CPAN - query, download and build perl modules from CPAN sites
Interactive mode:
perl -MCPAN -e shell;
Batch mode:
use CPAN;
autobundle, clean, install, make, recompile, test
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.
The interactive mode is entered by running
perl -MCPAN -e shell
which puts you into a readline interface. You will have the most fun if you install Term::ReadKey and Term::ReadLine to enjoy both history and command completion.
Once you are on the command line, type 'h' and the rest should be self-explanatory.
The most common uses of the interactive modes are
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 exactly matching 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 regular 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, the result is displayed as 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 König
cpan> a /andk/
Author id = ANDK
EMAIL a.koenig@franz.ww.TU-Berlin.DE
FULLNAME Andreas König
cpan> a /and.*rt/
Author ANDYD (Andy Dougherty)
Author MERLYN (Randal L. Schwartz)
Any make or test are run unconditionally. An
install <distribution_file>
also is run unconditionally. But for
install <module>
CPAN checks if an install is actually needed for it and prints module up to date in the case that the distribution file containing the module doesn't need to be updated.
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 a 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
[...]
A clean command results in a
make clean
being executed within the distribution file's working directory.
readme unconditionally runs, displaying 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.pm ignores a
SIGPIPE. If the user sets inactivity_timeout, a
SIGALRM is used during the run of the
perl Makefile.PL subprocess.
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 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() 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. The 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 invoke CPAN's recompile on the second
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.
CPAN::* Classes: Author, Bundle, Module, DistributionAlthough it may be considered internal, the class hierarchy does matter for both users and programmer. CPAN.pm deals with above mentioned four classes, and all those classes share a set of methods. A classical single polymorphism 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 the really hottest and newest distribution file is not always the default. 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. 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.
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(...)).
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.
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.
# 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 ", $mod->id, "\n";
}
Currently the cache manager only keeps track of the build directory ($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, then your sources will be deleted with the same fifo mechanism.
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 being 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 (e.g. 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.
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 far too much
memory to load all packages into the running program just to determine the
$VERSION variable. Currently all programs that are dealing
with version use something like this
perl -MExtUtils::MakeMaker -le \
'print MM->parse_version($ARGV[0])' filename
If you are author of a package and wonder if your $VERSION can
be parsed, please try the above method.
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 by-product 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.
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.
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:
build_cache size of cache for directories to build modules
build_dir locally accessible directory to build modules
index_expire after this 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 this
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 directory in which to keep the source (if we do)
make location of external make program
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)
wait_list arrayref to a wait server to try (See CPAN::WAIT)
You can set and query each of these options interactively in the cpan shell
with the command set defined within the o conf command:
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 there is a local copy of the most recent version.
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.
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.
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.
If a Makefile.PL requires special customization of libraries, prompts the user for special input, etc. then you may find CPAN is not able to build the distribution. In that case, you should attempt the traditional method of building a Perl module package from a shell.
Andreas König <a.koenig@mind.de>
perl(1), CPAN::Nox(3)
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.