CPAN(3) CPAN(3)
NAME
CPAN - query, download and build perl modules from CPAN sites
SYNOPSIS
Interactive mode:
perl -MCPAN -e shell;
Batch mode:
use CPAN;
autobundle, clean, install, make, recompile, test
DESCRIPTION
The CPAN module is designed to automate the make and install of perl
modules and extensions. It includes some searching capabilities and knows
how to use Net::FTP or LWP (or lynx or an external ftp client) to fetch
the raw data from the net.
Modules are fetched from one or more of the mirrored CPAN (Comprehensive
Perl Archive Network) sites and unpacked in a dedicated directory.
The CPAN module also supports the concept of named and versioned
'bundles' of modules. Bundles simplify the handling of sets of related
modules. See BUNDLES below.
The package contains a session manager and a cache manager. There is no
status retained between sessions. The session manager keeps track of what
has been fetched, built and installed in the current session. The cache
manager keeps track of the disk space occupied by the make processes and
deletes excess space according to a simple FIFO mechanism.
All methods provided are accessible in a programmer style and in an
interactive shell style.
Interactive Mode
The interactive mode is entered by running
perl -MCPAN -e shell
which puts you into a readline interface. You will have most fun if you
install Term::ReadKey and Term::ReadLine to enjoy both history and
completion.
Once you are on the command line, type 'h' and the rest should be self-
explanatory.
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The most common uses of the interactive modes are
Searching for authors, bundles, distribution files and modules
There are corresponding one-letter commands a, b, d, and m for each of
the four categories and another, i for any of the mentioned four. Each
of the four entities is implemented as a class with slightly differing
methods for displaying an object.
Arguments you pass to these commands are either strings matching exact
the identification string of an object or regular expressions that are
then matched case-insensitively against various attributes of the
objects. The parser recognizes a regualar expression only if you
enclose it between two slashes.
The principle is that the number of found objects influences how an
item is displayed. If the search finds one item, we display the result
of object->as_string, but if we find more than one, we display each as
object->as_glimpse. E.g.
cpan> a ANDK
Author id = ANDK
EMAIL a.koenig@franz.ww.TU-Berlin.DE
FULLNAME Andreas Kvnig
cpan> a /andk/
Author id = ANDK
EMAIL a.koenig@franz.ww.TU-Berlin.DE
FULLNAME Andreas Kvnig
cpan> a /and.*rt/
Author ANDYD (Andy Dougherty)
Author MERLYN (Randal L. Schwartz)
make, test, install, clean modules or distributions
These commands do indeed exist just as written above. Each of them
takes any number of arguments and investigates for each what it might
be. Is it a distribution file (recognized by embedded slashes), this
file is being processed. Is it a module, CPAN determines the
distribution file where this module is included and processes that.
Any make, test, and readme are run unconditionally. A
install <distribution_file>
also is run unconditionally. But for
install <module>
CPAN checks if an install is actually needed for it and prints Foo up
to date in case the module doesn't need to be updated.
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CPAN also keeps track of what it has done within the current session
and doesn't try to build a package a second time regardless if it
succeeded or not. The force command takes as first argument the method
to invoke (currently: make, test, or install) and executes the command
from scratch.
Example:
cpan> install OpenGL
OpenGL is up to date.
cpan> force install OpenGL
Running make
OpenGL-0.4/
OpenGL-0.4/COPYRIGHT
[...]
readme, look module or distribution
These two commands take only one argument, be it a module or a
distribution file. readme displays the README of the associated
distribution file. Look gets and untars (if not yet done) the
distribution file, changes to the appropriate directory and opens a
subshell process in that directory.
CPAN::Shell
The commands that are available in the shell interface are methods in the
package CPAN::Shell. If you enter the shell command, all your input is
split by the Text::ParseWords::shellwords() routine which acts like most
shells do. The first word is being interpreted as the method to be called
and the rest of the words are treated as arguments to this method.
Continuation lines are supported if a line ends with a literal backslash.
autobundle
autobundle writes a bundle file into the $CPAN::Config-
>{cpan_home}/Bundle directory. The file contains a list of all modules
that are both available from CPAN and currently installed within @INC.
The name of the bundle file is based on the current date and a counter.
recompile
recompile() is a very special command in that it takes no argument and
runs the make/test/install cycle with brute force over all installed
dynamically loadable extensions (aka XS modules) with 'force' in effect.
Primary purpose of this command is to finish a network installation.
Imagine, you have a common source tree for two different architectures.
You decide to do a completely independent fresh installation. You start
on one architecture with the help of a Bundle file produced earlier. CPAN
installs the whole Bundle for you, but when you try to repeat the job on
the second architecture, CPAN responds with a "Foo up to date" message
for all modules. So you will be glad to run recompile in the second
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architecture and you're done.
Another popular use for recompile is to act as a rescue in case your perl
breaks binary compatibility. If one of the modules that CPAN uses is in
turn depending on binary compatibility (so you cannot run CPAN commands),
then you should try the CPAN::Nox module for recovery.
The four CPAN::* Classes: Author, Bundle, Module, Distribution
Although it may be considered internal, the class hierarchie does matter
for both users and programmer. CPAN.pm deals with above mentioned four
classes, and all those classes share a set of methods. It is a classical
single polymorphism that is in effect. A metaclass object registers all
objects of all kinds and indexes them with a string. The strings
referencing objects have a separated namespace (well, not completely
separated):
Namespace Class
words containing a "/" (slash) Distribution
words starting with Bundle:: Bundle
everything else Module or Author
Modules know their associated Distribution objects. They always refer to
the most recent official release. Developers may mark their releases as
unstable development versions (by inserting an underbar into the visible
version number), so not always is the default distribution for a given
module the really hottest and newest. If a module Foo circulates on CPAN
in both version 1.23 and 1.23_90, CPAN.pm offers a convenient way to
install version 1.23 by saying
install Foo
This would install the complete distribution file (say BAR/Foo-
1.23.tar.gz) with all accompanying material in there. But if you would
like to install version 1.23_90, you need to know where the distribution
file resides on CPAN relative to the authors/id/ directory. If the author
is BAR, this might be BAR/Foo-1.23_90.tar.gz, so you would have to say
install BAR/Foo-1.23_90.tar.gz
The first example will be driven by an object of the class CPAN::Module,
the second by an object of class CPAN::Distribution.
Programmer's interface
If you do not enter the shell, the available shell commands are both
available as methods (CPAN::Shell->install(...)) and as functions in the
calling package (install(...)).
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There's currently only one class that has a stable interface,
CPAN::Shell. All commands that are available in the CPAN shell are
methods of the class CPAN::Shell. Each of the commands that produce
listings of modules (r, autobundle, u) returns a list of the IDs of all
modules within the list.
expand($type,@things)
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 given. In scalar context it
only returns the first element of the list.
Programming Examples
This enables the programmer to do operations that combine
functionalities that are available in the shell.
# install everything that is outdated on my disk:
perl -MCPAN -e 'CPAN::Shell->install(CPAN::Shell->r)'
# install my favorite programs if necessary:
for $mod (qw(Net::FTP MD5 Data::Dumper)){
my $obj = CPAN::Shell->expand('Module',$mod);
$obj->install;
}
# list all modules on my disk that have no VERSION number
for $mod (CPAN::Shell->expand("Module","/./")){
next unless $mod->inst_file;
# MakeMaker convention for undefined $VERSION:
next unless $mod->inst_version eq "undef";
print "No VERSION in ", $mod->id, "\n";
}
Methods in the four
Cache Manager
Currently the cache manager only keeps track of the build directory
($CPAN::Config->{build_dir}). It is a simple FIFO mechanism that deletes
complete directories below build_dir as soon as the size of all
directories there gets bigger than $CPAN::Config->{build_cache} (in MB).
The contents of this cache may be used for later re-installations that
you intend to do manually, but will never be trusted by CPAN itself. This
is due to the fact that the user might use these directories for building
modules on different architectures.
There is another directory ($CPAN::Config->{keep_source_where}) where the
original distribution files are kept. This directory is not covered by
the cache manager and must be controlled by the user. If you choose to
have the same directory as build_dir and as keep_source_where directory,
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then your sources will be deleted with the same fifo mechanism.
Bundles
A bundle is just a perl module in the namespace Bundle:: that does not
define any functions or methods. It usually only contains 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 with the
only difference, that one special pod section exists starting with
(verbatim):
=head1 CONTENTS
In this pod section each line obeys the format
Module_Name [Version_String] [- optional text]
The only required part is the first field, the name of a module (eg.
Foo::Bar, ie. not the name of the distribution file). The rest of the
line is optional. The comment part is delimited by a dash just as in the
man page header.
The distribution of a bundle should follow the same convention as other
distributions.
Bundles are treated specially in the CPAN package. If you say 'install
Bundle::Tkkit' (assuming such a bundle exists), CPAN will install all the
modules in the CONTENTS section of the pod. You can install your own
Bundles locally by placing a conformant Bundle file somewhere into your
@INC path. The autobundle() command which is available in the shell
interface does that for you by including all currently installed modules
in a snapshot bundle file.
Prerequisites
If you have a local mirror of CPAN and can access all files with "file:"
URLs, then you only need a perl better than perl5.003 to run this module.
Otherwise Net::FTP is strongly recommended. LWP may be required for non-
UNIX systems or if your nearest CPAN site is associated with an URL that
is not ftp:.
If you have neither Net::FTP nor LWP, there is a fallback mechanism
implemented for an external ftp command or for an external lynx command.
This module presumes that all packages on CPAN
⊕ declare their $VERSION variable in an easy to parse manner. This
prerequisite can hardly be relaxed because it consumes by far too much
memory to load all packages into the running program just to determine
the $VERSION variable . Currently all programs that are dealing with
version use something like this
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perl -MExtUtils::MakeMaker -le \
'print MM->parse_version($ARGV[0])' filename
If you are author of a package and wonder if your $VERSION can be
parsed, please try the above method.
⊕ come as compressed or gzipped tarfiles or as zip files and contain a
Makefile.PL (well we try to handle a bit more, but without much
enthusiasm).
Debugging
The debugging of this module is pretty difficult, because we have
interferences of the software producing the indices on CPAN, of the
mirroring process on CPAN, of packaging, of configuration, of
synchronicity, and of bugs within CPAN.pm.
In interactive mode you can try "o debug" which will list options for
debugging the various parts of the package. The output may not be very
useful for you as it's just a byproduct of my own testing, but if you
have an idea which part of the package may have a bug, it's sometimes
worth to give it a try and send me more specific output. You should know
that "o debug" has built-in completion support.
Floppy, Zip, and all that Jazz
CPAN.pm works nicely without network too. If you maintain machines that
are not networked at all, you should consider working with file: URLs.
Of course, you have to collect your modules somewhere first. So you might
use CPAN.pm to put together all you need on a networked machine. Then
copy the $CPAN::Config->{keep_source_where} (but not
$CPAN::Config->{build_dir}) directory on a floppy. This floppy is kind of
a personal CPAN. CPAN.pm on the non-networked machines works nicely with
this floppy.
CONFIGURATION
When the CPAN module is installed a site wide configuration file is
created as CPAN/Config.pm. The default values defined there can be
overridden in another configuration file: CPAN/MyConfig.pm. You can store
this file in $HOME/.cpan/CPAN/MyConfig.pm if you want, because
$HOME/.cpan is added to the search path of the CPAN module before the
use() or require() statements.
Currently the following keys in the hash reference $CPAN::Config are
defined:
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build_cache size of cache for directories to build modules
build_dir locally accessible directory to build modules
index_expire after how many days refetch index files
cpan_home local directory reserved for this package
gzip location of external program gzip
inactivity_timeout breaks interactive Makefile.PLs after that
many seconds inactivity. Set to 0 to never break.
inhibit_startup_message
if true, does not print the startup message
keep_source keep the source in a local directory?
keep_source_where where keep the source (if we do)
make location of external program make
make_arg arguments that should always be passed to 'make'
make_install_arg same as make_arg for 'make install'
makepl_arg arguments passed to 'perl Makefile.PL'
pager location of external program more (or any pager)
tar location of external program tar
unzip location of external program unzip
urllist arrayref to nearby CPAN sites (or equivalent locations)
You can set and query each of these options interactively in the cpan
shell with the command set defined within the o conf command:
o conf <scalar option>
prints the current value of the scalar option
o conf <scalar option> <value>
Sets the value of the scalar option to value
o conf <list option>
prints the current value of the list option in MakeMaker's neatvalue
format.
o conf <list option> [shift|pop]
shifts or pops the array in the list option variable
o conf <list option> [unshift|push|splice] <list>
works like the corresponding perl commands.
CD-ROM support
The urllist parameter of the configuration table contains a list of URLs
that are to be used for downloading. If the list contains any file URLs,
CPAN always tries to get files from there first. This feature is disabled
for index files. So the recommendation for the owner of a CD-ROM with
CPAN contents is: include your local, possibly outdated CD-ROM as a file
URL at the end of urllist, e.g.
o conf urllist push file://localhost/CDROM/CPAN
CPAN.pm will then fetch the index files from one of the CPAN sites that
come at the beginning of urllist. It will later check for each module if
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there is a local copy of the most recent version.
SECURITY
There's no strong security layer in CPAN.pm. CPAN.pm helps you to install
foreign, unmasked, unsigned code on your machine. We compare to a
checksum that comes from the net just as the distribution file itself. If
somebody has managed to tamper with the distribution file, they may have
as well tampered with the CHECKSUMS file. Future development will go
towards strong authentification.
EXPORT
Most functions in package CPAN are exported per default. The reason for
this is that the primary use is intended for the cpan shell or for
oneliners.
BUGS
we should give coverage for _all_ of the CPAN and not just the PAUSE
part, right? In this discussion CPAN and PAUSE have become equal -- but
they are not. PAUSE is authors/ and modules/. CPAN is PAUSE plus the
clpa/, doc/, misc/, ports/, src/, scripts/.
Future development should be directed towards a better integration of the
other parts.
AUTHOR
Andreas Kvnig <a.koenig@mind.de>
SEE ALSO
perl(1), CPAN::Nox(3)
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