title: How to modify specific columns using sed
body: <p>How to modify a specific folumn by sed, especially apply add numeric numbers to that column data.</p>
  
  <p>I have a csv file looks like this:</p>
  
  <pre><code>c1,c2,123,c4
  c1,c2,345,c4
  </code></pre>
  
  <p>is it possible to add 400 to column 3 of each row?
  and makes the result look like the below:</p>
  
  <pre><code>c1,c2,523,c4
  c1,c2,745,c4
  </code></pre>
  
  <p>I tried by myself using </p>
  
  <pre><code>"sed -n 's/[0-9]\{3\}/&amp;+400/ p' test.csv "
  </code></pre>
  
  <p>and the result is </p>
  
  <pre><code>c1,c2,123+400,c4
  c1,c2,345+400,c4
  </code></pre>