RubyGeneral

From Rory.wiki

Ruby Debugging

tutorial Very handy for examining problems in complex apps (eg metasploit) per the tuorial require 'ruby-debug' at the top of the source file and place the keyword debugger in the file just before the error.

Then use p command to evaluate statements (or pp for a more structured output) , var local shows the local variables and their values. another tutorial on ruby-debug

Ruby Error Handling

tutorial on error handling

general syntax is

begin
  statements that might need rescuing
rescue <error_class> => variable_name
  puts variable_name.message
end

Timeout Module

Useful for rescuing tasks that might be long running and fail (eg mechanize jobs on unreliable websites) module docs

general syntax is

begin
  variable_name = Timeout::timeout(timeout_in_seconds) {code_which_might_timeout}
rescue Timeout::Error
  some_nice_rescue_stuff_here
end

classes and calling from command line

If you've got a class in a file and want to be able to call if from irb and also the command line

for the script lines to instantiate the class wrap them in

class MyClass
  def initialize
    some_stuff_here
  end
 
  def run
    some_more_stuff_here
  end
end
if __FILE__ == $0
 object = MyClass.new
 object.run
end

Running system commands from ruby scripts

From here and here. If you're running system programs from the OS and you need to process the results the best way is

%x[<system_command>]

if you need to insert variables into the command use #{<variable>} . If you need to capture STDERR from the command as well as STDOUT use

%x[<system_command> 2>&1]

irb

• It's worth noting that if there's a problem with loading .irbrc (for example a missing gem file) then it'll fail silently by default (well on ubuntu anyway). So if your methods/colouring aren't working all of a sudden it's worth investigating by checking the code being loaded in there.

.irbrc

colorization is provided by wirble (you need to install the gem first)

require 'irb/completion'
require 'rubygems'
require 'wirble'
 
colors = Wirble::Colorize.colors.merge({
        :object_class => :black,
        :class => :dark_grey,
        :symbol => :red,
        :symbol_prefix => :blue,
})
 
Wirble::Colorize.colors = colors
Wirble.init
Wirble.colorize
 
 
ARGV.concat [ "--readline", "--prompt-mode", "simple"]
 
class Object
  def mymethods
    (self.methods - Object.new.methods).sort
  end
end

quieting IRB return values

if you commonly work with large text files in IRB, then reading them in can be a pain as the return value from the .read or .readlines method is huge. You can restrict the size of the return value displayed in irb as mentioned here

conf.return_format = "=> %.512s\n"

where 512 is the number of characters to display

Links

Loads of IRB resources

More IRB stuff

Stack Overflow Post on irb tricks

Another post on irb tricks

Metaprogramming Stuff

Mainly from here

Finding a list of the public instance methods for a class (with the noise of the base Object class removed)

<ClassName>.public_instance_methods - Object.public_instance_methods

Showing what classes a given class inherits from

<ClassName>.ancestors

using Class.constants you can get a list of contants provided by the class.

Resources and Links

General

Gem to wrap cron

Ruby switcher Easy switching of various ruby versions on a single host.

Ruby & Shoes tutorial

Ruby and bcrypt

Useful list of regular expressions for things like IP addresses.

command line app. skeleton Notes on setting up a basic command-line application skeleton with usage and options parsing

pleac ruby file examples Many example of ruby file usage

Mail Gem

Ruby Backup Class

meanings for the $ GLOBALS

Getting Started with Nokogiri

Makeing ruby 1.9.1 default on Ubuntu

Rorys Ruby Idioms

Tutorial on Ruby File and Directory Handling

Rack

Loads of rack resources

rack enabling classes with rackable