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Conventions Used in This Book

Programming Conventions

We are firm believers in using Perl's -w command-line option and its use strict pragma in every non-trivial program. We start nearly all our longer programs with:

#!/usr/bin/perl -w
use strict;

We give lots of examples, most of which are pieces of code that should go into a larger program. Some examples are complete programs, which you can recognize because they begin with a #! line.

Still other examples are things to be typed on a command line. We've used % to indicate the shell prompt:

% perl -e 'print "Hello, world.\n"'

Hello, world.

This style is representative of a standard Unix command line. Quoting and wildcard conventions on other systems vary. For example, most standard command-line interpreters under DOS and VMS require double quotes instead of single ones to group arguments with spaces or wildcards in them. Adjust accordingly.

Typesetting Conventions

The following typographic conventions are used in this book:


is used for filenames, command names, and URLs. It is also used to define new terms when they first appear in the text.


is used for command-line options.

Constant Width

is used for function and method names and their arguments; in examples to show the text that you enter literally; and in regular text to show any literal code.

Constant Bold Italic

is used in examples to show output produced.

Documentation Conventions

The most up-to-date and complete documentation about Perl is included with Perl itself. If typeset and printed, this massive anthology would use more than a thousand pages of printer pager, greatly contributing to global deforestation. Fortunately, you don't have to print it out because it's available in a convenient and searchable electronic form.

When we refer to a "manpage" in this book, we're talking about this set of online manuals. The name is purely a convention; you don't need a Unix-style man program to read them. The perldoc command distributed with Perl also works, and you may even have the manpages installed as HTML pages, especially on non-Unix systems. Plus, once you know where they're installed, you can grep them directly.[ 1 ]The HTML version of the manpages is available on the Web at http://www.perl.com/CPAN/doc/manual/html/ .

[1] If your system doesn't have grep , use the tcgrep program supplied at the end of Chapter 6 .

When we refer to non-Perl documentation, as in "See kill (2) in your system manual," this refers to the kill manpage from section 2 of the Unix Programmer's Manual (system calls). These won't be available on non-Unix systems, but that's probably okay, because you couldn't use them there anyway. If you really do need the documentation for a system call or library function, many organizations have put their manpages on the Web; a quick search of AltaVista for + crypt(3) +manual will find many copies.