Humble Bundle - O'Reilly UNIX Books ~$1.35AUD-$21AUD

Humble Bundle has a range of *Nix related O'Reilly titles raising money for Code For America.

Yes, some are very old versions (eg. OS X Unix is Tiger era) but most of the UNIX tools outlined matured well before this, and the books are worth in the order of $500 US at full retail.

There are PDF, ePub and Mobi download options.

Pay $1 US or more:

• Unix in a Nutshell, 4th Edition
• sed & awk, 2nd Edition
• lex and yacc, 2nd Edition
• Learning the bash Shell, 3rd Edition
• Linux Pocket Guide, 3rd Edition

Pay $8 US or more:

• bash Cookbook
• Classic Shell Scripting
• Learning GNU Emacs, 3rd Edition
• Unix Power Tools
• Learning the vi and Vim Editors, 7th Edition
• Bash Pocket Reference, 2nd Edition
• Learning Unix for OS X, 2nd Edition

Pay $15 US or more:

• Essential System Administration, 3rd Edition
• TCP/IP Network Administration, 3rd Edition
• DNS and BIND, 5th Edition
• Network Troubleshooting Tools