Spotted on Reddit, guessing this offer may be rather to quite limited time:: https://www.reddit.com/r/commandline/comments/rnlaxi/merry_christmas_i_am_gi...
Merry Christmas! I am giving away my ebook Command Line: A Modern Introduction for free. Grab your copy as a gift :)
1. Go to https://stribny.gumroad.com/l/moderncommandline
2. Enter "christmas" as the discount code
3. Enjoy your Christmas gift:)