Minimal Perl for Unix and Linux People

Ravi writes "Perl (Practical Extraction and Report Language) — the language which was created by Larry Wall is arguably one of the greatest programming languages. But it has a reputation for taking an excessive cryptic nature which gives it an image especially among Perl novices as a language which is complex and hard to master. Minimal Perl: for Unix and Linux people, authored by Tim Maher and published by Manning Publications addresses the obstacles presented by Perl's complexity. This book which is divided into two parts comprising of a total of 12 chapters takes a unique methodology to explain the Perl syntax and its use. The author emphasizes on Perl's grep, awk and sed like features and relys on concepts such as inputs, filters and arguments to allow Unix users to directly apply their existing knowledge to the task of learning Perl." Read on for the rest of Ravi's review. Minimal Perl for Unix and Linux People author Tim Maher pages 464 publisher Manning Publications rating 8 reviewer Ravi ISBN 1932394508 summary Provides a slice of Perl which when mastered can accomplish most of the jobs which require Perl What I found while reading this book is that the "Minimal Perl" is a specially crafted subset of Perl language designed to be easily grasped by people who have a Unix background and who wish to use Perl to write their scripts. Its aim is to filter out the complex way of writing programs using Perl and whenever possible to accomplish tasks using just one or two lines of Perl. In the first part of the book, the author explains how Perl can be used to do the same tasks as accomplished by common Unix tools such as grep, awk, sed and find. He goes one step further by explaining how one can accomplish much more and in a much simpler way by using Perl techniques.

Throughout the book, the author makes sure that the learning curve in acquiring Perl skills remain gentle. Perl is a language whose syntax has a multitude of options, this book is peppered with numerous tables which provide excellent information at a glance. For example, in the third chapter titled "Perl as a (Better) grep command", the author lists and compares the fundamental capabilities of Perl and the different grep commands such as grep, egrep and fgrep which clearly shows the advantages that Perl has over grep. In another table, you get a birds eye view of the essential syntax of Perl's regular expressions and their meaning. This chapter alone has around 12 tables. This is a really nice feature because it doubles as a Perl reference where you can flip to the respective page and get the information you need.

The main strength and drawback of a language such as Perl is its dependence on regular expressions for accomplishing complex tasks. Once you master the regular expressions, the sky is the limit for ordering and segregating data using this language. In Perl, there is more than one way of doing the same thing. What is unique about this book is that the author specializes in explaining the easiest way of doing a particular task.

In many places, the author demonstrates complex tasks using just a few lines of Perl code. Many of the examples covered in this book are practical examples which give an idea of how the commands relate to the final outcome. For instance, while elaborating on the one line grep like commands in Perl, the author illustrates a web oriented application of pattern matching where he shows how to extract and list, the outline of slashdot.org site's front page. The surprising thing is this is accomplished using just a single line of Perl code. This book has lots of such one line examples which teache how to use Perl intelligently using minimal effort.

If part I of this book focuses on ways in which simple Perl programs can provide superior alternatives to standard Unix commands, the second part throws light on the other aspects of Perl concentrating on the syntax of the language and various built-in functions and modules available which do away with a lot of re-invention of the wheel, so to speak, and helps churn out code which is portable.

Chapter 7 titled "Built-in functions" introduces an eclectic mix of functions available in Perl. You have functions which are used to extract a list of fields from a string, functions to access the current date and time, generating random numbers, sorting lists, transforming lists, managing files with functions and so on. These functions are broadly classified into those which generate and process scalars and those that process lists.

In chapter 8 of this book, the author involves the reader on the numerous scripting techniques that can be used to write better Perl programs.

It was quite surprising that the author has chosen to discuss the variables, more specifically the list variables comprising of arrays and hashes, as well as the looping constructs only in the 9th and 10th chapters, when they should be somewhere up front. In hind sight, I feel it is a good decision. Once you execute the one liner Perl programs in the initial chapters, you will be fairly confident in using Perl by the time you reach the 9th chapter.

The last two chapters deal with creating sub-routines and modules. Over the years various Perl programmers have created modules which are used for diverse purposes. With an aim to share these modules, they are collected and stored at one central place known as CPAN, which is an acronym for Comprehensive Perl Archive Network. The final chapter, apart from teaching how to create modules in Perl and manage them, also introduces the CPAN and ways in which one can find the right module by searching on CPAN.

The special variables cheat-sheet and the guidelines for parenthesizing code provided in the two appendices are really useful as a quick reference while writing Perl programs.

This is not a comprehensive book on Perl, rather the author provides a slice of Perl which when mastered can accomplish most of the jobs which require Perl. You won't find object oriented concepts of Perl being mentioned in this book. In many ways the author has moved beyond explaining a subset of Perl by providing a section titled "Directions for further study" at the end of each chapter, where the author lists further material which can be used to learn more about the topic that is covered.

I really enjoyed going through this book, especially because of its focus on the practical side of using Perl and taking a minimal approach.

Ravi Kumar maintains a blog titled "All about Linux" where he shares his thoughts and experiences in using Linux, Open Source and Free software.

You can purchase Minimal Perl for Unix and Linux People from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

*sigh*

[A beautiful mind]

Perl (Practical Extraction and Report Language)

That's a backronym. By those standards you could also call PHP Pretty Hellish Performance.

Re:*sigh*

[grcumb]

Perl (Practical Extraction and Report Language)

That's a backronym. By those standards you could also call PHP Pretty Hellish Performance.

ITYM 'Poorly Hung Perl'. 8^)

Cryptic? Complex!?

[setirw]

But it has a reputation for taking an excessive cryptic nature which gives it an image especially among Perl novices as a language which is complex and hard to master.

So wrong! Just look at the following example:

#!/usr/bin/perl -w

length q caller vec and print chr oct ord q qx eq and print chr ord q ref or and print chr ord q or no and print chr ord q else and print chr ord qq q q and print chr ord q tie gt and print chr ord qw q sin q and print chr ord q q eq and print chr ord qw q sin q and print chr ord q sin s and print chr ord q cmp lc and print chr ord q split s and print chr ord qw q lc q and print chr ord q ne sin and print chr hex length q q bless localtime ref q

Run that. Nothing cryptic or complex at all.

(BTW, it prints "Perl is simple!")

I {} Perl

[Cally]

perl has paid my rent and bought me more of the special, special tea from high in the Himalayas that enabled me to understand it so easily in the first place. I find myself speaking it in my sleep (and yes, you do speak Perl, just as you program in C.) It's a matter of some puzzlement to me that the loathesome homunculous that is PHP supplanted Perl as the preferred language for non-ASP web programming. (And ASP..? Don't get me started!!) I wrote my first code many years before discovering Perl, but it was Perl that turned me into a programmer. To me, you cannot claim to know Unix until you can read Perl (in both directions - in and out.)

That is all...

Re:I {} Perl

[timster]

"Speak" Perl, right. Because what Unix really needed was a combination of the specificity of natural language and the friendly syntax of awk.

Re:PERL backronym

[morgan_greywolf]

Nope.

Stands for Python'll Eventually Replace this Language.

or, optionally:

Perl Eats Ruby for Lunch :-D

Re:So you like the book

[realmolo]

8/10 is a *good* review. You've been reading too many IGN game reviews.

IGN scoring works like this:

5/10 - The game runs

6/10 - The game is an FPS

7/10 - The game has team-based mulitplayer online play

8/10 - The game runs at 190 frames-per-second

9/10 - The game is made by a publisher that buys advertising on IGN

10/10 - The game is made by a publisher that buys A LOT of advertising on IGN
 

Why not for Windows people?

[rrohbeck]

I think Windows folks need "Minimal Perl" a lot more.

Just remembering by boss's jaw drop when he asked me if I could do a quick analysis of a couple thousand lines of logs and asked how long it would take. "10 minutes." And I delivered. He thought I'd have to fire up VS and write some C code.

He borrowed my Camel book during his next vacation.

Re:Cryptic? Complex!?

[MoxFulder]

Run that. Nothing cryptic or complex at all.

Indeed! I used to be a die-hard hard-core Perl hacker. When I discovered Perl in college around 2001, I thought it was the greatest thing since sliced bread. And Perl really was revolutionary: you could do almost everything you could do in C, but more concisely, since you could create complex data structures without manual memory management.

I used Perl for fun and profit (wrote many Perl scripts for a speech software company) for many years, hanging on past the point where others started using Python, PHP, and Ruby instead. I knew Perl and could practically think in it. But one of the main problems with Perl is it's so easy to right totally unmaintainable, totally unreadable code. I read a Perl program I wrote a few years ago and I can never figure it out. The object-oriented part of Perl is a ridiculous kludge with so many little details that I can't remember them all. There are about 100 subtly different ways to write a constructor for your object:

sub new() {
    my ($class) = @_;
    my $self = {}
    return bless $self, $class
}

sub new() { return bless {} }

sub new() {
    my ($class) = @_
    my $self = {}
    bless $self, (ref $class || $class)
}

All of these, of course, have subtly different behaviors. The second will break inheritance. The third will allow you to use the constructor as an instance method, not just a class method. There are no enforced function prototypes or standard way to get parameters... and if you do use the *optional* prototype mechanism, you will subtly change the precedence of calls to your function.

I thought that having 1000 ways to do something was great, but it turns out to be a nightmare for non-trivial programs. Every time I try to use a cute fancy shortcut in Perl, it bites me in the ass. As a result of the over-flexibility, people have tried to impose "standards" on Perl. There are "standard" techniques for named parameters, "standard" techniques for accessor functions, etc. And that's nice, but Perl has 10,000+ available modules to do everything from screen-scrape Google news to access Oracle databases (it's greatest strength!!!). And not all those modules use the standard techniques.

About a year ago I decided to give Python a try. And I haven't looked back. It can do everything Perl can do, and then some. Everything is clearer and having a "standard" way to do most things makes learning new modules immensely easier. Having slightly more verbose syntax and strict type-checking is slightly annoying at first, but keeps me sane in the long run.

Basically I don't use perl for anything other than one-liner regexp tricks anymore. Stuff like perl -i -pe 's/FOO/BAR/g' *, which will change the string FOO to BAR in all the files in the current directory.

Not hard to learn, very easy to remember

[SCHecklerX]

The only 'strange' thing with Perl is its use of symbols to denote things. That is not really that big of a deal, and in fact makes working with code a bit easier, IMO, since you know loosely what type a variable is just by looking at it and the context of the code that surrounds it.

The thing I've noticed, as a Perl programmer, is that it is the *only* language I've ever used (amongst bash, c, c++, java, rexx, fortran, basic) that I can take a break from for a year, come back, and be able to write a simple script without the need to refer to any books or online manuals. That is VERY useful for those of us who are more sysadmins than programmers. This power is partly due to the "more than one way to do it" philosophy, that lets you program in a style that works for you, hence allowing you to remember *how* to write in that language.

Then again, that's what most anti-Perl folks bitch about. Any language can be obfuscated. If you write hard to decipher code in Perl, you'll write it that way in any language.

Picking Up Perl

[nbritton]

This: http://www.ebb.org/PickingUpPerl/pickingUpPerl.pdf guide is awesome if you want to learn Perl. Concise and articulate, it manages to explain all the major topics of Perl in 66 pages. I recommend working through the entire guide as quick as possible, don't worry about remembering everything as you can always come back to it later. I also recommend having the O'Reilly camel books (Learning Perl, Programming Perl, Perl Cookbook) handy when going through the guide. You can read the books here: http://www.jimsannex.com/Studies/CD_perl/index.htm but you better go out and buy the real thing, worth every penny!!! If your running Windows you'll need to download Perl and a good editor with syntax highlighting:

http://downloads.activestate.com/ActivePerl/Window s/5.8/ActivePerl-5.8.8.820-MSWin32-x86-274739.msi
http://www.crimsoneditor.com/

After you install perl open a command prompt and run ppm, this is your simple GUI gateway to CPAN packages (make a mental note). After you get a handle on basic perl checkout Perl/Tk (GUI Toolkit for Perl). The Tk packages are included and installed with ActivePerl... Here's your first Perl/TK program:

use Tk;
my $top = new MainWindow;
$top->configure(-title=>"My First Perl GUI Program");
my $lab = $top->Label(-textvariable=>\$labelText);
my $b = $top->Button(-text=>'Click Me!', -command=>sub {$labelText="Congratulations! it worked!" });
$lab->grid(-row=>0, -column=>0);
$b->grid(-row=>1, -column=>0);
MainLoop;

Re:Cryptic? Complex!?

[massysett]

Stuff like perl -i -pe 's/FOO/BAR/g' *, which will change the string FOO to BAR in all the files in the current directory.

Sed will do that too:

sed -i 's/FOO/BAR/g' *

The review says that the book uses the reader's knowledge of sed, awk, and grep. I figure: why not just use sed, awk, and grep...however, one advantage for Perl here is that (I presume) that line works with any Perl; '-i' is a GNU sed extension and may not work on non-GNU seds...

Re:oh come on, you're not even trying now

[fireboy1919]

You're not looking at it right.

KISS is hard. Very hard. It's different in different places. Sometimes keeping it simple means writing less code. Sometimes it means creating a new sub-language that better describes your problem.

In perl, you can change the nature of the language itself. *Everything* can be changed. The idea is that if there is more than one way to do it, then you can do it the simplest way for whatever definition of simple is required.

Maintaining consistency is up to the developer himself. Obviously, those tempted to succumb to the lure of sloppiness (which, unfortunately, in my experience, is every perl programmer I've ever met including myself) shouldn't use perl for really big projects.
You can't blame the language for giving you that freedom, though.

Perl is where it is because you don't have to change the way that you think in order to program in it. Perl will change how it works to match how you think, which makes it more convenient than almost any other language.

That particular behavior is what makes it possible to have so many perl modules in existane, which in turn is responsible for the popularity. It's also why about half of those modules have bugs so horrible that they're unusable. It's certainly a tradeoff.

Re:Very Minimal Perl for Unix People

[Tet]

This strips carriage returns out of a file, and does it pretty quickly.

No, it's horrendously slow. The traditional Unix way of doing it (tr -d '\015') is around twice as fast on files that are sufficiently large that startup costs are lost in the noise, and even faster on smaller files.

Re:Cryptic? Complex!?

[abigor]

His usage of "it's" is correct. It's = it is.