Debugger

1. The first kind of line-by-line ruby debugging tool is called irb. The call of irb be made by command line, by the command:

 irb script_name.rb

2. Ruby has also a “pure ruby” debugger built right in. To use it:

 ruby -rdebug script_name.rb

or

 require 'debug' #somewhere in your script

If you’re on MRI, it is probably far recommended to use ruby-debug gem (which is in C, so faster), or, on 1.9, ruby-debug19 gem (same as ruby-debug gem, but written for 1.9). See a list of differences.

3. However, another options are available: a common alternative involves the optional gem "pry". Also in this case, the file to be debugged need the require instruction at the file top.