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Book Review: Linux Shell Scripting Cookbook 173

vellorean writes "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." Read below for the rest of vellorean's review.
Linux Shell Scripting Cookbook
author Sarath Lakshman
pages 360
publisher Packt Publishing
rating 9
reviewer Kumar Appaiah
ISBN 1849513767
summary A book for beginners and intermediates, which introduces shell scripting and proceeds to provide several practical real-world recipes of useful shell scripts
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.

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 he 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.

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.

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.

You can purchase Linux Shell Scripting Cookbook from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.


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Book Review: Linux Shell Scripting Cookbook

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  • by mugnyte ( 203225 ) on Friday April 15, 2011 @02:17PM (#35831924) Journal

    wow. how many ways can i answer that?

      - there is no one true way
      - people learn a skill and want to continue using it
      - concise syntax / small footprint / fast load times
      - high confidence shell scripts will run on unknown systems
      - can be layered on years of useful scripts
      - distrust of your options for doing work

  • by beatle42 ( 643102 ) on Friday April 15, 2011 @02:21PM (#35831972)
    I find it useful to do shell scripting when I've been doing something by hand, and want to automate it. It's pretty easy to just echo the command I've been doing into a file and touch it up from there. Then I can take advantage of the organic growth of the command as it usually happens, and can also use it to run that same command on lots of systems if needed.
  • by Anonymous Coward on Friday April 15, 2011 @02:22PM (#35831984)

    Sysadmins who can't work in plain shell scripts are dangerous. What will you do if you lose your /usr filesystem ? Be stuck with no automation tools at all as you fix by hand ? Shell scripts have little or not dependencies, and can function where other languages aren't available.
    More-over they are ubiquitious. Perl, python and ruby are common in Linux, but what will you do if you're on a different Unix altogether ? A sysadmin who can use shells efficiently can easily transfer his skills to solaris, hp-ux or several others (I did just that, and now I'm paid quite a lot more than a Linux sysadmin earns as a Unix sysadmin because the skillset is rarer). Of course there are other skills you'll need to learn (package management for example is vastly different between various unixes and most are frankly primitive if you are used to Linux) but the core Unix fundamentals remain the same, and if you don't know powerful and flexible shell scripting, in my book, you're no sysadmin at all.

  • by prgrmr ( 568806 ) on Friday April 15, 2011 @02:36PM (#35832160) Journal
    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

    Seriously? So you write your application's /etc/init.d scripts in something other than bash (or csh if on solaris, or ksh if on aix)? Granted not everyone would want, let alone try, to write 500+ line bash scripts like I occasionally do; but, there are a ridiculous number of 100+ line perl scripts that could have been done in bash or ksh in fewer lines, and with more clarity, and without the overheard of loading dozens of perl modules due to interdependencies among them.
  • by mmell ( 832646 ) <mike.mell@gmail.com> on Friday April 15, 2011 @02:40PM (#35832196)
    There's a reason we use /bin/sh (Bourne) to write scripts, and it's the same reason we use vi to edit them - mainly it's available on ALL UNIX systems. Despite widespread adoption, bash is not universally available - sorta like EMACS.

    If I stick it in root's cron on, say, an AIX system and it pukes I'm not interested in rewriting somebody's bash script to handle running under sh, csh or ksh. I want it written by its original author in sh. And I don't want to hear about a shebang line (#! /bin/bash) - if I haven't installed bash, it'll still puke.

  • by Zenin ( 266666 ) on Friday April 15, 2011 @03:04PM (#35832496) Homepage

    In particular Bourne shell makes gluing other programs together far easier, cleaner, and more reliably then can be done with any of the languages you list...and I say that even given that I'm extremely fluent in at least two of them.

    Correctly and reliably handling even a simple "foo | bar | baz" construct in the languages you list can be done, but you're talking about an LOT of non-trivial systems level programming to do it, effectively "coding C inside perl/python/ruby". No, really. Sure, it's very easy to do it wrong and fragile (just call system(), what's so hard right?), but if you actually want to handle it as correctly and reliably as Bourne does out of the box...it's going to take a hell of a lot more code and detailed systems programming knowledge then even most "Sr" Unix sysadmins tend to have. Almost without fail ever attempted I've ever seen in the industry gets it wrong...typically very, very wrong.

    Bourne is built to run other programs, to manage the interactions between them, programming logic being the exceptional use. All of the languages you list are built to be self-contained, programming logic being the primary task and communicating with external programs a very secondary use.

    Now of course...if your script/program is self-contained and not just wrapping a bunch of exec()s of other programs, then sure Bourne shell is one of the least favorable options.

    There's also nothing saying you can't freely mix and match. Most anyone worth their salt does so all the time. To do otherwise would be like saying a web coder could only work in HTML or only work in JavaScript or only work in PHP. We're talking about complimentary languages here, with some overlap.

    Use the right tool for the job.

  • by fnj ( 64210 ) on Friday April 15, 2011 @05:11PM (#35834194)

    OK, how much RAM does your router have? Your cable modem? A small NAS device? Your concept of embedded devices may be only a small fraction of what's out there.

Your code should be more efficient!