IMHO, the best resource to learn about both Unix shell usage at the command-line prompt, and shell programming in .sh script files, is still the book "The Unix

IMHO, the best resource to learn about both Unix shell usage at the command-line prompt, and shell programming in .sh script files, is still the book "The Unix Programming Environment" by Kernighan and Pike, except for shell gotchas and subtleties which were discovered later. Of course, they still would not have covered all possible issues known even at that time, because that was not the focus of the book, which was to be a Unix tutorial, not just on shell, but many other commands, general Unix usage, and the environment too (hence the title of the book). But they did cover and warn about some issues, including giving solutions.