title: Large text file and characters Limitation problems in a line
body: <p>I have a text file that each line of it ,is a record of data with a specific structure.
  I want to read it Line by Line, in a specific Line for example in Line 1000 Change a data Like:</p>
  
  <pre><code> sara , 1991 , Zakizadeh , Student , Tehran
   Eli , 2005 , Lord , teacher , London
   Elias , 1875 , Lion , farmer , Berlin
  </code></pre>
  
  <p>Change to:</p>
  
  <pre><code> sara , 1991 , Zakizadeh , Student , Tehran
   Eli , 2005 , Lord , teacher , London
   Elias , 1875 , Star, farmer , Berlin  ****
  </code></pre>
  
  <p>I can find the number of line and and can change the data and update the same line, but there are some problems:</p>
  
  <ul>
  <li>maybe the amount of characters in a line after update be more than a line and it be continued in another line! </li>
  <li>if I want to prevent top problem , I can to put limitation for each data for example Name : 20 Char , Birth date: 4 char ,.... but if its data be less than this amount it can make Redundancy in such a large file about more than 6000 lines.</li>
  </ul>
  
  <p>What is your solution?</p>