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Sun, 27 Nov 2016

Perl 6 By Example: Running Rakudo


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This blog post is part of my ongoing project to write a book about Perl 6.

If you're interested, please sign up for the mailing list at the bottom of the article, or here. It will be low volume (less than an email per month, on average).


Before we start exploring Perl 6, you should have an environment where you can run Perl 6 code. So you need to install Rakudo Perl 6, currently the only actively developed Perl 6 compiler. Or even better, install Rakudo Star, which is a distribution that includes Rakudo itself, a few useful modules, and an installer that can help you install more modules.

Below a few options for getting Rakudo Star installed are discussed. Chose whatever works for you.

The examples here use Rakudo Star 2016.10.

Installers

You can download installers from http://rakudo.org/downloads/star/ for Mac OS (.dmg) and Windows (.msi). After download, you can launch them, and they walk you through the installation process.

Note that Rakudo is not relocatable, which means you have to install to a fix location that was decided by the creator of the installer. Moving the installation to a different directory.

On Windows, the installer offers you need to add C:\rakudo\bin and C:\rakudo\share\perl6\site\bin to your PATH environment. You should chose that option, as it allows you to call rakudo (and programs that the module installer installs on your behalf) without specifying full paths.

Docker

On platforms that support Docker, you can pull an existing Docker container from the docker hub:

$ docker pull rakudo-star

Then you can get an interactive Rakudo shell with this command:

$ docker run -it rakudo-star perl6

But that won't work for executing scripts, because the container has its own, separate file system. To make scripts available inside the container, you need to tell Docker to make the current directory available to the container:

$ docker run -v $PWD:/perl6 -w /perl6 -it rakudo-star perl6

The option -v $PWD:/perl6 instructs Docker to mount the current working directory ($PWD) into the container, where it'll be available as /perl6. To make relative paths work, -w /perl6 instructs Docker to set the working directory of the rakudo process to /perl6.

Since this command line starts to get unwieldy, I created an alias (this is Bash syntax; other shells might have slightly different alias mechanisms):

alias p6d='docker run -v $PWD:/perl6 -w /perl6 -it rakudo-star perl6'

I put this line into my ~/.bashrc files, so new bash instances have a p6d command, short for "Perl 6 docker".

As a short test to see if it works, you can run

$ p6d -e 'say "hi"'
hi

If you go the Docker route, just the p6d alias instead of perl6 to run scripts.

Building from Source

To build Rakudo Star from source, you need make, gcc or clang and perl 5 installed. This example installs into $HOME/opt/rakudo-star:

$ wget http://rakudo.org/downloads/star/rakudo-star-2016.10.tar.gz
$ tar xzf rakudo-star-2016.10.tar.gz
$ cd rakudo-star-2016.10/
$ perl Configure.pl --prefix=$HOME/opt/rakudo-star --gen-moar
$ make install

You should have about 2GB of RAM available for the last step; building a compiler is a resource intensive task.

You need to add paths to two directories to your PATH environment variable, one for Rakudo itself, one for programs installed by the module installer:

PATH=$PATH:$HOME/opt/rakudo-star/bin/:$HOME/opt/rakudo-star/share/perl6/site/bin

If you are a Bash user, you can put that line into your ~/.bashrc file to make it available in new Bash processes.

Testing your Rakudo Star Installation

You should now be able to run Perl 6 programs from the command line, and ask Rakudo for its version:

$ perl6 --version
This is Rakudo version 2016.10-2-gb744de3 built on MoarVM version 2016.09-39-g688796b
implementing Perl 6.c.

$ perl6 -e "say <hi>"
hi

If, against all odds, all of these approaches have failed you to produce a usable Rakudo installation, you should describe your problem to the friendly Perl 6 community, which can usually provide some help. http://perl6.org/community/ describes ways to interact with the community.

Next week we'll take a look at the first proper Perl 6 example, so stay tuned for updates!

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