title: Replace whitespace with a comma in a text file in Linux
body: <p>I need to edit a few text files (an output from <code>sar</code>) and convert them into CSV files.</p>
  
  <p>I need to change every whitespace (maybe it's a tab between the numbers in the output) using sed or awk functions (an easy shell script in Linux).</p>
  
  <p>Can anyone help me? Every command I used didn't change the file at all; I tried <code>gsub</code>.</p>