title: Join two files using awk
body: <p>I have two files like shown below which are tab-delimited:</p>
  
  <p>file A</p>
  
  <pre><code>chr1   123 aa b c d
  chr1   234 a  b c d
  chr1   345 aa b c d
  chr1   456 a  b c d
  ....
  </code></pre>
  
  <p>file B</p>
  
  <pre><code>xxxx  abcd    chr1   123    aa    c    d    e
  yyyy  defg    chr1   345    aa    e    f    g
  ...
  </code></pre>
  
  <p>I want to join the two files based on 3 columns with "chr1", "123" and "aa"  and add first two columns from file B to file A, such that output looks as shown below:
  output:</p>
  
  <pre><code>chr1   123    aa    b    c    d    xxxx    abcd
  chr1   234    a     b    c    d
  chr1   345    aa    b    c    d    yyyy    defg
  chr1   456    a    b    c    d
  </code></pre>
  
  <p>Could anyone help to do this in awk. If possible using awk oneliners?</p>