Pry and debugger cheat sheet

pry_and_debugger_cheat_sheet.md

Ruby Debugging

Pry

ruby -rpry some_script.rb - the r means require. If there's a binding.pry there, you'll be on it.

Pry gives you a graphical look at your program in progress, lets you cd among objects, ls to see available variables, etc. You can't step, though; just explore a snapshot at that moment.

Debugger

Must install debugger gem for your version of Ruby (1.9 is 'gem install debugger'). Doesn't play well with Spork.

rspec some_test_spec.rb --debug will stop on a debugger statement.

In a debugging session, set autolist on says "keep showing me graphically where I am."

• l shows lines of code forward. Has flags:
  • - backward
  • = current line
  • X-Y lines X to Y
• n is for "next"; "step over"
• s is for "step"; "step into"
• e some_statement evaluates that. If you want to do more, irb drops you into it.
• hitting enter re-executes the last command; if you hit n and want to keep stepping, hit enter.
• l18 displays line 18
• Breakpoints
  • b file:line [if expr] sets a breakpoint
  • b class(.|#)method [if expr] sets a breakpoint
  • del [nnn] deletes some or all breakpoints
• Displaying expressions
  • disp [expression] shows value of expression at every step
  • undisp [nnn] cancels display options
• Examining the call stack
  • May have to call Debugger.start first?
    • where, up, down, frame
    • bashd.sourceforge.net/ruby-debug.html#FrameCommands
• help is available

Debugger configuration

Put a .rdebugrc in the project directory or your home directory with:

set autolist
set autoeval
set autoreload

Cool summary, however you can step with pry if you install the pry-debugger plugin, you can also engage in even more sophisticated types of debugging if you install the pry-rescue plugin. For a fuller look at pry plugins available, check out https://github.com/pry/pry/wiki/Available-plugins and the Pry Ecosystem posts.

updated cheat sheet for pry https://gist.github.com/lfender6445/9919357