A CPAN client that works like a charm

The Comprehensive Perl Archive Network (CPAN) is a collection of freely available Perl modules.

Read this article to know how to configure and use a CPAN client.

cpan

Perl comes with a builtin CPAN client, named ehm … cpan.

Be aware that your configuration is stored in the ~/.cpan/CPAN/MyConfig.pm file.

Do not edit that file, use o conf instead from the cpan interactive shell, see below.

First run

It is really easy to start, just launch 

$ cpan
CPAN.pm requires configuration, but most of it can be done automatically.
If you answer 'no' below, you will enter an interactive dialog for each
configuration option instead.
Would you like to configure as much as possible automatically? [yes]

and hit enter (two times) to accept defaults. It will be enough to let you prompt into an interactive shell so you can start install modules.

Give it a try installing Perl::Tidy

cpan[1]> install Perl::Tidy

If it ends with an OK you are done, just type q to exit interactive shell.

...
  SHANCOCK/Perl-Tidy-20130922.tar.gz
  /home/bi/software/make/current/bin/make install  -- OK
cpan[2]> q
Terminal does not support GetHistory.
Lockfile removed.

Continue with Configuration if cpan is working and you want to configure it to achieve greater user experience

or go to cpanminus if you want a zero config, minimal and efficient CPAN client

otherwise read Troubleshooting if you had problems during installation.

Troubleshooting

ATTENTION

Two things could not work: network and/or permissions.

The quickest workaround is to check your network configuration and launch commands using sudo.

I really recommend to avoid using cpan and perl provided by your system. See Install your own Perl with your own CPAN or .software to know how to install Perl in some location your user owns.

local::lib approach

By the way, cpan will realize if you have not write permission and will ask what approach do you want: default is local::lib that is a good idea if you don’t want to build your own Perl.

For example, I use it on Codio and works great: just keep hitting enter and cpan will install local::lib for you.

After installation, you need to modify your environment manually. Just launch

$ cd ~/perl5/lib/perl5
$ perl -Mlocal::lib >> ~/.bash_profile
$ source ~/.bash_profile # or reconnect

Help

Just type h in a cpan shell

cpan> h
Display Information                                                  (ver 2.00)
 command  argument          description
 a,b,d,m  WORD or /REGEXP/  about authors, bundles, distributions, modules
 i        WORD or /REGEXP/  about any of the above
 ls       AUTHOR or GLOB    about files in the author's directory
    (with WORD being a module, bundle or author name or a distribution
    name of the form AUTHOR/DISTRIBUTION)
Download, Test, Make, Install...
 get      download                     clean    make clean
 make     make (implies get)           look     open subshell in dist directory
 test     make test (implies make)     readme   display these README files
 install  make install (implies test)  perldoc  display POD documentation
Upgrade
 r        WORDs or /REGEXP/ or NONE    report updates for some/matching/all modules
 upgrade  WORDs or /REGEXP/ or NONE    upgrade some/matching/all modules
Pragmas
 force  CMD    try hard to do command  fforce CMD    try harder
 notest CMD    skip testing
Other
 h,?           display this menu       ! perl-code   eval a perl command
 o conf [opt]  set and query options   q             quit the cpan shell
 reload cpan   load CPAN.pm again      reload index  load newer indices
 autobundle    Snapshot                recent        latest CPAN uploads

Configuration

You can reconfigure all cpan client options by launching

cpan> o conf init
CPAN.pm requires configuration, but most of it can be done automatically.
If you answer 'no' below, you will enter an interactive dialog for each
configuration option instead.
Would you like to configure as much as possible automatically? [yes] no
type **no** and follow instructions. In particular, if you need *cpan* pick mirrors for you, launch 
 cpan> o conf init urllist
and hit enter.

Get CPAN latest version

STRONGLY RECOMMENDED

First of all, make sure you have CPAN.pm module updated to latest version

cpan> install CPAN
...
cpan> reload CPAN

Autocommit

OPTIONAL

Always commit changes to config variables to disk.

cpan> o conf auto_commit 1
For the rest of this article I assume auto_commit is on.
Note that auto_commit is disabled by default, so you should launch o conf commit to confirm configuration changes.

Command number in prompt

PERSONAL

Disable the command number in the prompt.

 cpan> o conf commandnumber_in_prompt 0

Enable history

RECOMMENDED

You need to install the following modules

 cpan> install Term::ReadLine::Perl Term::ReadKey

YAML

RECOMMENDED

Install YAML Perl module

 cpan> install YAML

and try to install a faster YAML implementation

 cpan> install YAML::XS

It will need a C compiler installed on your system. If installation is successful, tell cpan which YAML implementation you prefer.

 cpan> o conf yaml_module YAML::XS

LWP

RECOMMENDED

Make sure LWP is installed and up to date

 cpan> install LWP

so cpan will use it to fetch files from Internet.

CPAN::SQLite

OPTIONAL

CPAN::SQLite is a layer between the index files that are downloaded
from the CPAN and CPAN.pm that speeds up metadata queries and reduces memory consumption of CPAN.pm considerably.

To use CPAN::SQLite launch

 cpan> install CPAN::SQLite
 cpan> o conf use_sqlite yes

Build prerequisites automatically

RECOMMENDED

The CPAN.pm module can detect when a module which you are trying to build depends on prerequisites. If this happens, I prefer it builds the prerequisites automatically instead of asking for confirmation.

I prefer to install prerequisites also when it is only needed for building or testing in order to save time on future installations.

 cpan> o conf prerequisites_policy follow
 cpan> o conf build_requires_install_policy yes

Enable colors

PERSONAL

 cpan> o conf colorize_output yes
 cpan> o conf colorize_print bold white on_black
 cpan> o conf colorize_warn bold red on_black
 cpan> o conf colorize_debug green on_black

or choose your favourite colors

 cpan> o conf init /colorize/

Character set

PERSONAL

In general, CPAN is English speaking territory, so the character set does not matter much but some modules have names that are outside the ASCII range. Since my terminal supports UTF-8, I set

 cpan> o conf term_is_latin no

Upgrade modules

Print modules that can be upgraded.

 cpan> r

and

 cpan> upgrade

Both commands accept a /regexp/ as argument. See Help.

cpanminus

App::cpanminus is a gift from Perl community angel Tatsuhiko Miyagawa.

It’s dependency free (can bootstrap itself), requires zero configuration, and stands alone. When running, it requires only 10MB of RAM.

I assuming you already has a working cpan client, so to install cpanminus just launch

$ cpan App::cpanminus

and use cpanm instead of cpan from now on. It is light, fast and minimal CPAN client, but, it has many features too: see cpanm or cpanm -h to see what cpanminus can do.

You can use App::cpanoutdated to detect outdated CPAN modules in your environment.

Install it

$ cpanm App::cpanoutdated

then update all modules with

$ cpan-outdated | cpanm

Note that also cpan has the upgrade modules feature but cpan-outdated is faster, uses less memory and is integrated with cpanm.

See also

  • Learn Perl - CPAN and Perl Configuration Howto
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