Ruby debug

What Ruby debug is

Ruby debug is an open-source debugger for Ruby MRI 2.7 and later. Its console lets developers evaluate Ruby expressions, examine program state, control execution, set conditional or exception breakpoints, and enable tracing. It can record a program’s execution and replay it by stepping backward through the log. The `rdbg` command can start Ruby scripts and commands such as Rails, Rake, and RSpec under the debugger, while a console can also attach to a running program over a UNIX domain socket or TCP/IP.

For an interactive console, Ruby debug can use IRB, with autocompletion, multiline input, and commands including `show_source` and `show_doc`. The project describes frontends for VS Code and Chrome DevTools; VS Code use requires the vscode-rdbg extension. Install the gem with `gem install debug` or add `gem "debug", ">= 1.0.0"` to a Gemfile. The project says it has no performance penalty when it is not stepping and no breakpoints are set. The free gem is licensed under BSD-2-Clause. The project describes the debugger as not mature, and warns that remote messages are unencrypted and that `debug/open_nonstop` can expose debugging access without stopping the program.

Who it suits

Ruby MRI developers who need to inspect execution, set breakpoints, trace, or step backward through a recorded run may find Ruby debug useful. It also suits developers who want to launch Ruby scripts or Rails, Rake, and RSpec commands with `rdbg`, or connect a console to a running program.

Getting started

1. Open https://github.com/ruby/debug.
2. Install with `gem install debug` or add `gem "debug", ">= 1.0.0"` to a Gemfile.
3. Use `rdbg` to launch a Ruby script or a Rails, Rake, or RSpec command.
4. For VS Code, use the vscode-rdbg extension.

Verdict

Choose Ruby debug if you work with Ruby MRI 2.7 or later and want a debugger with breakpoints, remote attachment, and backward replay. Look elsewhere if the project’s stated maturity caveat or its remote-access security warnings do not fit your needs.