App::local::lib::helper(3)

NAME
App::local::lib::helper - Make it easy to run code against a local-lib

SYNOPSIS
Installing and using the helper (common usage)

    cpanm --local-lib ~/mylib App::local::lib::helper
    ~/mylib/bin/localenv bash

Customizing the helper creation (advanced use only)

    use App::local::lib::helper;
    App::local::lib::helper->run(%opts);

Note, if you don't have "cpanm" already installed you can use the web service version like so instead for all examples:

    curl -L http://cpanmin.us/ | perl - --local-lib ~/mylib App::local::lib::helper

DESCRIPTION
This is an object which provide the functionality to create a local::lib 'helper' script in either the currently loaded local::lib environment or in a target directory of choice. By default the script is called "localenv" and can be used to invoke a command under the local::lib which it was built against. For example, assume you build a local::lib like so:

    cpanm --local-lib ~/mylib App::local::lib::helper

Note what is happening. First, you are telling cpanminus to install everything to a local::lib directory called "~/mylib" (cpanminus behind the scenes uses local::lib to do this for you) then you are telling cpanminus to install the distribution App::local::lib::helper into that created local::lib directory. When the "Makefile.PL" script for App::local::lib::helper runs, it notices the fact that it is being asked to install into a locally lib managed directory and will additionally generate a helper script into "~/mylib/bin" called "localenv".

Now, if you want to invoke a perl application and use libs installed into "~/mylib", you can do so like:

    ~/mylib/bin/localenv perl [SOME COMMAND]

The command "localenv" will make sure the same local::lib that was active when App::local::lib::helper was originally installed is again installed into the environment before executing the commands passed in @ARGV. Upon completing the command, the %ENV is restored so that you can use this to fire off an application against a specific local::lib without needing to deal with the details of how to activate the local::lib or how to make sure your %ENV stays clean.

The arguments given to "localenv" don't need to be a perl application. For example, I often like to open a sub shell under a particular local::lib managed directory.

    ~/mylib/bin/localenv bash

Now, if I do:

    perl -V

I'll see that i"~/mylib" has been added to @INC. Additionally, "~/mylib/bin" will have been added to $PATH, so that any command line perl applications installed into the local::lib (such as "ack" or "cpanm") can be accessed easily.

Another example usage would be when you want to install an application from CPAN, install it and all its dependencies to a single directory root and then run it without a lot of effort. For example:

    cpanm --local-lib ~/gitalyst-libs Gitalist App::local::lib::helper
    ~/gitalyst-libs/bin/localenv gitalyst-server.pl

And presto! Your cpan installed application is running, fully self-contained to one root directory all under regular user privileges.

local::lib does all the real work, but I find this to be the easiest way to run given code against a local::lib root.

  Additional Helpers
In addition to the "localenv" script which is documented above, we also create two snippets of code suitable for including in your ".bashrc" or ".cshrc". These are created to help people that only want or need a single local lib and would like to activate it at login. If you'd like to use these, simple add the following tot he end of your ".bashrc"

    source $TARGET/bin/localenv-bashrc

Where $TARGET is the root of your local lib (the directory that contains your "bin" and "lib" directories created when you ran the helper).

Next time you log in, you can do "perl -V" and should see that your local-lib has automatically been activated.

There will also be a "source $TARGET/bin/localenv-cshrc" created for those of you using csh. Currently this is not going to work with Windows shell users, but should be easy to setup, collaborations very welcomed.

OPTIONS
This class supports the following options.

which_perl
    This should be the path to the perl binary that the local::lib is built against. This defaults to the path of the perl binary under which we are currently running. You should probably leave this one alone :)

target
    This is the target directory for the local::lib you want to build the helper script against. By default it will attempt to detect the currently running local::lib and use that. If we can't detect a running local::lib and this option is undef, we die with a message.

helper_name
    This is the name of the helper utility script. It defaults to 'localenv'.

helper_permissions
    These are the permissions the the helper utility script is set to. By default we set the equivilent of 'chmod 755 [HELPER SCRIPT]'

HELPERS
This distribution installs the following local::lib helpers

  localenv
This is a perl script that runs a single command in local::lib aware context. You can use the "helper-name" option to set a different name.

Typically I will use this to 'enable' a previously setup local::lib with commands like:

    ~/mylocallib/bin/localenv bash
    ~/mylocallib/bin/localenv screen

Or I can use it to run a single command wrapped in the local::lib target and exit cleanly:

    ~/mylocallib/bin/localenv perl app.pl
    ~/mylocallib/bin/localenv plackup app.psgi

  localenv-relative
NOTE: Experimental feature. Please prefer using "localenv" unless you absolutely need this functionality.

This perl script functions (or should function) identically to localenv as documented. However, instead of having hardcoded full paths to your Perl binary and local::lib target directories, we instead try to use relative pathing. For example, here is the helper script built on my server for the standard "localenv" script:

    #!/Users/johnn/perl5/perlbrew/perls/perl-5.14.1/bin/perl

    use strict;
    use warnings;

    use lib '/Users/johnn/locallib_5_14_1/lib/perl5';
    use local::lib '/Users/johnn/locallib_5_14_1';

    unless ( caller ) {
        if ( @ARGV ) {
            exec @ARGV;
        }
    }

And here is the example same version for the relative script:

    #!/usr/bin/env perl

    use strict;
    use warnings;

    use FindBin;
    use File::Spec;
    use lib File::Spec->catdir($FindBin::Bin, '..', 'lib', 'perl5');
    use local::lib File::Spec->catdir($FindBin::Bin, '..');

    unless ( caller ) {
        if ( @ARGV ) {
            exec @ARGV;
        }
    }

The goal here is to be more friendly when you need to relocate your installation of Perl and/or your local::lib target directory. You might wish to try this if you are copying a 'seed' Perl and local::lib setup to multiple developer home directories (as a way to speed up first time developer setup, for example) or if your deployment system copies your application from your build enviroment to a QA or Production that is not identical.

Personally I prefer to build Perl and my application in each location that is different, since I find that works very effectively. However I understand some shops have existing build systems that deploy code by copying Perl dependencies from box to box, and these boxes are not always identical in directory layout. For example, there might be a build or integration point in development, with a local::lib target of "/home/integration/webapp-cpan-locallib" and you wish to copy that directory recursively to your qa/production server, which might be located at "/home/qa/local-lib".

I'd like to accomodate this approach as best I can, however I can't be certain that moving Perl and local::lib around rather than performing a true install is going to work consistently. Caveat emptor!

Please also note that the following shell snippets are not relative tested.

  localenv-bashrc
a snippet suitable for sourcing in your .bashrc, which will automatically activate a local-lib at login. Name will follow from "helper-name".

Here's an example of the line I might add to .bashrc (assumes you have setup local::lib in "$HOME/mylocal"

    source $HOME/mylocal/localenv-bashrc

Then next time you open a shell you should see that $PATH and "PERL5LIB" have been properly changed.

  localenv-cshrc
a snippet suitable for sourcing in your .cshrc, which will automatically activate a local-lib at login. Name will follow from "helper-name".

AUTHOR
John Napiorkowski " <<jjnapiork@cpan.org"> >

COPYRIGHT & LICENSE
Copyright 2011, John Napiorkowski

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.