Outputs a source level execution trace of a Ruby program.

It does this by registering an event handler with Kernel#set_trace_func for processing incoming events. It also provides methods for filtering unwanted trace output (see Tracer.add_filter, Tracer.on, and Tracer.off).

Add this line to your application's Gemfile:

gem 'tracer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install tracer

Consider the following Ruby script

  class A
    def square(a)
      return a*a
    end
  end

  a = A.new
  a.square(5)

Running the above script using ruby -r tracer example.rb will output the following trace to STDOUT (Note you can also explicitly require 'tracer')

  #0:<internal:lib/rubygems/custom_require>:38:Kernel:<: -
  #0:example.rb:3::-: class A
  #0:example.rb:3::C: class A
  #0:example.rb:4::-:   def square(a)
  #0:example.rb:7::E: end
  #0:example.rb:9::-: a = A.new
  #0:example.rb:10::-: a.square(5)
  #0:example.rb:4:A:>:   def square(a)
  #0:example.rb:5:A:-:     return a*a
  #0:example.rb:6:A:<:   end
   |  |         | |  |
   |  |         | |   ---------------------+ event
   |  |         |  ------------------------+ class
   |  |          --------------------------+ line
   |   ------------------------------------+ filename
    ---------------------------------------+ thread

Symbol table used for displaying incoming events:

+}+:: call a C-language routine
+{+:: return from a C-language routine
+>+:: call a Ruby method
+C+:: start a class or module definition
+E+:: finish a class or module definition
+-+:: execute code on a new line
+^+:: raise an exception
+<+:: return from a Ruby method

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/tracer.

The gem is available as open source under the terms of the 2-Clause BSD License.