Byebug
Debugging in Ruby 2
Byebug is a simple to use, feature rich debugger for Ruby 2. It uses the new
TracePoint API for execution control and the new Debug Inspector API for call
stack navigation, so it doesn’t depend on internal core sources. It’s developed
as a C extension, so it’s fast. And it has a full test suite so it’s reliable.
It allows you to see what is going on inside a Ruby program while it executes
and offers many of the traditional debugging features such as:
- Stepping: Running your program one line at a time.
- Breaking: Pausing the program at some event or specified instruction, to examine the current state.
- Evaluating: Basic REPL functionality, although pry does a better job at that.
- Tracking: Keeping track of the different values of your variables or the different lines executed by your program.
Build Status
Linux & OSX 
Windows
Requirements
Required: MRI 2.0.0 or higher. For debugging ruby 1.9.3 or older, use
debugger.Recommended:
- MRI 2.0.0-p576 or higher.
- MRI 2.1.3 or higher.
- MRI 2.2.1 or higher.
Install
$ gem install byebug
Usage
Simply drop
byebug
wherever you want to start debugging and the execution will stop there. If you
are debugging rails, start the server and once the execution gets to your
byebug command you will get a debugging prompt.
Byebug’s commands
| Command | Aliases | Subcommands |
|---|---|---|
backtrace |
bt where |
|
break |
||
catch |
||
condition |
||
continue |
||
delete |
||
disable |
breakpoints display |
|
display |
||
down |
||
edit |
||
enable |
breakpoints display |
|
eval |
||
finish |
||
frame |
||
help |
||
history |
||
info |
args breakpoints catch display file files line program |
|
irb |
||
kill |
||
list |
||
method |
instance |
|
next |
||
pp |
||
pry |
||
ps |
||
putl |
||
quit |
exit |
|
restart |
||
save |
||
set |
autoeval autoirb autolist autosave basename callstyle fullpath histfile histsize linetrace listsize post_mortem stack_on_error verbose width |
|
show |
autoeval autoirb autolist autosave basename callstyle fullpath histfile histsize linetrace listsize post_mortem stack_on_error verbose width |
|
source |
||
step |
||
thread |
current list resume stop switch |
|
tracevar |
||
undisplay |
||
up |
||
var |
all constant global instance local |
Semantic Versioning
Byebug tries to follow semantic versioning and tries to
bump major version only when backwards incompatible changes are released.
Backwards compatibility is targeted to pry-byebug and any other plugins
relying on byebug.
Getting Started
Read byebug’s markdown
guide to get
started. Proper documentation will be eventually written.
Related projects
- pry-byebug adds
next,step,finish,continueandbreakcommands topryusingbyebug. - ruby-debug-passenger adds a rake task that restarts Passenger with Byebug connected.
- minitest-byebug starts a byebug session on minitest failures.
- sublime_debugger provides a plugin for ruby debugging on Sublime Text.
Contribute
See Getting Started with Development.
Credits
Everybody who has ever contributed to this forked and reforked piece of
software, specially: