CPAN(3) Perl Programmers Reference Guide CPAN(3)NAMECPAN - 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, "CPAN::WAIT". "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.
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 function call "shell" takes two optional arguments,
one is the prompt, the second is the default initial com
mand line (the latter only works if a real ReadLine inter
face module is installed).
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>
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.
ls author
"ls" lists all distribution files in and below an
author's CPAN directory. Only those files that contain
modules are listed and if there is more than one for any
given module, only the most recent one is listed.
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
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
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.
expandany(@things)
Like expand, but returns objects of the appropriate
type, i.e. CPAN::Bundle objects for bundles, CPAN::Mod
ule objects for modules and CPAN::Distribution objects
fro distributions.
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)'
# 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";
}
# find out which distribution on CPAN contains a module:
print CPAN::Shell->expand("Module","Apache::Constants")->cpan_file
Or if you want to write a cronjob to watch The CPAN, you
could list all modules that need updating. First a quick
and dirty way:
perl -e 'use CPAN; CPAN::Shell->r;'
If you don't want to get any output in the case that 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 suits you bet
ter:
# 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 $mod->uptodate;
# new mod_perl arrived, let me know all update recommendations
CPAN::Shell->r;
Methods in the other Classes
The programming interface for the classes CPAN::Module,
CPAN::Distribution, CPAN::Bundle, and CPAN::Author is
still considered beta and partially even alpha. In the
following paragraphs only those methods are documented
that have proven useful over a longer time and thus are
unlikely to change.
CPAN:s0:Author::as_glimpse()
Returns a one-line description of the author
CPAN:s0:Author::as_string()
Returns a multi-line description of the author
CPAN:s0:Author::email()
Returns the author's email address
CPAN:s0:Author::fullname()
Returns the author's name
CPAN:s0:Author::name()
An alias for fullname
CPAN:s0:Bundle::as_glimpse()
Returns a one-line description of the bundle
CPAN:s0:Bundle::as_string()
Returns a multi-line description of the bundle
CPAN:s0:Bundle::clean()
Recursively runs the "clean" method on all items con
tained in the bundle.
CPAN:s0:Bundle::contains()
Returns a list of objects' IDs contained in a bundle.
The associated objects may be bundles, modules or dis
tributions.
CPAN::Bundle::force($method,@args)
Forces CPAN to perform a task that normally would have
failed. Force takes as arguments a method name to be
called and any number of additional arguments that
should be passed to the called method. The internals
of the object get the needed changes so that CPAN.pm
does not refuse to take the action. The "force" is
passed recursively to all contained objects.
CPAN:s0:Bundle::get()
Recursively runs the "get" method on all items con
tained in the bundle
CPAN:s0:Bundle::inst_file()
Returns the highest installed version of the bundle in
either @INC or "$CPAN::Config-"{cpan_home}>. Note that
this is different from CPAN::Module::inst_file.
CPAN:s0:Bundle::inst_version()
Like CPAN::Bundle::inst_file, but returns the $VERSION
CPAN:s0:Bundle::uptodate()
Returns 1 if the bundle itself and all its members are
uptodate.
CPAN:s0:Bundle::install()
Recursively runs the "install" method on all items
contained in the bundle
CPAN:s0:Bundle::make()
Recursively runs the "make" method on all items con
tained in the bundle
CPAN:s0:Bundle::readme()
Recursively runs the "readme" method on all items con
tained in the bundle
CPAN:s0:Bundle::test()
Recursively runs the "test" method on all items con
tained in the bundle
CPAN:s0:Distribution::as_glimpse()
Returns a one-line description of the distribution
CPAN:s0:Distribution::as_string()
Returns a multi-line description of the distribution
CPAN:s0:Distribution::clean()
Changes to the directory where the distribution has
been unpacked and runs "make clean" there.
CPAN:s0:Distribution::containsmods()
Returns a list of IDs of modules contained in a dis
tribution file. Only works for distributions listed
in the 02packages.details.txt.gz file. This typically
means that only the most recent version of a distribu
tion is covered.
CPAN:s0:Distribution::cvs_import()
Changes to the directory where the distribution has
been unpacked and runs something like
cvs -d $cvs_root import -m $cvs_log $cvs_dir $userid v$version
there.
CPAN:s0:Distribution::dir()
Returns the directory into which this distribution has
been unpacked.
CPAN::Distribution::force($method,@args)
Forces CPAN to perform a task that normally would have
failed. Force takes as arguments a method name to be
called and any number of additional arguments that
should be passed to the called method. The internals
of the object get the needed changes so that CPAN.pm
does not refuse to take the action.
CPAN:s0:Distribution::get()
Downloads the distribution from CPAN and unpacks it.
Does nothing if the distribution has already been
downloaded and unpacked within the current session.
CPAN:s0:Distribution::install()
Changes to the directory where the distribution has
been unpacked and runs the external command "make
install" there. If "make" has not yet been run, it
will be run first. A "make test" will be issued in any
case and if this fails, the install will be cancelled.
The cancellation can be avoided by letting "force" run
the "install" for you.
CPAN:s0:Distribution::isa_perl()
Returns 1 if this distribution file seems to be a perl
distribution. Normally this is derived from the file
name only, but the index from CPAN can contain a hint
to achieve a return value of true for other filenames
too.
CPAN:s0:Distribution::look()
Changes to the directory where the distribution has
been unpacked and opens a subshell there. Exiting the
subshell returns.
CPAN:s0:Distribution::make()
First runs the "get" method to make sure the distribu
tion is downloaded and unpacked. Changes to the direc
tory where the distribution has been unpacked and runs
the external commands "perl Makefile.PL" and "make"
there.
CPAN:s0:Distribution::prereq_pm()
Returns the hash reference that has been announced by
a distribution as the PREREQ_PM hash in the Make
file.PL. Note: works only after an attempt has been
made to "make" the distribution. Returns undef other
wise.
CPAN:s0:Distribution::readme()
Downloads the README file associated with a distribu
tion and runs it through the pager specified in
"$CPAN::Config-"{pager}>.
CPAN:s0:Distribution::test()
Changes to the directory where the distribution has
been unpacked and runs "make test" there.
CPAN:s0:Distribution::uptodate()
Returns 1 if all the modules contained in the distri
bution are uptodate. Relies on containsmods.
CPAN:s0:Index::force_reload()
Forces a reload of all indices.
CPAN:s0:Index::reload()
Reloads all indices if they have been read more than
"$CPAN::Config-"{index_expire}> days.
CPAN:s0:InfoObj::dump()
CPAN::Author, CPAN::Bundle, CPAN::Module, and
CPAN::Distribution inherit this method. It prints the
data structure associated with an object. Useful for
debugging. Note: the data structure is considered
internal and thus subject to change without notice.
CPAN:s0:Module::as_glimpse()
Returns a one-line description of the module
CPAN:s0:Module::as_string()
Returns a multi-line description of the module
CPAN:s0:Module::clean()
Runs a clean on the distribution associated with this
module.
CPAN:s0:Module::cpan_file()
Returns the filename on CPAN that is associated with
the module.
CPAN:s0:Module::cpan_version()
Returns the latest version of this module available on
CPAN.
CPAN:s0:Module::cvs_import()
Runs a cvs_import on the distribution associated with
this module.
CPAN:s0:Module::description()
Returns a 44 chracter description of this module. Only
available for modules listed in The Module List
(CPAN/modules/00modlist.long.html or 00mod
list.long.txt.gz)
CPAN::Module::force($method,@args)
Forces CPAN to perform a task that normally would have
failed. Force takes as arguments a method name to be
called and any number of additional arguments that
should be passed to the called method. The internals
of the object get the needed changes so that CPAN.pm
does not refuse to take the action.
CPAN:s0:Module::get()
Runs a get on the distribution associated with this
module.
CPAN:s0:Module::inst_file()
Returns the filename of the module found in @INC. The
first file found is reported just like perl itself
stops searching @INC when it finds a module.
CPAN:s0:Module::inst_version()
Returns the version number of the module in readable
format.
CPAN:s0:Module::install()
Runs an "install" on the distribution associated with
this module.
CPAN:s0:Module::look()
Changes to the directory where the distribution
assoicated with this module has been unpacked and
opens a subshell there. Exiting the subshell returns.
CPAN:s0:Module::make()
Runs a "make" on the distribution associated with this
module.
CPAN:s0:Module::manpage_headline()
If module is installed, peeks into the module's man
page, reads the headline and returns it. Moreover, if
the module has been downloaded within this session,
does the equivalent on the downloaded module even if
it is not installed.
CPAN:s0:Module::readme()
Runs a "readme" on the distribution associated with
this module.
CPAN:s0:Module::test()
Runs a "test" on the distribution associated with this
module.
CPAN:s0:Module::uptodate()
Returns 1 if the module is installed and up-to-date.
CPAN:s0:Module::userid()
Returns the author's ID of the module.
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
locally by placing a conformant Bundle file somewhere into
your @INC path. The autobundle() command which is avail
able in the shell interface does that for you by including
all currently installed modules in a snapshot bundle file.
Prerequisites
If you have a local mirror of CPAN and can access all
files with "file:" URLs, then you only need a perl better
than perl5.003 to run this module. Otherwise Net::FTP is
strongly recommended. LWP may be required for non-UNIX
systems or if your nearest CPAN site is associated with an
URL that is not "ftp:".
If you have neither Net::FTP nor LWP, there is a fallback
mechanism implemented for an external ftp command or for
an external lynx command.
Finding packages and VERSION
This module presumes that all packages on CPAN
declare their $VERSION variable in an easy to parse man
ner. This prerequisite can hardly be relaxed because it
consumes far too much memory to load all packages into
the running program just to determine the $VERSION vari
able. Currently all programs that are dealing with ver
sion use something like this
perl -MExtUtils::MakeMaker -le \
'print MM->parse_version(shift)' filename
If you are author of a package and wonder if your $VER
SION can be parsed, please try the above method.
come as compressed or gzipped tarfiles or as zip files
and contain a Makefile.PL (well, we try to handle a bit
more, but without much enthusiasm).
Debugging
The debugging of this module is a bit complex, 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.
For code debugging in interactive mode you can try "o
debug" which will list options for debugging the various
parts of the code. You should know that "o debug" has
built-in completion support.
For data debugging there is the "dump" command which takes
the same arguments as make/test/install and outputs the
object's Data::Dumper dump.
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
cache_metadata use serializer to cache metadata
cpan_home local directory reserved for this package
dontload_hash anonymous hash: modules in the keys will not be
loaded by the CPAN::has_inst() routine
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')
proxy_user username for accessing an authenticating proxy
proxy_pass password for accessing an authenticating proxy
scan_cache controls scanning of cache ('atstart' or 'never')
tar location of external program tar
term_is_latin if true internal UTF-8 is translated to ISO-8859-1
(and nonsense for characters outside latin range)
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 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
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
Populating a freshly installed perl with my favorite mod
ules is pretty easy if you maintain a private bundle defi
nition file. To get a useful blueprint of a bundle defini
tion file, the command autobundle can be used on the CPAN
shell command line. This command writes a bundle defini
tion file for all modules that are installed for the cur
rently 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 keeping 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 untended.
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. For further informations on fire
walls, it is recommended to consult the documentation that
comes with the ncftp program. If you are unable to go
through the firewall with a simple Perl setup, it is very
likely that you can configure ncftp so that it works for
your firewall.
Three basic types of firewalls
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 needed as you can access hosts
directly.
Configuring lynx or ncftp for going through a firewall
If you can go through your firewall with e.g. lynx, pre
sumably with a command such as
/usr/local/bin/lynx -pscott:tiger
then you would configure CPAN.pm with the command
o conf lynx "/usr/local/bin/lynx -pscott:tiger"
That's all. Similarly for ncftp or ftp, you would config
ure something like
o conf ncftp "/usr/bin/ncftp -f /home/scott/ncftplogin.cfg"
Your milage may vary...
FAQ
1) I installed a new version of module X but CPAN keeps
saying, I have the old version installed
Most probably you do have the old version installed.
This can happen if a module installs itself into a
different directory in the @INC path than it was pre
viously installed. This is not really a CPAN.pm prob
lem, you would have the same problem when installing
the module manually. The easiest way to prevent this
behaviour is to add the argument "UNINST=1" to the
"make install" call, and that is why many people add
this argument permanently by configuring
o conf make_install_arg UNINST=1
2) So why is UNINST=1 not the default?
Because there are people who have their precise expec
tations about who may install where in the @INC path
and who uses which @INC array. In fine tuned environ
ments "UNINST=1" can cause damage.
3) I want to clean up my mess, and install a new perl
along with all modules I have. How do I go about it?
Run the autobundle command for your old perl and
optionally rename the resulting bundle file (e.g. Bun
dle/mybundle.pm), install the new perl with the Con
figure option prefix, e.g.
./Configure -Dprefix=/usr/local/perl-5.6.78.9
Install the bundle file you produced in the first step
with something like
cpan> install Bundle::mybundle
and you're done.
4) When I install bundles or multiple modules with one
command there is too much output to keep track of.
You may want to configure something like
o conf make_arg "| tee -ai /root/.cpan/logs/make.out"
o conf make_install_arg "| tee -ai /root/.cpan/logs/make_install.out"
so that STDOUT is captured in a file for later inspec
tion.
5) I am not root, how can I install a module in a per
sonal directory?
You will most probably like something like this:
o conf makepl_arg "LIB=~/myperl/lib \
INSTALLMAN1DIR=~/myperl/man/man1 \
INSTALLMAN3DIR=~/myperl/man/man3"
install Sybase::Sybperl
You can make this setting permanent like all "o conf"
settings with "o conf commit".
You will have to add ~/myperl/man to the MANPATH envi
ronment variable and also tell your perl programs to
look into ~/myperl/lib, e.g. by including
use lib "$ENV{HOME}/myperl/lib";
or setting the PERL5LIB environment variable.
Another thing you should bear in mind is that the
UNINST parameter should never be set if you are not
root.
6) How to get a package, unwrap it, and make a change
before building it?
look Sybase::Sybperl
7) I installed a Bundle and had a couple of fails. When I
retried, everything resolved nicely. Can this be fixed
to work on first try?
The reason for this is that CPAN does not know the
dependencies of all modules when it starts out. To
decide about the additional items to install, it just
uses data found in the generated Makefile. An unde
tected missing piece breaks the process. But it may
well be that your Bundle installs some prerequisite
later than some depending item and thus your second
try is able to resolve everything. Please note,
CPAN.pm does not know the dependency tree in advance
and cannot sort the queue of things to install in a
topologically correct order. It resolves perfectly
well IFF all modules declare the prerequisites cor
rectly with the PREREQ_PM attribute to MakeMaker. For
bundles which fail and you need to install often, it
is recommended sort the Bundle definition file manu
ally. It is planned to improve the metadata situation
for dependencies on CPAN in general, but this will
still take some time.
8) In our intranet we have many modules for internal use.
How can I integrate these modules with CPAN.pm but
without uploading the modules to CPAN?
Have a look at the CPAN::Site module.
9) When I run CPAN's shell, I get error msg about line 1
to 4, setting meta input/output via the /etc/inputrc
file.
Some versions of readline are picky about capitaliza
tion in the /etc/inputrc file and specifically RedHat
6.2 comes with a /etc/inputrc that contains the word
"on" in lowercase. Change the occurrences of "on" to
"On" and the bug should disappear.
10) Some authors have strange characters in their names.
Internally CPAN.pm uses the UTF-8 charset. If your
terminal is expecting ISO-8859-1 charset, a converter
can be activated by setting term_is_latin to a true
value in your config file. One way of doing so would
be
cpan> ! $CPAN::Config->{term_is_latin}=1
Extended support for converters will be made available
as soon as perl becomes stable with regard to charset
issues.
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/,
modules/ and scripts/. CPAN is PAUSE plus the clpa/, doc/,
misc/, ports/, and src/.
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>
TRANSLATIONS
Kawai,Takanori provides a Japanese translation of this
manpage at http://mem
ber.nifty.ne.jp/hippo2000/perltips/CPAN.htm
SEE ALSOperl(1), CPAN:\fIs0:Nox(3)2001-02-22 perl v5.6.1 CPAN(3)
