"The New KORN Shell" by Bolsky and Korn. (Note that one of the authors is David Korn) My dogeared copy is well used but it is not a tutorial, it is a reference text. Also useful is that it documents the various revisions of the Korn shell. It is also a good reference for HP's POSIX shell since POSIX shells are very similar (ksh, bash, etc).
But there is a big jump from the commands to the technique. While a good Korn shell book will show you a few examples on using certain commands and variables, technique is what makes for stable and reliable shell programs. I always start my shell programs with the courtesy loader directive (always a good idea for every interpreted language such as perl or ksh or csh, etc), followed by set -u (to avoid big errors later), then if the program will need tempfiles, I created a unique temp directory (not a tempfile). That way, I can store all my temp files in one spot and use the trap command to remove everything if the program is aborted or terminates normally. I will code variables as ALL CAPS so they stand out, functions are name with LeadingCaps, and I tenmd to code about 20-30% comments, mostly because I forget why I did something a certain way.
Other techniques are found simply by reading shell scripts and figuring out what is happening. Look at the Shelldorado website
http://www.shelldorado.com/ which gives a lot of techniques for good scripting. Another resource for HP-UX scripts (that do useful things) is: ftp://contrib:9unsupp8@hprc.external.hp.com/sysadmin/coolscripts/
Bill Hassell, sysadmin
