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.

    All methods provided are accessible in a programmer style and in an
    interactive shell style.

  Interactive Mode

    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.

  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.

  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.
    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.

  The 4 `CPAN::*' 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 he 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 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 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

  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
    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, 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.

    There is a meaningless Bundle::Demo available on CPAN. Try to install
    it, it usually does no harm, just demonstrates what the Bundle interface
    looks like.

  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.

    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 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.

    * 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 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.

  Floppy, Zip, and all that Jazz

    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 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.

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 authentification.

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.

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 intergration of
    the other parts.

AUTHOR
    Andreas Knig <a.koenig@mind.de>

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

