use Modern::Perl;

How to set-up your own CPAN mirror

2009-11-29T07:51:05Z

Are you a sysadmin and you're running servers with a lot of Perl code and Perl modules installed? You are a Perl hacker, who wish to access the complete CPAN repository on his notebook even when not connected to the internet?

Why not set-up your own CPAN-Mirror then? It's really easy.

]]> All you need is to install the Perl module called CPAN::Mini.

cpan CPAN::Mini

will do that for you.

Here is a little Perl Script that Mirrors the CPAN Mirror of your choice to your local hard-drive:

#!/usr/bin/env perl

$> = 33;        # switch effective user id to www-data

use CPAN::Mini;

CPAN::Mini->update_mirror(

   remote => "ftp://ftp.cpan.org/pub/CPAN", 

   local  => "/var/www/localhost/mirrors/cpan",

   trace  => ($ARGV[0] ? 1 : 0)

);

The trace option will active debug output. If you call your little cpan-mirror script with whatever command line argument, it will tell CPAN::Mini to print out some activity log. If you call it without any argument, it will be silent - which is nice when running as a cronjob.

Alternatively you could go and use the "minicpan" command line tool that comes with the CPAN::Mini bundle (installs to /usr/local/bin by default). Type in "perldoc minicpan" for details how to use it.

Next, you should make sure that you can reach your CPAN-Mirror via HTTP or FTP. This means you should make sure to mirror into a directory that can be accessed by your local web- or ftp-server.

Then, go and tell your CPAN shell to use your mirror. Type in "cpan" to start the CPAN shell.

cpan[1]> o conf urllist 'http://localhost/mirrors/cpan/' 'ftp://ftp.cpan.org/pub/CPAN' 'ftp://ftp.funet.fi/pub/languages/perl/CPAN'
cpan[2]> o conf commit

You should specify your local web- or ftp-server as first argument in the list of CPAN mirrors. Add as many mirrors as you like. A full list of CPAN mirrors in your country can be obtained here.

Perl6::Junction

2009-11-28T06:10:09Z

Today I'd like to introduce you a Perl module I really like and use a lot in my code. It's called Perl6::Junction and you can get it from CPAN.

Please have a look what it can do for you.

]]> Perl6::Junction comes in when you're working on Arrays. For example, if you'd like to search your array if it contains a defined element, usually your code will look like this:

my @animal = ('squirrel', 'cat', 'catfish', 'sausage-dog', 'guinea pig', 'pig');

# using a foreach loop to walk trough all array elements

#

foreach my $animal ( @animal ) {

    if ( $animal eq 'guinea pig' ) {

        # found my lovely guinea pig in this group of animals!

        last;

    }

}

# you could also go and use grep to search your array

#

if ( grep(/^guinea pig$/, @animal) ) {

    # found it!

}

But especially grep is not easy to use for beginners and one could make many mistakes when using it.

For example, just calling grep like grep('cat', @animal) will match every string in the array because it excepts a BLOCK or regular expression and not a string as first argument and interprets the string as 'TRUE' which matches everything.

Doing a grep(/cat/, @animal) will match every array element that contains the string 'cat'. It would match 'cat' and 'catfish' in this example.

Most of the time, this is not really what you want.

When using Perl6::Junction it becomes as easy as this:

use Perl6::Junction qw( all any none one );

my @animal = ('squirrel', 'cat', 'catfish', 'sausage-dog', 'guinea pig', 'pig');

if ( any(@animal) eq 'guinea pig' ) {

    # one or more guinea pig's in the list of animals!

}

if ( one(@ainmal) eq 'guinea pig' ) {

    # exactly one guinea pig in the list

}

my @herd = ('sheep', 'sheep', 'wolf', 'sheep', 'sheep');

unless ( all(@herd) eq 'sheep' ) {

    # watch out!

}

Pretty nice, right? :)

If I caught your interest, please have a look at more examples in the modules documentation at CPAN.

How to install Perl Modules from CPAN in the Unix user-space

2009-11-27T17:12:00Z

If you're a sysadmin or if you run a Perl software development environment, you might want to give your users or developers the possibility to install Perl modules from CPAN into their private user-space. This could be helpful for trying out new modules or playing around with modules that might be used in production at a later time. Or, if a developer wants to test a new version of a module without overwriting the system-wide installed version of that module.

Here is a step by step instruction how you could set-up user-space CPAN support.

]]> In the home-directory of the user, you need to create a file called

~/.cpan/CPAN/MyConfig.pm

which is a customized configuration file for the CPAN shell. If you like, you could use the system-wide CPAN config as a template for this file and just overwrite the appropriate attributes.

One way to find the system wide CPAN config is by running a

locate CPAN/Config.pm

and then copy the file over to ~/.cpan/CPAN/MyConfig.pm. Open the MyConfig.pm file in the editor of your choice and change the following lines:

'build_dir' => qq[$ENV{HOME}/.cpan/build],
'cpan_home' => qq[$ENV{HOME}/.cpan],
'histfile' => qq[$ENV{HOME}/.cpan/histfile],
'keep_source_where' => qq[$ENV{HOME}/.cpan/sources],
'makepl_arg' => q[PREFIX=~/lib/perl5 LIB=~/lib/perl5/lib INSTALLMAN1DIR=~/lib/perl5/man1 INSTALLMAN3DIR=~/lib/perl5/man3]
'mbuild_arg' => qq[--extra_linker_flags -L$ENV{HOME}/lib],
'mbuildpl_arg' => qq[--install_base $ENV{HOME}],

If you like to use a special CPAN mirror (maybe your own local mirror server) for the user, then also change the following line in MyConfig.pm:

'urllist' => [q[http://cpan.mirror1.mydomain.com/], q[http://cpan.mirror2.mydomain.com/]],

Next you need to create the directories where the user-space Perl modules and man-pages will be installed to:

~/lib/perl5/bin
~/lib/perl5/lib
~/lib/perl5/man

At last, you need to put the following lines into the users ~/.bash_profile (or whatever file your shell runs at login) file:

export PERL5LIB=${PERL5LIB}:~/lib/perl5/lib
export MANPATH=~/lib/perl5/man

which tells the Perl interpreter to look for modules first in ~/lib/perl5/lib and then search in the system wide directories. The same goes for the man-pages, which are living in ~/lib/perl5/man.

To give your new set-up a try, login with the user-account and install the following module:

cpan Acme::Bleach

and see if you can use it

man Acme::Bleach
perl -e 'use Acme::Bleach;'

One more thing :)

If you copy your brand-new set-up to /etc/skel

/etc/skel/.cpan/CPAN/MyConfig.pm
/etc/skel/.bash_profile
/etc/skel/lib/perl5
/etc/skel/lib/perl5/lib
/etc/skel/lib/perl5/bin
/etc/skel/lib/perl5/man

it will be installed automatically for each new Unix user that you create.

How to install a Perl Module from CPAN

2009-11-26T19:29:03Z

Developers and admins who are new to Perl might wonder how they can install one of the 18.000 available Perl Modules from http://search.cpan.org.

One of the many ways to do this is to call the CPAN shell from the Unix command line, like so:

cpan Modern::Perl

You could also go and give the cpan command a list of modules that you like to install:

cpan Modern::Perl DBI YAML JSON::XS

However, if you just type in "cpan" you start the interactive CPAN shell, where you can install a module by typing:

install Modern::Perl

If you just type in “i Modern::Perl” you get just some information about the module.

The CPAN shell downloads the archive into your ~/.cpan/build directory and extracts the content there. If the module can not be installed because tests are failing, you could go into that directory and do a

perl Makefile.PL
make
make test
make install

by hand and eventually fix the problem that caused the tests to fail - or just force to install the module and ignore the tests if you know what you’re doing.