CPAN
CPAN(3pm) Perl Programmers Reference Guide CPAN(3pm)
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 han
dling of sets of related modules. See Bundles below.
The package contains a session manager and a cache man
ager. 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 man
ager keeps track of the disk space occupied by the make
processes and deletes excess space according to a simple
FIFO mechanism.
For extended searching capabilities there's a plugin for
CPAN available, the CPAN::WAIT manpage. `CPAN::WAIT' is a
full-text search engine that indexes all documents avail
able in CPAN authors directories. If `CPAN::WAIT' is
installed on your system, the interactive shell of
will enable the `wq', `wr', `wd', `wl', and `wh'
commands which send queries to the WAIT server that has
been configured for your installation.
All other methods provided are accessible in a programmer
style and in an interactive shell style.
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Interactive Mode
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::Read
Line 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
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
exactly matching the identification string of an object
or regular expressions that are then matched case-insen
sitively 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 influ
ences how an item is displayed. If the search finds one
item, the result is displayed with the rather verbose
method `as_string', but if we find more than one, we
display each object with the terse method .
make, test, install, clean modules or distributions
These commands take any number of arguments and investi
gate what is necessary to perform the action. If the
argument is a distribution file name (recognized by
embedded slashes), it is processed. If it is a module,
CPAN determines the distribution file in which this mod
ule is included and processes that, following any depen
dencies named in the module's Makefile.PL (this behavior
is controlled by prerequisites_policy.)
Any `make' or `test' are run unconditionally. An
install
also is run unconditionally. But for
install
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CPAN checks if an install is actually needed for it and
prints module up to date in the case that the distribu
tion 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.
get, readme, look module or distribution
`get' downloads a distribution file without further
action. `readme' displays the README file of the associ
ated distribution. `Look' gets and untars (if not yet
done) the distribution file, changes to the appropriate
directory and opens a subshell process in that direc
tory.
Signals
CPAN.pm installs signal handlers for SIGINT and SIGTERM.
While you are in the cpan-shell it is intended that you
can press `^C' anytime and return to the cpan-shell
prompt. A SIGTERM will cause the cpan-shell to clean up
and leave the shell loop. You can emulate the effect of
a SIGTERM by sending two consecutive SIGINTs, which usu
ally means by pressing `^C' twice.
CPAN.pm ignores a SIGPIPE. If the user sets inactiv
ity_timeout, a SIGALRM is used during the run of the
`perl Makefile.PL' subprocess.
CPAN::Shell
The commands that are available in the shell interface are
methods in the package CPAN::Shell. If you enter the shell
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command, all your input is split by the Text::Parse
Words::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 argu
ments to this method. Continuation lines are supported if
a line ends with a literal backslash.
autobundle
`autobundle' writes a bundle file into the `$CPAN::Con
fig->{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. The primary pur
pose 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.
The four `CPAN::*' Classes: Author, Bundle, Module, Dis
tribution
Although it may be considered internal, the class hierar
chy 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 poly
morphism 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
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Modules know their associated Distribution objects. They
always refer to the most recent official release. Develop
ers may mark their releases as unstable development ver
sions (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 circu
lates 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::Dis
tribution.
Programmer's interface
If you do not enter the shell, the available shell com
mands 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 inter
face - 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', `auto
bundle', `u') also return 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 com
bine functionalities that are available in the shell.
# install everything that is outdated on my disk:
perl -MCPAN -e 'CPAN::Shell->install(CPAN::Shell->r)'
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# 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";
}
Or if you want to write a cronjob to watch The CPAN, you
could list all modules that need updating:
perl -e 'use CPAN; CPAN::Shell->r;'
If you don't want to get any output if all modules are
up to date, you can parse the output of above command
for the regular expression //modules are up to date//
and decide to mail the output only if it doesn't match.
Ick?
If you prefer to do it more in a programmer style in one
single process, maybe something like this suites you
better:
# list all modules on my disk that have newer versions on CPAN
for $mod (CPAN::Shell->expand("Module","/./")){
next unless $mod->inst_file;
next if $mod->uptodate;
printf "Module %s is installed as %s, could be updated to %s from CPAN\n",
$mod->id, $mod->inst_version, $mod->cpan_version;
}
If that gives you too much output every day, you maybe
only want to watch for three modules. You can write
for $mod (CPAN::Shell->expand("Module","/Apache|LWP|CGI/")){
as the first line instead. Or you can combine some of
the above tricks:
# watch only for a new mod_perl module
$mod = CPAN::Shell->expand("Module","mod_perl");
exit if $mod->uptodate;
# new mod_perl arrived, let me know all update recommendations
CPAN::Shell->r;
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Methods in the four Classes
Cache Manager
Currently the cache manager only keeps track of the build
directory ($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 $CPAN::Config->{build_cache} (in MB). The
contents of this cache may be used for later re-installa
tions that you intend to do manually, but will never be
trusted by CPAN itself. This is due to the fact that the
user might use these directories for building modules on
different architectures.
There is another directory ($CPAN::Con
fig->{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.
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 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 distribu
tion 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 con
vention 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
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locally by placing a conformant Bundle file somewhere into
your @INC path. The autobundle() command which is avail
able 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.
Finding packages and VERSION
This module presumes that all packages on CPAN
· declare their $VERSION variable in an easy to parse man
ner. 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 vari
able. Currently all programs that are dealing with ver
sion use something like this
perl -MExtUtils::MakeMaker -le \
'print MM->parse_version(shift)' filename
If you are author of a package and wonder if your $VER
SION 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
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
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support.
Floppy, Zip, Offline Mode
CPAN.pm works nicely without network too. If you maintain
machines that are not networked at all, you should con
sider working with file: URLs. Of course, you have to col
lect 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.
See also below the paragraph about CD-ROM support.
CONFIGURATION
When the CPAN module is installed, a site wide configura
tion 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_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)
prerequisites_policy
what to do if you are missing module prerequisites
('follow' automatically, 'ask' me, or 'ignore')
scan_cache controls scanning of cache ('atstart' or 'never')
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)
ftp_proxy, } the three usual variables for configuring
http_proxy, } proxy requests. Both as CPAN::Config variables
no_proxy } and as environment variables configurable.
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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 '
prints the current value of the scalar option
`o conf '
Sets the value of the scalar option to value
`o conf '
prints the current value of the list option in Make
Maker's neatvalue format.
`o conf [shift|pop]'
shifts or pops the array in the list option variable
`o conf [unshift|push|splice] '
works like the corresponding perl commands.
Note on urllist parameter's format
urllist parameters are URLs according to RFC 1738. We do a
little guessing if your URL is not compliant, but if you
have problems with file URLs, please try the correct for
mat. Either:
file://localhost/whatever/ftp/pub/CPAN/
or
file:///home/ftp/pub/CPAN/
urllist parameter has CD-ROM support
The `urllist' parameter of the configuration table con
tains 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.
Another peculiarity of urllist is that the site that we
could successfully fetch the last file from automatically
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gets a preference token and is tried as the first site for
the next request. So if you add a new site at runtime it
may happen that the previously preferred site will be
tried another time. This means that if you want to disal
low a site for the next transfer, it must be explicitly
removed from urllist.
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 man
aged to tamper with the distribution file, they may have
as well tampered with the CHECKSUMS file. Future develop
ment will go towards strong authentication.
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.
POPULATE AN INSTALLATION WITH LOTS OF MODULES
To populate a freshly installed perl with my favorite mod
ules is pretty easiest by maintaining a private bundle
definition file. To get a useful blueprint of a bundle
definition file, the command autobundle can be used on the
CPAN shell command line. This command writes a bundle def
inition file for all modules that are installed for the
currently running perl interpreter. It's recommended to
run this command only once and from then on maintain the
file manually under a private name, say Bundle/my_bun
dle.pm. With a clever bundle file you can then simply say
cpan> install Bundle::my_bundle
then answer a few questions and then go out for a coffee.
Maintaining a bundle definition file means to keep track
of two things: dependencies and interactivity. CPAN.pm
sometimes fails on calculating dependencies because not
all modules define all MakeMaker attributes correctly, so
a bundle definition file should specify prerequisites as
early as possible. On the other hand, it's a bit annoying
that many distributions need some interactive configuring.
So what I try to accomplish in my private bundle file is
to have the packages that need to be configured early in
the file and the gentle ones later, so I can go out after
a few minutes and leave CPAN.pm unattained.
WORKING WITH CPAN.pm BEHIND FIREWALLS
Thanks to Graham Barr for contributing the following para
graphs about the interaction between perl, and various
firewall configurations.
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Firewalls can be categorized into three basic types.
http firewall
This is where the firewall machine runs a web server
and to access the outside world do it via the
web server. If you set environment variables like
http_proxy or ftp_proxy to a values beginning with
http:// or in your web browser you have to set proxy
information then you know you are running a http fire
wall.
To access servers outside these types of firewalls
with perl (even for ftp) you will need to use LWP.
ftp firewall
This where the firewall machine runs a ftp server.
This kind of firewall will only let you access ftp
servers outside the firewall. This is usually done by
connecting to the firewall with ftp, then entering a
username like "user@outside.host.com"
To access servers outside these type of firewalls with
perl you will need to use Net::FTP.
One way visibility
I say one way visibility as these firewalls try to
make themselve look invisible to the users inside the
firewall. An FTP data connection is normally created
by sending the remote server your IP address and then
listening for the connection. But the remote server
will not be able to connect to you because of the
firewall. So for these types of firewall FTP connec
tions need to be done in a passive mode.
There are two that I can think off.
SOCKS
If you are using a SOCKS firewall you will need to
compile perl and link it with the SOCKS library,
this is what is normally called a ``socksified''
perl. With this executable you will be able to
connect to servers outside the firewall as if it
is not there.
IP Masquerade
This is the firewall implemented in the Linux ker
nel, it allows you to hide a complete network
behind one IP address. With this firewall no spe
cial compiling is need as you can access hosts
directly.
BUGS
We should give coverage for all of the CPAN and not just
the PAUSE part, right? In this discussion CPAN and PAUSE
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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.
AUTHOR
Andreas Koenig
SEE ALSO
perl(1), CPAN:\fIs0:Nox(3)
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