The Book of Ruby

Debugging

The default Ruby debugger allows you to set breakpoints and watchpoints and evaluate variables while your programs execute. To run a program in the debugger, use the -r debug option (where -r means “require” and debug is the name of the debugging library) when you start the Ruby interpreter. For example, this is how you would debug a program called debug_test.rb:

ruby -r debug  debug_test.rb

Once the debugger has started, you can enter various commands to step through your code, set breakpoints to cause the execution to pause at specific lines, set watches to monitor the values of variables, and so on. The following are the available debugging commands:

b[reak] [file|class:]<line|method> and b[reak] [file|class:]<line|method>

Sets breakpoint ...