title: How to better merge .gz files?
body: <p>I want to merge two files ending with .gz. I have tried two ways among others. For the first way, I directly concatenated the files using cat; for the other way, I first decompressed each file through gunzip, and then concatenated the decompressed files before compressing again using gzip. Interestingly, I found that the resulting files vary in size. Could anyone answer my puzzle here?</p>
  <p>Thank you in advance!</p>