CPAN Module Distributions

a Perl script that generates a Makefile appropriate for the system where the module 

is being installed.

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What's a Makefile?

If you don't come from a UNIX programming background, you might not be 

familiar with Makefiles. A Makefile is a script processed by a program called 

make.

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 When make is run, it automatically looks for a file called Makefile in the 

current directory. make uses the information stored in the Makefile to perform the 

steps necessary to build and install programs from source files. To accomplish 

this task, a Makefile specifies a set of rules and dependencies.

A Makefile rule is a particular step in the build process examples of rules you've 

seen so far include  test  and  install . When you run the command make test,

you're instructing make to run the  test  rule in the Makefile. Makefiles also sup 

port the notion of a default rule that is run when no rule is explicitly specified, 

usually called  all .

Aside from rules that specify activities such as make test and make install,

Makefiles also have rules for creating files. One example of this type of rule is the 

one used to turn a module's POD documentation into a UNIX manual page 

through the pod2man program.

Makefiles combine rules by laying out rule dependencies. For example, the  all  

rule depends on the rule to build manual pages from POD documentation, among 

others. Dependencies work in two ways. First, they specify a series of steps 

describing how to complete a requested rule. Second, they allow make to intelli 

gently skip rules when it can tell that the target is up to date. For example, make

can tell that it doesn't need to rerun pod2man unless the module file containing the 

POD has been changed since the last time pod2man was run.

For more information about how Makefiles work on your system, see the docu 

mentation for your make command.

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The Makefile.PL that h2xs generates (see Listing 4 3) for Data::Counter is a 

simple Perl script. The script uses a single module ExtUtils::MakeMaker.

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 The 

subroutine WriteMakefile() is exported from ExtUtils::MakeMaker by default.

9. Or, on Microsoft Windows systems, possibly dmake or nmake. See the  Installing CPAN 

Modules  section in Chapter 1 for details.

10. Written by Andy Dougherty, Andreas Koenig, Tim Bunce, Charles Bailey and Ilya 

Zakharevich. It is included with Perl.

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