I have been reading Linux Shell Scripting Cookbook by Sarath Lakshman, published by Packt, for a while. While most people I know learn shell scripts themselves, I was looking to refresh my concepts a little as well as have a reference lying around on the table for fast access. Since I was asked to review it for someone else, I thought I might as well post the review here.
First of all, let me remark by saying that shell scripting is something learned more on a need basis than as a tool to solve the main problem. People would seldom write shell scripts as standalone programs (exceptions exist). However, what makes shell scripting invaluable to know is the fact that knowing some tricks can save several minutes, or hours, of work by automating and simplifying certain tasks, generally (but not restricted to) file management and data processing. Linux Shell Scripting Cookbook does go quite far in pursuing this goal, and is appropriate for both beginners who are looking to gain dexterity in shell scripting, as well as intermediate users who wish to polish their skills. The book also can double up as a quick reference, though I would argue that the "Advanced Bash Scripting Guide" would suit that more.
At the outset, the author clarifies that the focus will be on Bash. This, people may or may not like, but the fact that bash has become ubiquitous in terms of the available shells on Unix-like systems today, starting out with bash is not a bad thing to do. Besides, learning other shell scripting languages while knowing bash isn't too hard, since the paradigm remains the same.
Let's go through the books from the aspects I found most relevant.
The book is organized into chapters based more on utility than scripting concepts themselves, although the language aspects are brought onto the reader gradually. For instance, the examples in the first chapter focus more on the basic data elements (variables, arrays, functions etc.) as well as operators (for numbers, files etc.), and all the examples demonstrate simple usage of these concepts, and he further chapters build upon these in a gradual manner.
At the same time, if the reader has some familiarity with shell scripting and needs to only refresh or learn a certain concept, he/she needs to just read the relevant chapter. It is not too difficult to grasp the examples of the later chapters, provided some basic shell knowledge is assumed.
Content and Presentation
A positive trait in the presentation of this book is that it is all based on practical everyday examples which, with minor adaptation, can be used by many for their own daily tasks. For instance, there are several examples which describe searching for and processing files, which, I'd imagine, many users would want to do on a regular basis. Thus, providing realistic examples allows the book to double its utility. The language and approach used is simple and conversational, and the presentation is very clear, with each idea being described as a problem statement followed by a "How to do it" section with the actual code, and ending with a discussion of the nitty-gritties of the code. It is easy to go for a quick scan for those in a hurry, while those who with to read in more detail will not be disappointed either.
The book also covers a wide array of applications. For instance, there are examples on automating fetching web pages and processing them, demonstrations of parsing and simplifying and even some queries around databases wrapped around in shell. It also spans to utilities and tasks connected to statistics, backups, compression, version control and many more.
Breadth and Depth
The book goes into a fair amount of detail in terms of describing the shell scripting concept under consideration. The examples used go into a fair amount of detail in order to describe to the user all the aspects involved in the method or command being used. The concepts described are fairly complete, and would be sufficient for the reader to use immediately or with just a little bit of fine tuning. In terms of breadth, the book covers most of the features of shell scripting while also describing the various facilities the shell provides access to in a Unix-like environment. Thus, the book does not disappoint in this front either.
In summary, probably the only thing I'd have liked to see more of is some emphasis on how to write more efficient shell scripts. Granted, most of the shell scripts described in the book are very simple and succinct, but a some words on how loops can be made better, or how to spot situations where pipes are not needed to solve a problem etc. might have been a nice addition. Some explanation of differences with dash, tcsh, zsh etc. might also have been nice, since a lot of users have different default shells. But all this isn't going to prevent me from giving this book a high rating, since it delivers quite well on the promises it makes at the beginning.
This is definitely a good book to have near your desk, and kudos to the author for having taken the effort to put it together. I would highly recommend it to the beginner and occasional shell user for a thorough read, and to an intermediate to have on his/her desk for borrowing the cool scripting ideas and applications the author has written in this book.