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CPAN - query, download and build perl modules from CPAN sites
Interactive mode:
perl -MCPAN -e shell
Basic commands:
# Modules:
cpan> install Acme::Meta # in the shell
CPAN::Shell->install("Acme::Meta"); # in perl
# Distributions:
cpan> install NWCLARK/Acme-Meta-0.02.tar.gz # in the shell
install("NWCLARK/Acme-Meta-0.02.tar.gz"); # in perl
# module objects:
$mo = CPAN::Shell->expandany($mod);
$mo = CPAN::Shell->expand("Module",$mod); # same thing
# distribution objects:
$do = CPAN::Shell->expand("Module",$mod)->distribution;
$do = CPAN::Shell->expandany($distro); # same thing
$do = CPAN::Shell->expand("Distribution",
$distro); # same thing
The CPAN module automates or at least simplifies the make and install of
perl modules and extensions. It includes some primitive searching
capabilities and knows how to use LWP, HTTP::Tiny, Net::FTP and certain
external download clients to fetch distributions from the net.
These are fetched from one or more mirrored CPAN (Comprehensive Perl
Archive Network) sites and unpacked in a dedicated directory.
The CPAN module also supports named and versioned *bundles* of modules.
Bundles simplify handling of sets of related modules. See Bundles below.
The package contains a session manager and a cache manager. The session
manager keeps track of what has been fetched, built, and installed in
the current session. The cache manager keeps track of the disk space
occupied by the make processes and deletes excess space using a simple
FIFO mechanism.
All methods provided are accessible in a programmer style and in an
interactive shell style.
CPAN::shell([$prompt, $command]) Starting Interactive Mode
Enter interactive mode by running
perl -MCPAN -e shell
which puts you into a readline interface. If "Term::ReadKey" and either
of "Term::ReadLine::Perl" or "Term::ReadLine::Gnu" are installed,
history and command completion are supported.
Once at the command line, type "h" for one-page help screen; the rest
should be self-explanatory.
The function call "shell" takes two optional arguments: one the prompt,
the second the default initial command line (the latter only works if a
real ReadLine interface 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 to these commands are either strings exactly matching the
identification string of an object, or regular expressions matched
case-insensitively against various attributes of the objects. The
parser only recognizes a regular expression when you enclose it with
The principle is that the number of objects found influences how an
item is displayed. If the search finds one item, the result is
displayed with the rather verbose method "as_string", but if more than
one is found, each object is displayed with the terse method
cpan> m Acme::MetaSyntactic
Module id = Acme::MetaSyntactic
CPAN_USERID BOOK (Philippe Bruhat (BooK) <[...]>)
CPAN_FILE B/BO/BOOK/Acme-MetaSyntactic-0.99.tar.gz
UPLOAD_DATE 2006-11-06
MANPAGE Acme::MetaSyntactic - Themed metasyntactic variables names
INST_FILE /usr/local/lib/perl/5.10.0/Acme/
cpan> a BOOK
Author id = BOOK
EMAIL [...]
FULLNAME Philippe Bruhat (BooK)
cpan> d BOOK/Acme-MetaSyntactic-0.99.tar.gz
Distribution id = B/BO/BOOK/Acme-MetaSyntactic-0.99.tar.gz
CPAN_USERID BOOK (Philippe Bruhat (BooK) <[...]>)
CONTAINSMODS Acme::MetaSyntactic Acme::MetaSyntactic::Alias [...]
UPLOAD_DATE 2006-11-06
cpan> m /lorem/
Module = Acme::MetaSyntactic::loremipsum (BOOK/Acme-MetaSyntactic-0.99.tar.gz)
Module Text::Lorem (ADEOLA/Text-Lorem-0.3.tar.gz)
Module Text::Lorem::More (RKRIMEN/Text-Lorem-More-0.12.tar.gz)
Module Text::Lorem::More::Source (RKRIMEN/Text-Lorem-More-0.12.tar.gz)
cpan> i /berlin/
Distribution BEATNIK/Filter-NumberLines-0.02.tar.gz
Module = DateTime::TimeZone::Europe::Berlin (DROLSKY/DateTime-TimeZone-0.7904.tar.gz)
Module Filter::NumberLines (BEATNIK/Filter-NumberLines-0.02.tar.gz)
Author [...]
The examples illustrate several aspects: the first three queries
target modules, authors, or distros directly and yield exactly one
result. The last two use regular expressions and yield several
results. The last one targets all of bundles, modules, authors, and
distros simultaneously. When more than one result is available, they
are printed in one-line format.
"get", "make", "test", "install", "clean" modules or distributions
These commands take any number of arguments and investigate what is
necessary to perform the action. Argument processing is as follows:
known module name in format Foo/ module
other embedded slash distribution
- with trailing slash dot directory
enclosing slashes regexp
known module name in format Foo::Bar module
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 META.yml or
Makefile.PL (this behavior is controlled by the configuration
parameter "prerequisites_policy"). If an argument is enclosed in
slashes it is treated as a regular expression: it is expanded and if
the result is a single object (distribution, bundle or module), this
object is processed.
install Dummy::Perl # installs the module
install AUXXX/Dummy-Perl-3.14.tar.gz # installs that distribution
install /Dummy-Perl-3.14/ # same if the regexp is unambiguous
"get" downloads a distribution file and untars or unzips it, "make"
builds it, "test" runs the test suite, and "install" installs it.
Any "make" or "test" is run unconditionally. An
install <distribution_file>
is also run unconditionally. But for
install <module>
CPAN checks whether an install is needed and prints *module up to
date* if the distribution file containing the module doesn't need
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 of whether
it succeeded or not. It does not repeat a test run if the test has
been run successfully before. Same for install runs.
The "force" pragma may precede another command (currently: "get",
"make", "test", or "install") to execute the command from scratch and
attempt to continue past certain errors. See the section below on the
"force" and the "fforce" pragma.
The "notest" pragma skips the test part in the build process.
cpan> notest install Tk
A "clean" command results in a
make clean
being executed within the distribution file's working directory.
"readme", "perldoc", "look" module or distribution
"readme" displays the README file of the associated distribution.
"Look" gets and untars (if not yet done) the distribution file,
changes to the appropriate directory and opens a subshell process in
that directory. "perldoc" displays the module's pod documentation in
html or plain text format.
"ls" author
"ls" globbing_expression
The first form lists all distribution files in and below an author's
CPAN directory as stored in the CHECKSUMS files distributed on CPAN.
The listing recurses into subdirectories.
The second form limits or expands the output with shell globbing as in
the following examples:
ls JV/make*
ls GSAR/*make*
ls */*make*
The last example is very slow and outputs extra progress indicators
that break the alignment of the result.
Note that globbing only lists directories explicitly asked for, for
example FOO/* will not list FOO/bar/Acme-Sthg-n.nn.tar.gz. This may be
regarded as a bug that may be changed in some future version.
The "failed" command reports all distributions that failed on one of
"make", "test" or "install" for some reason in the currently running
shell session.
Persistence between sessions
If the "YAML" or the "YAML::Syck" module is installed a record of the
internal state of all modules is written to disk after each step. The
files contain a signature of the currently running perl version for
later perusal.
If the configurations variable "build_dir_reuse" is set to a true
value, then reads the collected YAML files. If the stored
signature matches the currently running perl, the stored state is
loaded into memory such that persistence between sessions is
effectively established.
The "force" and the "fforce" pragma
To speed things up in complex installation scenarios, keeps
track of what it has already done and refuses to do some things a
second time. A "get", a "make", and an "install" are not repeated. A
"test" is repeated only if the previous test was unsuccessful. The
diagnostic message when refuses to do something a second time
is one of *Has already been *"unwrapped|made|tested successfully" or
something similar. Another situation where CPAN refuses to act is an
"install" if the corresponding "test" was not successful.
In all these cases, the user can override this stubborn behaviour by
prepending the command with the word force, for example:
cpan> force get Foo
cpan> force make AUTHOR/Bar-3.14.tar.gz
cpan> force test Baz
cpan> force install Acme::Meta
Each *forced* command is executed with the corresponding part of its
memory erased.
The "fforce" pragma is a variant that emulates a "force get" which
erases the entire memory followed by the action specified, effectively
restarting the whole get/make/test/install procedure from scratch.
Interactive sessions maintain a lockfile, by default "~/.cpan/.lock".
Batch jobs can run without a lockfile and not disturb each other.
The shell offers to run in *downgraded mode* when another process is
holding the lockfile. This is an experimental feature that is not yet
tested very well. This second shell then does not write the history
file, does not use the metadata file, and has a different prompt.
Signals 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. ignores SIGPIPE. If the user sets "inactivity_timeout", a
SIGALRM is used during the run of the "perl Makefile.PL" or "perl
Build.PL" subprocess. A SIGALRM is also used during module version
parsing, and is controlled by "version_timeout".
The commands available in the shell interface are methods in the package
CPAN::Shell. If you enter the shell command, your input is split by the
Text::ParseWords::shellwords() routine, which acts like most shells do.
The first word is interpreted as the method to be invoked, and the rest
of the words are treated as the method's arguments. Continuation lines
are supported by ending a line with a literal backslash.
"autobundle" writes a bundle file into the
"$CPAN::Config->{cpan_home}/Bundle" directory. The file contains a list
of all modules that are both available from CPAN and currently installed
within @INC. Duplicates of each distribution are suppressed. The name of
the bundle file is based on the current date and a counter, e.g.
Bundle/ This is installed again by running
"cpan Bundle::Snapshot_2012_05_21_00", or installing
"Bundle::Snapshot_2012_05_21_00" from the CPAN shell.
Return value: path to the written file.
Note: this feature is still in alpha state and may change in future
versions of
This commands provides a statistical overview over recent download
activities. The data for this is collected in the YAML file
"FTPstats.yml" in your "cpan_home" directory. If no YAML module is
configured or YAML not installed, no stats are provided.
Install all distributions that have been tested successfully but
have not yet been installed. See also "is_tested".
List all build directories of distributions that have been tested
successfully but have not yet been installed. See also
mkmyconfig() writes your own CPAN::MyConfig file into your "~/.cpan/"
directory so that you can save your own preferences instead of the
system-wide ones.
r [Module|/Regexp/]...
scans current perl installation for modules that have a newer version
available on CPAN and provides a list of them. If called without
argument, all potential upgrades are listed; if called with arguments
the list is filtered to the modules and regexps given as arguments.
The listing looks something like this:
Package namespace installed latest in CPAN file
CPAN 1.94_64 1.9600 ANDK/CPAN-1.9600.tar.gz
CPAN::Reporter 1.1801 1.1902 DAGOLDEN/CPAN-Reporter-1.1902.tar.gz
YAML 0.70 0.73 INGY/YAML-0.73.tar.gz
YAML::Syck 1.14 1.17 AVAR/YAML-Syck-1.17.tar.gz
YAML::Tiny 1.44 1.50 ADAMK/YAML-Tiny-1.50.tar.gz
CGI 3.43 3.55 MARKSTOS/
Module::Build::YAML 1.40 1.41 DAGOLDEN/Module-Build-0.3800.tar.gz
TAP::Parser::Result::YAML 3.22 3.23 ANDYA/Test-Harness-3.23.tar.gz
YAML::XS 0.34 0.35 INGY/YAML-LibYAML-0.35.tar.gz
It suppresses duplicates in the column "in CPAN file" such that
distributions with many upgradeable modules are listed only once.
Note that the list is not sorted.
The "recent" command downloads a list of recent uploads to CPAN and
displays them *slowly*. While the command is running, a $SIG{INT} exits
the loop after displaying the current item.
Note: This command requires XML::LibXML installed.
Note: This whole command currently is just a hack and will probably
change in future versions of, but the general approach will
likely remain.
Note: See also smoke
recompile() is a special command that takes no argument and runs the
make/test/install cycle with brute force over all installed dynamically
loadable extensions (a.k.a. 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 should try the CPAN::Nox module for recovery.
report Bundle|Distribution|Module
The "report" command temporarily turns on the "test_report" config
variable, then runs the "force test" command with the given arguments.
The "force" pragma reruns the tests and repeats every step that might
have failed before.
*** WARNING: this command downloads and executes software from CPAN to
your computer of completely unknown status. You should never do this
with your normal account and better have a dedicated well separated and
secured machine to do this. ***
The "smoke" command takes the list of recent uploads to CPAN as provided
by the "recent" command and tests them all. While the command is running
$SIG{INT} is defined to mean that the current item shall be skipped.
Note: This whole command currently is just a hack and will probably
change in future versions of, but the general approach will
likely remain.
Note: See also recent
upgrade [Module|/Regexp/]...
The "upgrade" command first runs an "r" command with the given arguments
and then installs the newest versions of all modules that were listed by
The four "CPAN::*" Classes: Author, Bundle, Module, Distribution
Although it may be considered internal, the class hierarchy does matter
for both users and programmer. deals with the four classes
mentioned above, and those classes all share a set of methods. 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
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 underscore into the
module version number which will also be reflected in the distribution
name when you run 'make dist'), so the really hottest and newest
distribution is not always the default. If a module Foo circulates on
CPAN in both version 1.23 and 1.23_90, 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.
Integrating local directories
Note: this feature is still in alpha state and may change in future
versions of
Distribution objects are normally distributions from the CPAN, but there
is a slightly degenerate case for Distribution objects, too, of projects
held on the local disk. These distribution objects have the same name as
the local directory and end with a dot. A dot by itself is also allowed
for the current directory at the time was used. All actions such
as "make", "test", and "install" are applied directly to that directory.
This gives the command "cpan ." an interesting touch: while the normal
mantra of installing a CPAN module without is one of
perl Makefile.PL perl Build.PL
( go and get prerequisites )
make ./Build
make test ./Build test
make install ./Build install
the command "cpan ." does all of this at once. It figures out which of
the two mantras is appropriate, fetches and installs all prerequisites,
takes care of them recursively, and finally finishes the installation of
the module in the current directory, be it a CPAN module or not.
The typical usage case is for private modules or working copies of
projects from remote repositories on the local disk.
The usual shell redirection symbols " | " and ">" are recognized by the
cpan shell only when surrounded by whitespace. So piping to pager or
redirecting output into a file works somewhat as in a normal shell, with
the stipulation that you must type extra spaces.
Plugin support ***EXPERIMENTAL***
Plugins are objects that implement any of currently eight methods:
The "plugin_list" configuration parameter holds a list of strings of the
At run time, each listed plugin is instantiated as a singleton object by
running the equivalent of this pseudo code:
my $plugin = <string representation from config>;
<generate Modulename and arguments from $plugin>;
my $p = $instance{$plugin} ||= Modulename->new($arg0,$arg1,...);
The generated singletons are kept around from instantiation until the
end of the shell session. <plugin_list> can be reconfigured at any time
at run time. While the cpan shell is running, it checks all activated
plugins at each of the 8 reference points listed above and runs the
respective method if it is implemented for that object. The method is
called with the active CPAN::Distribution object passed in as an
When the CPAN module is used for the first time, a configuration
dialogue tries to determine a couple of site specific options. The
result of the dialog is stored in a hash reference $CPAN::Config in a
file CPAN/
Default values defined in the CPAN/ file can be overridden in a
user specific file: CPAN/ Such a file is best placed in
"$HOME/.cpan/CPAN/", because "$HOME/.cpan" is added to the
search path of the CPAN module before the use() or require() statements.
The mkmyconfig command writes this file for you.
The "o conf" command has various bells and whistles:
completion support
If you have a ReadLine module installed, you can hit TAB at any
point of the commandline and "o conf" will offer you completion for
the built-in subcommands and/or config variable names.
displaying some help: o conf help
Displays a short help
displaying current values: o conf [KEY]
Displays the current value(s) for this config variable. Without KEY,
displays all subcommands and config variables.
o conf shell
If KEY starts and ends with a slash, the string in between is
treated as a regular expression and only keys matching this regexp
are displayed
o conf /color/
changing of scalar values: o conf KEY VALUE
Sets the config variable KEY to VALUE. The empty string can be
specified as usual in shells, with '' or ""
o conf wget /usr/bin/wget
changing of list values: o conf KEY SHIFT|UNSHIFT|PUSH|POP|SPLICE|LIST
If a config variable name ends with "list", it is a list. "o conf
KEY shift" removes the first element of the list, "o conf KEY pop"
removes the last element of the list. "o conf KEYS unshift LIST"
prepends a list of values to the list, "o conf KEYS push LIST"
appends a list of valued to the list.
Likewise, "o conf KEY splice LIST" passes the LIST to the
corresponding splice command.
Finally, any other list of arguments is taken as a new list value
for the KEY variable discarding the previous value.
o conf urllist unshift
o conf urllist splice 3 1
o conf urllist http://cpan1.local http://cpan2.local
reverting to saved: o conf defaults
Reverts all config variables to the state in the saved config file.
saving the config: o conf commit
Saves all config variables to the current config file
(CPAN/ or CPAN/ that was loaded at start).
The configuration dialog can be started any time later again by issuing
the command " o conf init " in the CPAN shell. A subset of the
configuration dialog can be run by issuing "o conf init WORD" where WORD
is any valid config variable or a regular expression.
Config Variables
The following keys in the hash reference $CPAN::Config are currently
applypatch path to external prg
auto_commit commit all changes to config variables to disk
build_cache size of cache for directories to build modules
build_dir locally accessible directory to build modules
build_dir_reuse boolean if distros in build_dir are persistent
to install or not to install when a module is
only needed for building. yes|no|ask/yes|ask/no
bzip2 path to external prg
cache_metadata use serializer to cache metadata
check_sigs if signatures should be verified
remove build directory immediately after a
successful install
colorize_debug Term::ANSIColor attributes for debugging output
colorize_output boolean if Term::ANSIColor should colorize output
colorize_print Term::ANSIColor attributes for normal output
colorize_warn Term::ANSIColor attributes for warnings
boolean if you want to see current command number
commands_quote preferred character to use for quoting external
commands when running them. Defaults to double
quote on Windows, single tick everywhere else;
can be set to space to disable quoting
whether to ask if opening a connection is ok before
urllist is specified
cpan_home local directory reserved for this package
curl path to external prg
dontload_hash DEPRECATED
dontload_list arrayref: modules in the list will not be
loaded by the CPAN::has_inst() routine
ftp path to external prg
ftp_passive if set, the environment variable FTP_PASSIVE is set
for downloads
ftp_proxy proxy host for ftp requests
ftpstats_period max number of days to keep download statistics
ftpstats_size max number of items to keep in the download statistics
getcwd see below
gpg path to external prg
gzip location of external program gzip
halt_on_failure stop processing after the first failure of queued
items or dependencies
histfile file to maintain history between sessions
histsize maximum number of lines to keep in histfile
http_proxy proxy host for http requests
inactivity_timeout breaks interactive Makefile.PLs or Build.PLs
after this many seconds inactivity. Set to 0 to
disable timeouts.
index_expire refetch index files after this many days
if true, suppress the startup message
keep_source_where directory in which to keep the source (if we do)
report loading of optional modules used by
lynx path to external prg
make location of external make program
make_arg arguments that should always be passed to 'make'
the make command for running 'make install', for
example 'sudo make'
make_install_arg same as make_arg for 'make install'
makepl_arg arguments passed to 'perl Makefile.PL'
mbuild_arg arguments passed to './Build'
mbuild_install_arg arguments passed to './Build install'
command to use instead of './Build' when we are
in the install stage, for example 'sudo ./Build'
mbuildpl_arg arguments passed to 'perl Build.PL'
ncftp path to external prg
ncftpget path to external prg
no_proxy don't proxy to these hosts/domains (comma separated list)
pager location of external program more (or any pager)
password your password if you CPAN server wants one
patch path to external prg
patches_dir local directory containing patch files
perl5lib_verbosity verbosity level for PERL5LIB additions
plugin_list list of active hooks (see Plugin support above
and the CPAN::Plugin module)
per default all untar operations are done with
Archive::Tar; by setting this variable to true
the external tar command is used if available
prefer_installer legal values are MB and EUMM: if a module comes
with both a Makefile.PL and a Build.PL, use the
former (EUMM) or the latter (MB); if the module
comes with only one of the two, that one will be
used no matter the setting
what to do if you are missing module prerequisites
('follow' automatically, 'ask' me, or 'ignore')
For 'follow', also sets PERL_AUTOINSTALL and
PERL_EXTUTILS_AUTOINSTALL for "--defaultdeps" if
not already set
prefs_dir local directory to store per-distro build options
proxy_user username for accessing an authenticating proxy
proxy_pass password for accessing an authenticating proxy
randomize_urllist add some randomness to the sequence of the urllist
recommends_policy whether recommended prerequisites should be included
scan_cache controls scanning of cache ('atstart', 'atexit' or 'never')
shell your favorite shell
boolean if r command tells which modules are versionless
show_upload_date boolean if commands should try to determine upload date
show_zero_versions boolean if r command tells for which modules $version==0
suggests_policy whether suggested prerequisites should be included
tar location of external program tar
tar_verbosity verbosity level for the tar command
term_is_latin deprecated: if true Unicode is translated to ISO-8859-1
(and nonsense for characters outside latin range)
term_ornaments boolean to turn ReadLine ornamenting on/off
test_report email test reports (if CPAN::Reporter is installed)
skip testing when previously tested ok (according to
CPAN::Reporter history)
unzip location of external program unzip
urllist arrayref to nearby CPAN sites (or equivalent locations)
use_prompt_default set PERL_MM_USE_DEFAULT for configure/make/test/install
use_sqlite use CPAN::SQLite for metadata storage (fast and lean)
username your username if you CPAN server wants one
version_timeout stops version parsing after this many seconds.
Default is 15 secs. Set to 0 to disable.
wait_list arrayref to a wait server to try (See CPAN::WAIT)
wget path to external prg
yaml_load_code enable YAML code deserialisation via CPAN::DeferredCode
yaml_module which module to use to read/write YAML files
You can set and query each of these options interactively in the cpan
shell with the "o conf" or the "o conf init" command as specified below.
"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
"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.
interactive editing: o conf init [MATCH|LIST]
Runs an interactive configuration dialog for matching variables.
Without argument runs the dialog over all supported config variables.
To specify a MATCH the argument must be enclosed by slashes.
o conf init ftp_passive ftp_proxy
o conf init /color/
Note: this method of setting config variables often provides more
explanation about the functioning of a variable than the manpage.
CPAN::anycwd($path): Note on config variable getcwd changes the current working directory often and needs to
determine its own current working directory. By default it uses
Cwd::cwd, but if for some reason this doesn't work on your system,
configure alternatives according to the following table:
cwd Calls Cwd::cwd
Calls Cwd::getcwd
Calls Cwd::fastcwd
Calls Cwd::getdcwd
Calls the external command cwd.
Note on the format of the urllist parameter
urllist parameters are URLs according to RFC 1738. We do a little
guessing if your URL is not compliant, but if you have problems with
"file" URLs, please try the correct format. Either:
The urllist parameter has CD-ROM support
The "urllist" parameter of the configuration table contains a list of
URLs used for downloading. If the list contains any "file" URLs, CPAN
always tries 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 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 to
see whether 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.
Maintaining the urllist parameter
If you have (or some other YAML module configured in
"yaml_module") installed, collects a few statistical data about
recent downloads. You can view the statistics with the "hosts" command
or inspect them directly by looking into the "FTPstats.yml" file in your
"cpan_home" directory.
To get some interesting statistics, it is recommended that
"randomize_urllist" be set; this introduces some amount of randomness
into the URL selection.
The "requires" and "build_requires" dependency declarations
Since version 1.88_51 modules declared as "build_requires" by a
distribution are treated differently depending on the config variable
"build_requires_install_policy". By setting
"build_requires_install_policy" to "no", such a module is not installed.
It is only built and tested, and then kept in the list of tested but
uninstalled modules. As such, it is available during the build of the
dependent module by integrating the path to the "blib/arch" and
"blib/lib" directories in the environment variable PERL5LIB. If
"build_requires_install_policy" is set ti "yes", then both modules
declared as "requires" and those declared as "build_requires" are
treated alike. By setting to "ask/yes" or "ask/no", asks the
user and sets the default accordingly.
Configuration for individual distributions (*Distroprefs*)
(Note: This feature has been introduced in 1.8854)
Distributions on CPAN usually behave according to what we call the CPAN
mantra. Or since the advent of Module::Build we should talk about two
perl Makefile.PL perl Build.PL
make ./Build
make test ./Build test
make install ./Build install
But some modules cannot be built with this mantra. They try to get some
extra data from the user via the environment, extra arguments, or
interactively--thus disturbing the installation of large bundles like
Phalanx100 or modules with many dependencies like Plagger.
The distroprefs system of "" addresses this problem by allowing
the user to specify extra informations and recipes in YAML files to
* pass additional arguments to one of the four commands,
* set environment variables
* instantiate an Expect object that reads from the console, waits for
some regular expressions and enters some answers
* temporarily override assorted "" configuration variables
* specify dependencies the original maintainer forgot
* disable the installation of an object altogether
See the YAML and Data::Dumper files that come with the ""
distribution in the "distroprefs/" directory for examples.
The YAML files themselves must have the ".yml" extension; all other
files are ignored (for two exceptions see *Fallback Data::Dumper and
Storable* below). The containing directory can be specified in ""
in the "prefs_dir" config variable. Try "o conf init prefs_dir" in the
CPAN shell to set and activate the distroprefs system.
Every YAML file may contain arbitrary documents according to the YAML
specification, and every document is treated as an entity that can
specify the treatment of a single distribution.
Filenames can be picked arbitrarily; "" always reads all files
(in alphabetical order) and takes the key "match" (see below in
*Language Specs*) as a hashref containing match criteria that determine
if the current distribution matches the YAML document or not.
Fallback Data::Dumper and Storable
If neither your configured "yaml_module" nor is installed, falls back to using Data::Dumper and Storable and looks for
files with the extensions ".dd" or ".st" in the "prefs_dir" directory.
These files are expected to contain one or more hashrefs. For
Data::Dumper generated files, this is expected to be done with by
defining $VAR1, $VAR2, etc. The YAML shell would produce these with the
ysh < somefile.yml > somefile.dd
For Storable files the rule is that they must be constructed such that
"Storable::retrieve(file)" returns an array reference and the array
elements represent one distropref object each. The conversion from YAML
would look like so:
perl -MYAML=LoadFile -MStorable=nstore -e '
nstore(\@y, shift)' somefile.yml
In bootstrapping situations it is usually sufficient to translate only a
few YAML files to Data::Dumper for crucial modules like "YAML::Syck",
"" and "". If you prefer Storable over Data::Dumper,
remember to pull out a Storable version that writes an older format than
all the other Storable versions that will need to read them.
The following example contains all supported keywords and structures
with the exception of "eexpect" which can be used instead of "expect".
comment: "Demo"
module: "Dancing::Queen"
distribution: "^CHACHACHA/Dancing-"
not_distribution: "\.zip$"
perl: "/usr/local/cariba-perl/bin/perl"
archname: "freebsd"
not_cc: "gcc"
disabled: 1
make: gmake
- "--somearg=specialcase"
env: {}
- "Which is your favorite fruit"
- "apple\n"
- all
- extra-all
env: {}
expect: []
commandline: "echo SKIPPING make"
args: []
env: {}
expect: []
args: []
- "Do you really want to install"
- "y\n"
- "ABCDE/Fedcba-3.14-ABCDE-01.patch"
LWP: 5.8
Test::Exception: 0.25
Spiffy: 0.30
Language Specs
Every YAML document represents a single hash reference. The valid keys
in this hash are as follows:
comment [scalar]
A comment
cpanconfig [hash]
Temporarily override assorted "" configuration variables.
Supported are: "build_requires_install_policy", "check_sigs",
"make", "make_install_make_command", "prefer_installer",
"test_report". Please report as a bug when you need another one
depends [hash] *** EXPERIMENTAL FEATURE ***
All three types, namely "configure_requires", "build_requires", and
"requires" are supported in the way specified in the META.yml
specification. The current implementation *merges* the specified
dependencies with those declared by the package maintainer. In a
future implementation this may be changed to override the original
disabled [boolean]
Specifies that this distribution shall not be processed at all.
features [array] *** EXPERIMENTAL FEATURE ***
Experimental implementation to deal with optional_features from
META.yml. Still needs coordination with installer software and
currently works only for META.yml declaring "dynamic_config=0". Use
with caution.
goto [string]
The canonical name of a delegate distribution to install instead.
Useful when a new version, although it tests OK itself, breaks
something else or a developer release or a fork is already uploaded
that is better than the last released version.
install [hash]
Processing instructions for the "make install" or "./Build install"
phase of the CPAN mantra. See below under *Processing Instructions*.
make [hash]
Processing instructions for the "make" or "./Build" phase of the
CPAN mantra. See below under *Processing Instructions*.
match [hash]
A hashref with one or more of the keys "distribution", "module",
"perl", "perlconfig", and "env" that specify whether a document is
targeted at a specific CPAN distribution or installation. Keys
prefixed with "not_" negates the corresponding match.
The corresponding values are interpreted as regular expressions. The
"distribution" related one will be matched against the canonical
distribution name, e.g. "AUTHOR/Foo-Bar-3.14.tar.gz".
The "module" related one will be matched against *all* modules
contained in the distribution until one module matches.
The "perl" related one will be matched against $^X (but with the
absolute path).
The value associated with "perlconfig" is itself a hashref that is
matched against corresponding values in the %Config::Config hash
living in the "" module. Keys prefixed with "not_" negates
the corresponding match.
The value associated with "env" is itself a hashref that is matched
against corresponding values in the %ENV hash. Keys prefixed with
"not_" negates the corresponding match.
If more than one restriction of "module", "distribution", etc. is
specified, the results of the separately computed match values must
all match. If so, the hashref represented by the YAML document is
returned as the preference structure for the current distribution.
patches [array]
An array of patches on CPAN or on the local disk to be applied in
order via an external patch program. If the value for the "-p"
parameter is 0 or 1 is determined by reading the patch beforehand.
The path to each patch is either an absolute path on the local
filesystem or relative to a patch directory specified in the
"patches_dir" configuration variable or in the format of a canonical
distro name. For examples please consult the distroprefs/ directory
in the distribution (these examples are not installed by
Note: if the "applypatch" program is installed and "CPAN::Config"
knows about it and a patch is written by the "makepatch" program,
then "" lets "applypatch" apply the patch. Both "makepatch"
and "applypatch" are available from CPAN in the "JV/makepatch-*"
pl [hash]
Processing instructions for the "perl Makefile.PL" or "perl
Build.PL" phase of the CPAN mantra. See below under *Processing
test [hash]
Processing instructions for the "make test" or "./Build test" phase
of the CPAN mantra. See below under *Processing Instructions*.
Processing Instructions
args [array]
Arguments to be added to the command line
A full commandline to run via "system()". During execution, the
environment variable PERL is set to $^X (but with an absolute path).
If "commandline" is specified, "args" is not used.
eexpect [hash]
Extended "expect". This is a hash reference with four allowed keys,
"mode", "timeout", "reuse", and "talk".
You must install the "Expect" module to use "eexpect". does
not install it for you.
"mode" may have the values "deterministic" for the case where all
questions come in the order written down and "anyorder" for the case
where the questions may come in any order. The default mode is
"timeout" denotes a timeout in seconds. Floating-point timeouts are
OK. With "mode=deterministic", the timeout denotes the timeout per
question; with "mode=anyorder" it denotes the timeout per byte
received from the stream or questions.
"talk" is a reference to an array that contains alternating
questions and answers. Questions are regular expressions and answers
are literal strings. The Expect module watches the stream from the
execution of the external program ("perl Makefile.PL", "perl
Build.PL", "make", etc.).
For "mode=deterministic", the injects the corresponding
answer as soon as the stream matches the regular expression.
For "mode=anyorder" answers a question as soon as the
timeout is reached for the next byte in the input stream. In this
mode you can use the "reuse" parameter to decide what will happen
with a question-answer pair after it has been used. In the default
case (reuse=0) it is removed from the array, avoiding being used
again accidentally. If you want to answer the question "Do you
really want to do that" several times, then it must be included in
the array at least as often as you want this answer to be given.
Setting the parameter "reuse" to 1 makes this repetition
env [hash]
Environment variables to be set during the command
expect [array]
You must install the "Expect" module to use "expect". does
not install it for you.
"expect: <array>" is a short notation for this "eexpect":
mode: deterministic
timeout: 15
talk: <array>
Schema verification with "Kwalify"
If you have the "Kwalify" module installed (which is part of the
Bundle::CPANxxl), then all your distroprefs files are checked for
syntactic correctness.
Example Distroprefs Files
"" comes with a collection of example YAML files. Note that these
are really just examples and should not be used without care because
they cannot fit everybody's purpose. After all, the authors of the
packages that ask questions had a need to ask, so you should watch their
questions and adjust the examples to your environment and your needs.
You have been warned:-)
If you do not enter the shell, shell commands are available both as
methods ("CPAN::Shell->install(...)") and as functions in the calling
package ("install(...)"). Before calling low-level commands, it makes
sense to initialize components of CPAN you need, e.g.:
High-level commands do such initializations automatically.
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. The arguments on the commandline are
passed as arguments to the method.
So if you take for example the shell command
notest install A B C
the actually executed command is
Each of the commands that produce listings of modules ("r",
"autobundle", "u") also return a list of the IDs of all modules within
the list.
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 returns only the first element of the list.
Like expand, but returns objects of the appropriate type, i.e.
CPAN::Bundle objects for bundles, CPAN::Module objects for modules,
and CPAN::Distribution objects for distributions. Note: it does not
expand to CPAN::Author objects.
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 Digest::SHA Data::Dumper)) {
# 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 schedule a *cron* job to watch 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 any output should all modules be up to date, 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.
If you prefer to do it more in a programmerish style in one single
process, something like this may better suit you:
# 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 too much output every day, you may want to watch only
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
# watch only for a new mod_perl module
$mod = CPAN::Shell->expand("Module","mod_perl");
exit if $mod->uptodate;
# new mod_perl arrived, let me know all update recommendations
Methods in the other Classes
Returns a one-line description of the author
Returns a multi-line description of the author
Returns the author's email address
Returns the author's name
An alias for fullname
Returns a one-line description of the bundle
Returns a multi-line description of the bundle
Recursively runs the "clean" method on all items contained in the
Returns a list of objects' IDs contained in a bundle. The associated
objects may be bundles, modules or distributions.
Forces CPAN to perform a task that it normally would have refused to
do. Force takes as arguments a method name to be called and any
number of additional arguments that should be passed to the called
method. The internals of the object get the needed changes so that does not refuse to take the action. The "force" is passed
recursively to all contained objects. See also the section above on
the "force" and the "fforce" pragma.
Recursively runs the "get" method on all items contained in the
Returns the highest installed version of the bundle in either @INC
or "$CPAN::Config->{cpan_home}". Note that this is different from
Like CPAN::Bundle::inst_file, but returns the $VERSION
Returns 1 if the bundle itself and all its members are up-to-date.
Recursively runs the "install" method on all items contained in the
Recursively runs the "make" method on all items contained in the
Recursively runs the "readme" method on all items contained in the
Recursively runs the "test" method on all items contained in the
Returns a one-line description of the distribution
Returns a multi-line description of the distribution
Returns the CPAN::Author object of the maintainer who uploaded this
Returns a string of the form "AUTHORID/TARBALL", where AUTHORID is
the author's PAUSE ID and TARBALL is the distribution filename.
Returns the distribution filename without any archive suffix. E.g
Changes to the directory where the distribution has been unpacked
and runs "make clean" there.
Returns a list of IDs of modules contained in a distribution file.
Works only for distributions listed in the 02packages.details.txt.gz
file. This typically means that just most recent version of a
distribution is covered.
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
Returns the directory into which this distribution has been
Forces CPAN to perform a task that it normally would have refused to
do. 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 does not refuse to take the action. See also the section
above on the "force" and the "fforce" pragma.
Downloads the distribution from CPAN and unpacks it. Does nothing if
the distribution has already been downloaded and unpacked within the
current session.
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" is issued in
any case and if this fails, the install is cancelled. The
cancellation can be avoided by letting "force" run the "install" for
This install method only has the power to install the distribution
if there are no dependencies in the way. To install an object along
with all its dependencies, use CPAN::Shell->install.
Note that install() gives no meaningful return value. See
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.
Changes to the directory where the distribution has been unpacked
and opens a subshell there. Exiting the subshell returns.
First runs the "get" method to make sure the distribution is
downloaded and unpacked. Changes to the directory where the
distribution has been unpacked and runs the external commands "perl
Makefile.PL" or "perl Build.PL" and "make" there.
Downloads the pod documentation of the file associated with a
distribution (in HTML format) and runs it through the external
command *lynx* specified in "$CPAN::Config->{lynx}". If *lynx* isn't
available, it converts it to plain text with the external command
*html2text* and runs it through the pager specified in
Returns the hash reference from the first matching YAML file that
the user has deposited in the "prefs_dir/" directory. The first
succeeding match wins. The files in the "prefs_dir/" are processed
alphabetically, and the canonical distro name (e.g.
AUTHOR/Foo-Bar-3.14.tar.gz) is matched against the regular
expressions stored in the $root->{match}{distribution} attribute
value. Additionally all module names contained in a distribution are
matched against the regular expressions in the
$root->{match}{module} attribute value. The two match values are
ANDed together. Each of the two attributes are optional.
Returns the hash reference that has been announced by a distribution
as the "requires" and "build_requires" elements. These can be
declared either by the "META.yml" (if authoritative) or can be
deposited after the run of "Build.PL" in the file "./_build/prereqs"
or after the run of "Makfile.PL" written as the "PREREQ_PM" hash in
a comment in the produced "Makefile". *Note*: this method only works
after an attempt has been made to "make" the distribution. Returns
undef otherwise.
Downloads the README file associated with a distribution and runs it
through the pager specified in "$CPAN::Config->{pager}".
Downloads report data for this distribution from
and displays a subset of them.
Returns the content of the META.yml of this distro as a hashref.
Note: works only after an attempt has been made to "make" the
distribution. Returns undef otherwise. Also returns undef if the
content of META.yml is not authoritative. (The rules about what
exactly makes the content authoritative are still in flux.)
Changes to the directory where the distribution has been unpacked
and runs "make test" there.
Returns 1 if all the modules contained in the distribution are
up-to-date. Relies on containsmods.
Forces a reload of all indices.
Reloads all indices if they have not been read for more than
"$CPAN::Config->{index_expire}" days.
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.
Returns a one-line description of the module in four columns: The
first column contains the word "Module", the second column consists
of one character: an equals sign if this module is already installed
and up-to-date, a less-than sign if this module is installed but can
be upgraded, and a space if the module is not installed. The third
column is the name of the module and the fourth column gives
maintainer or distribution information.
Returns a multi-line description of the module
Runs a clean on the distribution associated with this module.
Returns the filename on CPAN that is associated with the module.
Returns the latest version of this module available on CPAN.
Runs a cvs_import on the distribution associated with this module.
Returns a 44 character description of this module. Only available
for modules listed in The Module List
(CPAN/modules/00modlist.long.html or 00modlist.long.txt.gz)
Returns the CPAN::Distribution object that contains the current
version of this module.
Returns a hash reference. The keys of the hash are the letters "D",
"S", "L", "I", and <P>, for development status, support level,
language, interface and public licence respectively. The data for
the DSLIP status are collected by when authors
register their namespaces. The values of the 5 hash elements are
one-character words whose meaning is described in the table below.
There are also 5 hash elements "DV", "SV", "LV", "IV", and <PV> that
carry a more verbose value of the 5 status variables.
Where the 'DSLIP' characters have the following meanings:
D - Development Stage (Note: *NO IMPLIED TIMESCALES*):
i - Idea, listed to gain consensus or as a placeholder
c - under construction but pre-alpha (not yet released)
a/b - Alpha/Beta testing
R - Released
M - Mature (no rigorous definition)
S - Standard, supplied with Perl 5
S - Support Level:
m - Mailing-list
d - Developer
u - Usenet newsgroup comp.lang.perl.modules
n - None known, try comp.lang.perl.modules
a - abandoned; volunteers welcome to take over maintenance
L - Language Used:
p - Perl-only, no compiler needed, should be platform independent
c - C and perl, a C compiler will be needed
h - Hybrid, written in perl with optional C code, no compiler needed
+ - C++ and perl, a C++ compiler will be needed
o - perl and another language other than C or C++
I - Interface Style
f - plain Functions, no references used
h - hybrid, object and function interfaces available
n - no interface at all (huh?)
r - some use of unblessed References or ties
O - Object oriented using blessed references and/or inheritance
P - Public License
p - Standard-Perl: user may choose between GPL and Artistic
g - GPL: GNU General Public License
l - LGPL: "GNU Lesser General Public License" (previously known as
"GNU Library General Public License")
b - BSD: The BSD License
a - Artistic license alone
2 - Artistic license 2.0 or later
o - open source: approved by
d - allows distribution without restrictions
r - restricted distribution
n - no license at all
Forces CPAN to perform a task it would normally refuse to do. Force
takes as arguments a method name to be invoked and any number of
additional arguments to pass that method. The internals of the
object get the needed changes so that does not refuse to
take the action. See also the section above on the "force" and the
"fforce" pragma.
Runs a get on the distribution associated with this module.
Returns the filename of the module found in @INC. The first file
found is reported, just as perl itself stops searching @INC once it
finds a module.
Returns the filename of the module found in PERL5LIB or @INC. The
first file found is reported. The advantage of this method over
"inst_file" is that modules that have been tested but not yet
installed are included because PERL5LIB keeps track of tested
Returns the version number of the installed module in readable
Returns the version number of the available module in readable
Runs an "install" on the distribution associated with this module.
Changes to the directory where the distribution associated with this
module has been unpacked and opens a subshell there. Exiting the
subshell returns.
Runs a "make" on the distribution associated with this module.
If module is installed, peeks into the module's manpage, 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 hasn't been installed yet.
Runs a "perldoc" on this module.
Runs a "readme" on the distribution associated with this module.
Calls the reports() method on the associated distribution object.
Runs a "test" on the distribution associated with this module.
Returns 1 if the module is installed and up-to-date.
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 $CPAN::Config->{build_cache} (in MB).
The contents of this cache may be used for later re-installations that
you intend to do manually, but will never be trusted by CPAN itself.
This is due to the fact that the user might use these directories for
building modules on different architectures.
There is another directory ($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
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):
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, i.e. *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
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.
The CPAN program is trying to depend on as little as possible so the
user can use it in hostile environment. It works better the more goodies
the environment provides. For example if you try in the CPAN shell
install Bundle::CPAN
install Bundle::CPANxxl
you will find the shell more convenient than the bare shell before.
If you have a local mirror of CPAN and can access all files with "file:"
URLs, then you only need a perl later 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 a 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 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 $VERSION can be
parsed, please try the above method.
* come as compressed or gzipped tarfiles or as zip files and contain a
"Makefile.PL" or "Build.PL" (well, we try to handle a bit more, but
with little enthusiasm).
Debugging this module is more than a bit complex due to interference
from the software producing the indices on CPAN, the mirroring process
on CPAN, packaging, configuration, synchronicity, and even (gasp!) due
to bugs within the module itself.
For debugging the code of itself in interactive mode, some
debugging aid can be turned on for most packages within with one
o debug package...
sets debug mode for packages.
o debug -package...
unsets debug mode for packages.
o debug all
turns debugging on for all packages.
o debug number
which sets the debugging packages directly. Note that "o debug 0" turns
debugging off.
What seems a successful strategy is the combination of "reload cpan" and
the debugging switches. Add a new debug statement while running in the
shell and then issue a "reload cpan" and see the new debugging messages
immediately without losing the current context.
"o debug" without an argument lists the valid package names and the
current set of packages in debugging mode. "o debug" has built-in
completion support.
For debugging of CPAN data there is the "dump" command which takes the
same arguments as make/test/install and outputs each object's
Data::Dumper dump. If an argument looks like a perl variable and
contains one of "$", "@" or "%", it is eval()ed and fed to Data::Dumper
Floppy, Zip, Offline Mode works nicely without network access, too. If you maintain
machines that are not networked at all, you should consider working with
"file:" URLs. You'll have to collect your modules somewhere first. So
you might use 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. on the non-networked machines works nicely
with this floppy. See also below the paragraph about CD-ROM support.
Basic Utilities for Programmers
Returns true if the module is installed. Used to load all modules into
the running that are considered optional. The config variable
"dontload_list" intercepts the "has_inst()" call such that an optional
module is not loaded despite being available. For example, the
following command will prevent "" from being loaded:
cpan> o conf dontload_list push YAML
See the source for details.
Similary to has_inst() tries to load optional library but also dies if
library is not available
Returns true if the module is installed and in a usable state. Only
useful for a handful of modules that are used internally. See the
source for details.
The constructor for all the singletons used to represent modules,
distributions, authors, and bundles. If the object already exists,
this method returns the object; otherwise, it calls the constructor.
Getter/setter for frontend object. Method just allows to subclass
There's no strong security layer in 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.
But we try to make it easy to add security on demand:
Cryptographically signed modules
Since release 1.77, has been able to verify cryptographically
signed module distributions using Module::Signature. The CPAN modules
can be signed by their authors, thus giving more security. The simple
unsigned MD5 checksums that were used before by CPAN protect mainly
against accidental file corruption.
You will need to have Module::Signature installed, which in turn
requires that you have at least one of Crypt::OpenPGP module or the
command-line gpg tool installed.
You will also need to be able to connect over the Internet to the public
key servers, like, and their port 11731 (the HKP protocol).
The configuration parameter check_sigs is there to turn signature
checking on or off.
Most functions in package CPAN are exported by default. The reason for
this is that the primary use is intended for the cpan shell or for
When the CPAN shell enters a subshell via the look command, it sets the
environment CPAN_SHELL_LEVEL to 1, or increments that variable if it is
already set.
When CPAN runs, it sets the environment variable PERL5_CPAN_IS_RUNNING
to the ID of the running process. It also sets PERL5_CPANPLUS_IS_RUNNING
to prevent runaway processes which could happen with older versions of
When running "perl Makefile.PL", the environment variable
"PERL5_CPAN_IS_EXECUTING" is set to the full path of the "Makefile.PL"
that is being executed. This prevents runaway processes with newer
versions of Module::Install.
When the config variable ftp_passive is set, all downloads will be run
with the environment variable FTP_PASSIVE set to this value. This is in
general a good idea as it influences both Net::FTP and LWP based
connections. The same effect can be achieved by starting the cpan shell
with this environment variable set. For Net::FTP alone, one can also
always set passive mode by running libnetcfg.
Populating a freshly installed perl with one's favorite modules is
pretty easy if you maintain 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 installed for the current perl
interpreter. It's recommended to run this command once only, and from
then on maintain the file manually under a private name, say
Bundle/ With a clever bundle file you can then simply say
cpan> install Bundle::my_bundle
then answer a few questions and go out for coffee (possibly even in a
different city).
Maintaining a bundle definition file means keeping track of two things:
dependencies and interactivity. 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 annoying that so many
distributions need some interactive configuring. So what you can try to
accomplish in your private bundle file is to have the packages that need
to be configured early in the file and the gentle ones later, so you can
go out for coffee after a few minutes and leave to churn away
Thanks to Graham Barr for contributing the following paragraphs about
the interaction between perl, and various firewall configurations. For
further information on firewalls, 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 likely that you
can configure *ncftp* so that it works through your firewall.
Three basic types of firewalls
Firewalls can be categorized into three basic types.
http firewall
This is when the firewall machine runs a web server, and to access
the outside world, you must do so via that web server. If you set
environment variables like http_proxy or ftp_proxy to values
beginning with http://, or in your web browser you've proxy
information set, then you know you are running behind an http
To access servers outside these types of firewalls with perl (even
for ftp), you need LWP or HTTP::Tiny.
ftp firewall
This where the firewall machine runs an 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 "".
To access servers outside these type of firewalls with perl, you
need Net::FTP.
One-way visibility
One-way visibility means these firewalls try to make themselves
invisible to users inside the firewall. An FTP data connection is
normally created by sending your IP address to the remote server and
then listening for the return connection. But the remote server will
not be able to connect to you because of the firewall. For these
types of firewall, FTP connections need to be done in a passive
There are two that I can think off.
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 were
not there.
IP Masquerade
This is when the firewall implemented in the kernel (via NAT, or
networking address translation), it allows you to hide a
complete network behind one IP address. With this firewall no
special compiling is needed as you can access hosts directly.
For accessing ftp servers behind such firewalls you usually need
to set the environment variable "FTP_PASSIVE" or the config
variable ftp_passive to a true value.
Configuring lynx or ncftp for going through a firewall
If you can go through your firewall with e.g. lynx, presumably with a
command such as
/usr/local/bin/lynx -pscott:tiger
then you would configure with the command
o conf lynx "/usr/local/bin/lynx -pscott:tiger"
That's all. Similarly for ncftp or ftp, you would configure something
o conf ncftp "/usr/bin/ncftp -f /home/scott/ncftplogin.cfg"
Your mileage may vary...
1) I installed a new version of module X but CPAN keeps saying, I have
the old version installed
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 previously installed. This is not really a
problem, 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 expectations about
who may install where in the @INC path and who uses which @INC
array. In fine tuned environments "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. Bundle/, install the new
perl with the Configure option prefix, e.g.
./Configure -Dprefix=/usr/local/perl-
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 inspection.
5) I am not root, how can I install a module in a personal directory?
As of CPAN 1.9463, if you do not have permission to write the
default perl library directories, CPAN's configuration process will
ask you whether you want to bootstrap <local::lib>, which makes
keeping a personal perl library directory easy.
Another thing you should bear in mind is that the UNINST parameter
can be dangerous when you are installing into a private area because
you might accidentally remove modules that other people depend on
that are not using the private area.
6) How to get a package, unwrap it, and make a change before building
Have a look at the "look" (!) command.
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 META.yml file or the
generated Makefile. An undetected 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, 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 if all
modules declare the prerequisites correctly with the PREREQ_PM
attribute to MakeMaker or the "requires" stanza of Module::Build.
For bundles which fail and you need to install often, it is
recommended to sort the Bundle definition file manually.
8) In our intranet, we have many modules for internal use. How can I
integrate these modules with but without uploading the
modules to CPAN?
Have a look at the CPAN::Site module.
9) When I run CPAN's shell, I get an error message about things in my
"/etc/inputrc" (or "~/.inputrc") file.
These are readline issues and can only be fixed by studying readline
configuration on your architecture and adjusting the referenced file
accordingly. Please make a backup of the "/etc/inputrc" or
"~/.inputrc" and edit them. Quite often harmless changes like
uppercasing or lowercasing some arguments solves the problem.
10) Some authors have strange characters in their names.
Internally 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> o conf term_is_latin 1
If other charset support is needed, please file a bug report against at and describe your needs. Maybe we can extend
the support or maybe UTF-8 terminals become widely available.
Note: this config variable is deprecated and will be removed in a
future version of It will be replaced with the conventions
around the family of $LANG and $LC_* environment variables.
11) When an install fails for some reason and then I correct the error
condition and retry, refuses to install the module, saying
"Already tried without success".
Use the force pragma like so
force install Foo::Bar
Or you can use
look Foo::Bar
and then "make install" directly in the subshell.
12) How do I install a "DEVELOPER RELEASE" of a module?
By default, CPAN will install the latest non-developer release of a
module. If you want to install a dev release, you have to specify
the partial path starting with the author id to the tarball you wish
to install, like so:
cpan> install KWILLIAMS/Module-Build-0.27_07.tar.gz
Note that you can use the "ls" command to get this path listed.
13) How do I install a module and all its dependencies from the
commandline, without being prompted for anything, despite my CPAN
configuration (or lack thereof)?
CPAN uses ExtUtils::MakeMaker's prompt() function to ask its
questions, so if you set the PERL_MM_USE_DEFAULT environment
variable, you shouldn't be asked any questions at all (assuming the
modules you are installing are nice about obeying that variable as
% PERL_MM_USE_DEFAULT=1 perl -MCPAN -e 'install My::Module'
14) How do I create a Module::Build based Build.PL derived from an
ExtUtils::MakeMaker focused Makefile.PL?
15) I'm frequently irritated with the CPAN shell's inability to help me
select a good mirror.
CPAN can now help you select a "good" mirror, based on which ones
have the lowest 'ping' round-trip times. From the shell, use the
command 'o conf init urllist' and allow CPAN to automatically select
mirrors for you.
Beyond that help, the urllist config parameter is yours. You can add
and remove sites at will. You should find out which sites have the
best up-to-dateness, bandwidth, reliability, etc. and are
topologically close to you. Some people prefer fast downloads,
others up-to-dateness, others reliability. You decide which to try
in which order.
Henk P. Penning maintains a site that collects data about CPAN
Also, feel free to play with experimental features. Run
o conf init randomize_urllist ftpstats_period ftpstats_size
and choose your favorite parameters. After a few downloads running
the "hosts" command will probably assist you in choosing the best
mirror sites.
16) Why do I get asked the same questions every time I start the shell?
You can make your configuration changes permanent by calling the
command "o conf commit". Alternatively set the "auto_commit"
variable to true by running "o conf init auto_commit" and answering
the following question with yes.
17) Older versions of had the original root directory of all
tarballs in the build directory. Now there are always random
characters appended to these directory names. Why was this done?
The random characters are provided by File::Temp and ensure that
each module's individual build directory is unique. This makes
running in concurrent processes simultaneously safe.
18) Speaking of the build directory. Do I have to clean it up myself?
You have the choice to set the config variable "scan_cache" to
"never". Then you must clean it up yourself. The other possible
values, "atstart" and "atexit" clean up the build directory when you
start (or more precisely, after the first extraction into the build
directory) or exit the CPAN shell, respectively. If you never start
up the CPAN shell, you probably also have to clean up the build
directory yourself.
OLD PERL VERSIONS is regularly tested to run under 5.005 and assorted newer
versions. It is getting more and more difficult to get the minimal
prerequisites working on older perls. It is close to impossible to get
the whole Bundle::CPAN working there. If you're in the position to have
only these old versions, be advised that CPAN is designed to work fine
without the Bundle::CPAN installed.
To get things going, note that GBARR/Scalar-List-Utils-1.18.tar.gz is
compatible with ancient perls and that File::Temp is listed as a
prerequisite but CPAN has reasonable workarounds if it is missing.
This module and its competitor, the CPANPLUS module, are both much
cooler than the other. is older. CPANPLUS was designed to be
more modular, but it was never intended to be compatible with
In the year 2010 App::cpanminus was launched as a new approach to a cpan
shell with a considerably smaller footprint. Very cool stuff.
This software enables you to upgrade software on your computer and so is
inherently dangerous because the newly installed software may contain
bugs and may alter the way your computer works or even make it unusable.
Please consider backing up your data before every upgrade.
Please report bugs via <>
Before submitting a bug, please make sure that the traditional method of
building a Perl module package from a shell by following the
installation instructions of that package still works in your
Andreas Koenig "<>"
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See <>
Kawai,Takanori provides a Japanese translation of a very old version of
this manpage at <>
Many people enter the CPAN shell by running the cpan utility program
which is installed in the same directory as perl itself. So if you have
this directory in your PATH variable (or some equivalent in your
operating system) then typing "cpan" in a console window will work for
you as well. Above that the utility provides several commandline
melezhik (Alexey) sent me a link where he published a chef recipe to
work with