Perl – CPAN first launching configuration

cpanperl

I'm taking a look into Perl as a total beginner. I want to try some CPAN modules.
When I run an install command on my Osx console, CPAN asks for a configuration with the following statement :

To install modules, you need to configure a local Perl library
directory or escalate your privileges. CPAN can help you by
bootstrapping the local::lib module or by configuring itself to use
'sudo' (if available). You may also resolve this problem manually if
you need to customize your setup.

What approach do you want? (Choose 'local::lib', 'sudo' or 'manual')

What is the difference between local::lib and sudo options ?
If I understand it well, it installs some modules locally on my computer. But I don't see any difference between the two config above.

Best Answer

If you use sudo, CPAN will use root to install the libraries in a central location where all users on the machine can access the files without any special configuration. If you use 'local::lib', it will create a library in your home directory and install the modules such that only perl programs that have been configured to look for modules in your home directory will find the modules.

Perl uses the special variable @INC to search for module paths. So you can install modules anywhere as long as you set @INC properly before you use them. This article explains the basics.

http://www.symkat.com/find-a-perl-modules-path

You can do all kinds of fun stuff with @INC; one of my favorite hacks it to put a function pointer in there and use custom perl code to lookup modules.

Related Solutions

Macos – Two versions of Perl in Mac OS X

OS X ships with two versions of Perl. 5.10.0 is the default, so /usr/bin/perl and /usr/bin/cpan should all talk to 5.10.0.

The problem is you have three. /opt/local indicates a MacPorts installation which probably installed Perl as a dependency when you weren't looking. That's /opt/local/bin/perl and its probably the default perl in your path. Check with which perl. That also means you're probably using MacPorts' cpan, check with which cpan, and thus installed Template Toolkit into the MacPorts version.

I'm going to guess either you're running a program with #!/usr/bin/perl at the top or you're using the built in mod_perl or you're running it as a user who is not you. All of which will reference OS X's default Perl and not your MacPorts install.

Macports has a 5.10 as well as 5.12, but "perl" in Macports is still 5.8. You can install 5.10 in Macports.

As to how to resolve this... if you're using using mod_perl on that machine, use Macports' Perl. It will be easier to install modules and it will be kept up to date better than the OS version.

To shield yourself from future confusion, you can add aliases into /usr/local/bin or ~/bin to perl, perldoc and cpan to the Perl of your choice. That will prevent something else from installing perl in your path and hijacking.

Linux – when using CPAN in linux ubuntu should I run it using sudo / as root or as the default user

You should run the cpan command as your normal user. You have two choices:

Install modules into a directory under your home dir. local::lib will help you set that up.
Configure cpan to use sudo during the install phase. You do that by starting the cpan shell and typing:
```
o conf make_install_make_command 'sudo make'
o conf mbuild_install_build_command 'sudo ./Build'
o conf commit
```
The first line configures MakeMaker to use sudo. The second line does the same for Module::Build. The third line saves the changes.

Best Answer

Related Solutions

Macos – Two versions of Perl in Mac OS X

Linux – when using CPAN in linux ubuntu should I run it using sudo / as root or as the default user

Related Topic