title: last command in linux shows `:0` in 3rd column, what does it mean?
body: <p>I want to write a shell script sort out the data that <code>last</code> command shows.
  I got this in my server.</p>
  
  <pre><code> root    pts/0        10.168.136.175     Wed Sep 14 14:24 - 14:54   (00:29)        
   root    :0                              Mon Sep 12 10:34 - 11:00   (00:25)       
   reboot  system boot  2.6.18-308.el5PA   Sun Sep 11 11:31           (86+03:05)
  </code></pre>
  
  <p>I did some search, there are some saying <code>:0.0</code> in the 3rd column means login locally, second column means what kind of terminal been use, like <code>pts</code> and <code>tty</code>.</p>
  
  <p>But what does the <code>:0</code> in line 2 second column in my log?<BR>
  I am using redhat 6.5.</p>