title: Regex Space character in Sed
body: <p>I've tried almost everything (I guess) but nothing worked. 
  (Operating System: Ubuntu 12.04)</p>
  
  <p>Expressions to be matched (removed from text files):</p>
  
  <pre><code>a c 4
  a k 23
  o s 1
  </code></pre>
  
  <p>What I tried: </p>
  
  <pre><code>'s/[[a-z][:space:][a-z][:space:][0-9]]\{1,\}//gi'
  's/.\s.\s[0-9]+//g'
  's/[:alpha:][:space:][:alpha:][:space:][:digit:]+'
  </code></pre>