title: Grep and returning only column of match
body: <p>if i want to search from a file with various number of columns like this:</p>
  
  <pre><code>ppl:apple    age:5    F    add:blabla    love:dog
  ppl:tom    M    add:blablaa    love:cat
  ppl:jay    age:3    M    love:apple
  ppl:jenny    acc:jen    age:8   F   add:blabla
  
  ...
  </code></pre>
  
  <p>the file is tab separated, and the output i want is:</p>
  
  <pre><code>age:5
  age:3
  age:8
  ...
  </code></pre>
  
  <p>using <code>grep age:</code> will return the entire row, while
  using <code>cut -f2</code> will return some unwanted column:</p>
  
  <pre><code>age:5
  M
  age:3
  acc:jen
  </code></pre>
  
  <p>and neither <code>cut -f2|grep age:</code> nor <code>grep age|cut -f2:</code> work  </p>
  
  <p>My data may range from 11-23 columns, 
  will there be any simpler way to handle it using grep sed or awk, 
  many thanks </p>