title: Matching a precise number of characters in Regex
body: <p>Matching a precise number of characters {min,max}</p>
  
  <p>File name (input_file) contains text as like below:</p>
  
  <p>The Unix operating system was pioneered by Ken
  Thompson and Dennis Ritchie at Bell Laboratories
  in the late 1960s.</p>
  
  <pre><code> grep '[A-Za-z]\{4,7\}' input_file
  </code></pre>
  
  <p><strong>Output:</strong> grep command output, matched characters are marked in Bold letters for the references.</p>
  
  <p>The <strong>Unix</strong> <strong>operati</strong>ng <strong>system</strong> was <strong>pioneer</strong>ed by Ken
  <strong>Thompso</strong>n and <strong>Dennis Ritchie</strong> at <strong>Bell</strong> <strong>Laboratories</strong>
  in the <strong>late</strong> 1960s.</p>
  
  <p>After the execution of grep command, </p>
  
  <p>first  word Unix:</p>
  
  <p>Total number of word 4, so character Matching <strong>Unix</strong> with character long 4/4.</p>
  
  <p>second word operating:</p>
  
  <p>Total number of word 9, so character matching <strong>operati</strong>ng with 
  character long 7/9.</p>
  
  <p>Third word system:</p>
  
  <p>Total number of word 6, so character matching <strong>system</strong> character long 6/6.</p>
  
  <p>Fourth word <strong>pioneer</strong>ed</p>
  
  <p>Total number of word 9, so character matching <strong>pioneer</strong>ed character long 7/9.</p>
  
  <p>Fifth word <strong>Thompso</strong>n</p>
  
  <p>Total number of word 8, so character matching<strong>Thompso</strong> character long 7/8.</p>
  
  <p>Sixth word <strong>Dennis</strong></p>
  
  <p>Total number of word 6, so character matching <strong>Dennis</strong> character long 6/6. </p>
  
  <p>Here my question is ? Word six having Dennis total number of character 6 but i mentioned {4,7} length long how it will matching entire word, i am not understating here.</p>
  
  <p>Could you please some help me on this?</p>