title: character class range in awk version 3.1.7
body: <p>Unlike <code>grep</code> I am not able to define the size/range of digit character class in `awk. Any clue to right direction is appreciated. </p>
  
  <pre><code>cat input
  1abc
  12abc
  123abc
  1234abc
  12345abc
  </code></pre>
  
  <p>In <code>grep</code> I can define the size/length  of digit char class</p>
  
  <pre><code>grep -P '^\d{3,4}' input #or grep -P '^[[:digit:]]{3,4}' input
  123abc
  1234abc
  12345abc
  grep -P '^\d{4,}' input  #or grep -P '^[[:digit:]]{4,}' input 
  1234abc
  12345abc
  </code></pre>
  
  <p>Now I want to do this with awk,but the same regex is not working. </p>
  
  <p>for example Following command does not give any output. </p>
  
  <pre><code>awk '/^[[:digit:]]{3,4}/' input 
  awk '/^([[:digit:]]){3,4}/' input
  </code></pre>
  
  <p>I was expecting above command to print </p>
  
  <pre><code>123abc
  1234abc
  12345abc
  </code></pre>
  
  <p><strong>Note 1</strong>: Currently I am using to define range but it is not sweet for big range. </p>
  
  <pre><code>awk '/^[0-9][0-9]?[0-9]?/' input
  </code></pre>
  
  <p><strong>Note 2:</strong></p>
  
  <pre><code>awk --version |head -1
  GNU Awk 3.1.7
  </code></pre>