title: Conditional Awk hashmap match lookup
body: <p>I have 2 tabular files. One file contains a mapping of 50 key values only called <strong>lookup_file.txt.</strong>
  The other file has the actual tabular data with 30 columns and millions of rows. <strong>data.txt</strong>
  I would like to replace the id column of the second file with the values from the <strong>lookup_file.txt.</strong>.</p>
  
  <p>How can I do this? I would prefer using awk in bash script..
  Also, Is there a hashmap data-structure i can use in bash for storing the 50 key/values rather than another file? </p>