My question are 2:</p>
  
  <ol>
  <li>Why will happen if I don't export PATH after giving it a value?</li>
  <li><code>PATH=$PATH:.</code> means that the current directory is added to PATH variable. But is this done only 1 time? I mean will it just add my home directory, or every time I change the directory it will add it to PATH?</li>
  </ol>