Ruby User's Guide

Getting started

First, you'll want to check whether ruby is installed. From the shell prompt (denoted here by "%", so don't type the %), type

% ruby -v

(-v tells the interpreter to print the version of ruby), then press the Enter key. If ruby is installed, you will see a message something like the following:

% ruby -v
ruby 1.8.3 (2005-09-21) [i586-linux]

If ruby is not installed, you can ask your administrator to install it, or you can do it yourself, since ruby is free software with no restrictions on its installation or use.

Now, let's play with ruby. You can place a ruby program directly on the command line using the -e option:

% ruby -e 'puts "hello world"'
hello world

More conventionally, a ruby program can be stored in a file.

% echo "puts 'hello world'" > hello.rb
% ruby hello.rb
hello world

When writing more substantial code than this, you will want to use a real text editor!

Some surprisingly complex and useful things can be done with miniature programs that fit in a command line. For example, this one replaces foo with bar in all C source and header files in the current working directory, backing up the original files with ".bak" appended:

% ruby -i.bak -pe 'sub "foo", "bar"' *.[ch]

This program works like the UNIX cat command (but works slower than cat):

% ruby -pe 0 file

Copyright (c) 2005-2008 Mark Slagell

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

A copy of the license is included in the section entitled "GNU Free Documentation License."