18 November 2010

Install & Use Perl Modules as Non-Root

Perl is an indispensable tool in my arsenal.

My reasons to install Perl into $HOME are

• On departmental machines where I am not root or any other privileged users.
• Even if I can obtain root privilege, installing Perl modules to my home directory makes it easy to move among machines: NFS-ed $HOME or packing with a tarball.

Configure CPAN Module

Create $HOME/.perl for your local Perl modules.

mkdir $HOME/.perl

Start CPAN shell with either cpan or perl -MCPAN -e shell. Follow the prompt to initialize it. We can come back to the initialization procedure by issuing

o conf init

inside the shell.

Once in the shell, we can poke around by

h  # help for the shell
o conf /mbuild/   # Search for regex /build/ -> Module::Build
o conf /make/  # Search for regex /make/ -> Ext::UtilMakeMaker

Now comes the key configurations

o conf mbuildpl_arg "installdirs=site install_base=$HOME/.perl"
o conf makepl_arg "INSTALLDIRS=site INSTALL_BASE=$HOME/.perl"
o conf prefer_installer MB
o conf prerequisites_policy follow
o conf commit

• mbuildpl_arg is the argument passing to perl Build.PL for Module::Build.
• makepl_arg is the argument passing to perl Makefile.PL for ExtUtils::MakeMaker.
• prefer_installer can be either MB (for Module::Build) or MM (for MakeMaker) and MB is preferred.
• o conf prerequisites_policy follow makes the CPAN module automatically install ("follow") build/runtime dependencies, which saves us from the chore of confirming installation for each dependency. See CPAN for an explanation.
• o conf commit stores the configuration in a hash $CPAN::Config (e.g., in a module $HOME/.cpan/CPAN/MyConfig.pm, which you can edit by hand). See CPAN for an explanation.

Install Perl Modules

With proper configuration, installation is as simple as either

cpan -i MODULE
perl -MCPAN -e 'install PKG'

at system shell or

install MODULE

at CPAN shell.

To make CPAN module easier to use, follow the suggestions here, we install the following modules

cpan -i Term::ReadLine::Perl Term::ReadKey

to enable history and command completion functionalities.

Use Local Modules

perlrun explains how perl locates libraries.

With colon-separated (semicolon-separated under Windows) list of search path in PERL5LIB environment variable, we make perl and perdoc aware of our locally installed modules.

We can export PERL5LIB in $HOME/.bashrc, $HOME/.xinitrc, or $HOME/.xsession with

export PERL5LIB=$HOME/.perl:$HOME/.perl/lib/perl5:$PERL5LIB

We do not need to add the architecture-specific directory here because, according to here, "... any architecture-specific directories under the specified locations are automatically included if they exist (this lookup being done at interpreter startup time) ..."

Do not forget to source the script, e.g.,

source $HOME/.bashrc

We can check perl is aware of PERL5LIB by

perl -le 'print qq(@INC)'

Reference

CPAN, Module::Build, ExtUtils::MakeMaker.

Sear Perl documentation.