


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 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
       <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::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 <as_glimpse>.

       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 <distribution_file>

         also is run unconditionally. But for

           install <module>




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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

       o 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.

       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



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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 <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 Make-
         Maker'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.

       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 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 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 <andreas.koenig@anima.de>

SEE ALSO
       perl(1), CPAN:\fIs0:Nox(3)







































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