LINUX & UNIX Shell Programming
Author: David Tansley
Price: $44.95 US
Reviewer: Marjorie Richardson
When beginning to read LINUX & UNIX Shell Programming, I was a bit confused to find I was reading about shell basics and not programming. My conclusion was, Mr. Tansley is writing for the true beginner to UNIX and so is first providing background and command information that will be needed when the user actually begins writing scripts. He is covering the basic or Bourne shell, which is common to all UNIX flavors including Linux, so scripts will be portable. More than once, he emphasizes the fact that his scripts are not the most efficient design, but are easy to understand and reuse. The back of the book states all scripts are available via an FTP site, but then doesn't give an address, and I couldn't find one in the book—strange.
The book is divided into five parts. Not until Part 4 does Mr. Tansley actually begin to talk about programming. He expects the reader to know only how to log in and use a text editor. While this was a bit disappointing for me, it won't be for someone who has not worked with UNIX for as long as I have.
This book needed better editing; the mistakes I found should have been caught. Mr. Tansley has been a UNIX system administrator for some time and clearly knows his subject. But run-on sentences with improper punctuation, extra words, omitted words and misspellings (e.g., dirrectory) make understanding the material harder than it should be. An entire chapter is devoted to the find command, and it contains two serious editing problems. One, when explaining the use of the mtime option on page 25, this statement appears:
Use “-” to specify files that have not been accessed in x number of days. Use “+” for files that have been accessed.
This has the meanings of - and + reversed, as is demonstrated in his printed examples. Two, in his explanation of the exec option, there is this statement:
To use exec you do have to have the “-print” option on.
In general, the explanations are good, though not heavily detailed. The author's style is casual and simple, making it easy to read and understand. He discusses many useful things such as find, cron, grep, wild cards, pipes, input/output, awk, sed, environment variables and many shell commands. All this is a prelude to getting down to the serious business of scripting.
Part 4 covers shell scripting, and Part 5 covers better shell scripting. Part 4 begins with explanations of how to use test and expr to determine file status and string evaluation—a very good place to start, indeed. Then he moves on to discuss flow control structures (e.g., if-then-else, for, while and case), exit status, creation of menus and printing. Examples are simple and to the point, demonstrating the current topic quite aptly. A good example is how to make your script interactive; that is, accept input from the keyboard rather than run in the background. Also in Part 4, he covers passing parameters, creating screen input, debugging and built-in commands.
Part 5 goes on to advanced scripting, with more details on “here” files and how-tos for run-level and cgi scripts. He includes a goodly sample of his own administration scripts which are quite helpful. There is much useful information in these two sections to help the beginning scripter. I did not find technical errors in these parts as I did in the beginning.
LINUX & UNIX Shell Programming is a good introduction to the shell as well as scripting. With a good editor, it will be even better in a second edition. Right now, I hesitate to recommend it to complete beginners, even though they are its target audience; however, for someone who has used UNIX for a short while and has the ability to sort out any confusions caused by typos, it could provide a useful reference.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
- SUSE LLC's SUSE Manager
- My +1 Sword of Productivity
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Managing Linux Using Puppet
- Non-Linux FOSS: Caffeine!
- Doing for User Space What We Did for Kernel Space
- SuperTuxKart 0.9.2 Released
- Parsing an RSS News Feed with a Bash Script
- Google's SwiftShader Released
- SourceClear Open
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide