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CPAN - query, download and build perl modules from CPAN sites |
CPAN::* Classes: Author, Bundle, Module, Distribution
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.
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 available in CPAN authors directories. If CPAN::WAIT
is installed on your system, the interactive shell of <CPAN.pm> 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.
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 with the rather verbose method as_string, but if we find
more than one, we display each object with the terse method
<as_glimpse>.
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&39;t need to be updated.
CPAN also keeps track of what it has done within the current session
and doesn&39;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 downloads a distribution file without further action. readme
displays the README file of the associated distribution. Look gets
and untars (if not yet done) the distribution file, changes to the
appropriate directory and opens a subshell process in that directory.
^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 usually means by
pressing ^C twice.
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&39;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) also return a list of
the IDs of all modules within the list.
expand($type,@things)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";
}
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 $mod->uptodate;
# new mod_perl arrived, let me know all update recommendations
CPAN::Shell->r;
Currently the cache manager only keeps track of the build directory
($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
perl -MExtUtils::MakeMaker -le \
'print MM->parse_version(shift)' 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. See also below the paragraph about CD-ROM support.
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_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.
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>o conf <scalar option> <value>o conf <list option>o conf <list option> [shift|pop]o conf <list option> [unshift|push|splice] <list>
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 format. Either:
file://localhost/whatever/ftp/pub/CPAN/
or
file:///home/ftp/pub/CPAN/
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.
Another peculiarity of urllist is that the site that we could successfully fetch the last file from automatically 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 disallow a site for the next transfer, it must be explicitly removed from urllist.
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 authentication.
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.
To populate a freshly installed perl with my favorite modules 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 definition 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_bundle.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.
Thanks to Graham Barr for contributing the following paragraphs about the interaction between perl, and various firewall configurations.
Firewalls can be categorized into three basic types.
To access servers outside these types of firewalls with perl (even for ftp) you will need to use LWP.
To access servers outside these type of firewalls with perl you will need to use Net::FTP.
There are two that I can think off.
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 Koenig <andreas.koenig@anima.de>
perl(1), CPAN::Nox(3)
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CPAN - query, download and build perl modules from CPAN sites |