


CPAN(3p)         Perl Programmers Reference Guide        CPAN(3p)


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.

       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.







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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::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

       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-
         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 Konig

             cpan> a /andk/
             Author id = ANDK
                 EMAIL        a.koenig@franz.ww.TU-Berlin.DE
                 FULLNAME     Andreas Konig

             cpan> a /and.*rt/
             Author          ANDYD (Andy Dougherty)
             Author          MERLYN (Randal L. Schwartz)


       make, test, install, clean  modules or distributions
         These commands take any number of arguments and



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         investigates 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
         module is included and processes that, following any
         dependencies named in the module's Makefile.PL (this
         behavior is controlled by prerequisites_policy.)

         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, look module or distribution
         These two commands take only one argument, be it a
         module or a distribution file. 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.




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       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
         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.

       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. 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



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       should try the CPAN::Nox module for recovery.

       The four CPAN::* Classes: Author, Bundle, Module,
       Distribution

       Although 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.

       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(...)).

       There's currently only one class that has a stable
       interface - CPAN::Shell. All commands that are available



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       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 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-
       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



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       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
       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.




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       Finding packages and VERSION

       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 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(shift)' 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).

       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
       support.

       Floppy, Zip, Offline Mode

       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



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       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)
         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>
         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





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       o conf <list option> [unshift|push|splice] <list>
         works like the corresponding perl commands.

       urllist parameter has 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 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.

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 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
       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 re 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



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       then simply say

           cpan> install Bundle::my_bundle

       then answer a few questions and then go out.

       Maintaining a bundle definition file means to keep track
       of two things: dependencies and interactivity. CPAN.pm
       (currently) does not take into account dependencies
       between distributions, so a bundle definition file should
       specify distributions that depend on others after the
       others.  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 firewall
       following howto.

       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 you must 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
            firewall.

            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
            serves 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



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            connections 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
                 kernel, it allows you to hide a complete network
                 behind one IP address. With this firewall no
                 special 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
       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 Konig <a.koenig@kulturbox.de>

SEE ALSO
       perl(1), CPAN::Nox(3)


















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