This is a 1000+ page tutorial on shell scripting under the Linux (or other UNIX-like) operating system. It is free to download and use, and freely distributable. I have placed it in the Public Domain, so it is not copyrighted, and there are no restrictions on its use or distribution.
This is the 2014 Final Update version, and it is downloadable in epub and pdf formats from
the archive.org site.
https://archive.org/details/abs-guide
Note that the book is free to download, but I will happily accept contributions.