CPAN(3)
NNAAMMEE
CPAN - query, download and build perl modules from CPAN
sites
SSYYNNOOPPSSIISS
Interactive mode:
perl -MCPAN -e shell;
Batch mode:
use CPAN;
autobundle, clean, install, make, recompile, test
DDEESSCCRRIIPPTTIIOONN
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.
IInntteerraaccttiivvee MMooddee
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.
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 Knig
cpan> a /andk/
Author id = ANDK
EMAIL a.koenig@franz.ww.TU-Berlin.DE
FULLNAME Andreas Knig
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.
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.
CCPPAANN::::SShheellll
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.
aauuttoobbuunnddllee
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.
rreeccoommppiillee
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 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.
TThhee ffoouurr CCPPAANN::::** 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.
PPrrooggrraammmmeerr''ss iinntteerrffaaccee
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.
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 ", $mod->id, "\n";
}
MMeetthhooddss iinn tthhee ffoouurr
CCaacchhee MMaannaaggeerr
Currently the cache manager only keeps track of the build
directory ($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.
BBuunnddlleess
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.
PPrreerreeqquuiissiitteess
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
+o 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 $VERSION
variable . Currently all programs that are dealing with
version use something like this
perl -MExtUtils::MakeMaker -le \
'print MM->parse_version($ARGV[0])' filename
If you are author of a package and wonder if your
$VERSION can be parsed, please try the above method.
+o 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).
DDeebbuuggggiinngg
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.
FFllooppppyy,, ZZiipp,, aanndd aallll tthhaatt JJaazzzz
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.
CCOONNFFIIGGUURRAATTIIOONN
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 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.
CCDD--RROOMM ssuuppppoorrtt
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.
SSEECCUURRIITTYY
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.
EEXXPPOORRTT
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.
BBUUGGSS
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.
AAUUTTHHOORR
Andreas Knig lt;a.koenig@mind.de
SSEEEE AALLSSOO
perl(1), CPAN::Nox(3)