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8.46. CPAN
Lets you
access CPAN; search for a module, a bundle, an author, or a
distribution; download a module or distribution; install it; and
make it. The CPAN module can be used either
interactively from the command line or programmatically:
perl -MCPAN -eshell; # Run from the command line
or:
use CPAN;
my $obj = CPAN::Shell->install('ExtUtils::MakeMaker');
This section describes the use of the CPAN module from a program. See
Chapter 2, "Installing Perl" for information on using it
interactively and for details of the available commands. These
commands, available interactively from the shell, are methods of the
class CPAN::Shell. From a program, they are available both as methods
(e.g., CPAN::Shell->install(...)) and as
functions in the calling package (e.g.,
install(...)).
Each of the commands that produce listings of modules
(r, autobundle, and
u) returns a list of the IDs of all modules within
the list. The IDs of all objects available within a program are
strings that can be expanded to the corresponding real objects with
the CPAN::Shell->expand("Module",@things)
method. expand returns a list of CPAN::Module
objects according to the @things arguments. In
scalar context, it returns only the first element of the list.
8.46.1. Session and Cache Managers
The CPAN module contains a session manager, which keeps track of
objects that have been fetched, built, and installed in the current
session. No status is retained between sessions.
There is also a cache manager, which keeps track of disk space used
and deletes extra space. The cache manager keeps track of the build
directory, $CPAN::Config->{build_dir}, and uses
a simple FIFO mechanism to delete directories below
build_dir when they grow bigger than
$CPAN::Config->{build_cache}.
The original distribution files are kept in the directory
$CPAN::Config->{keep_source_where}. This
directory is not covered by the cache manager but must be controlled
by the user. If the same directory is used as both
build_dir and
keep_source_where, your sources are deleted with
the same FIFO mechanism.
8.46.2. Bundles
The CPAN module recognizes a bundle as a Perl module in the namespace
Bundle:: that does not define any functions or methods and usually
contains only pod documentation. It starts like a Perl module with a
package declaration and a $VERSION variable. After
that, the pod section looks like any other pod except that it
contains a special section that begins with:
=head1 CONTENTS
This section consists of lines such as:
Module_Name [Version_String] [- optional text]
in which Module_Name is the name of a
module (for example, Term::ReadLine), not the name of a distribution
file, and the version and text are optional. If there is text, it is
preceded by a -. The distribution of a bundle
should follow the same convention as other distributions.
Bundles are treated specially in the CPAN package. When you tell CPAN
to install a bundle, it installs all the modules in the CONTENTS
section of the pod. You can install your own bundles locally by
placing a conforming bundle file somewhere in your
@INC path. The autobundle
command available in the shell interface does that for you by
including all currently installed modules in a snapshot bundle file
(see Chapter 2, "Installing Perl").
8.46.3. Configuration
When the CPAN module is installed, a site-wide configuration file is
created: CPAN/Config.pm. The default values
defined there can be overridden locally in the file
CPAN/MyConfig.pm. You can store this file in
$HOME/.cpan/CPAN/MyConfig.pm, because
$HOME/.cpan is added to the search path of the
CPAN module before the use or
require statements. Chapter 2, "Installing Perl"
lists the keys defined in the hash reference
$CPAN::Config and how to set and query them.
8.46.4. CD-ROM Support
The urllist parameter
in the configuration table contains a list of URLs that will be used
for downloading. If the list contains any file
URLs, CPAN looks there first for files (except index files). So if
you are using a CD-ROM containing the CPAN contents, include the
CD-ROM as a file URL at the end of
urllist since it is likely to be out-of-date.
You can do this with:
o conf urllist push file://localhost/CDROM/CPAN
