For some time, "Learning the Korn Shell" was the only source I had for k-shell programming. That was a bad idea. O'Reilly books are usually first-rate, but I guess they can't knock every pitch out of the park. I cannot recommend this book either as an introductory tutorial or as a reference. The first problem is that topics seem to be jumbled together, so that things are hard to find and to follow. Secondly, many subjects are either not covered at all, or are given the proverbial lick and a prayer. Even worse, the indexing is terrible. I find too many cases in which important things (like dot scripts, for instance) are simply not in the index, if they are covered at all in the text. Fortunately, there are alternatives to this book which I find much more satisfactory. By far the best is "The Korn Shell User and Programming Manual", by Anatole Olczak, an Addison-Wesley publication. It's pricey (about $50), but it's well-organized, complete, and very competently indexed.