irb

Start the interactive shell

$ irb

irb [options] [--] [programfile] [arguments]…

--help
    Display help message

--version
    Print IRB version

-r LIBRARY, --require LIBRARY
    Require Ruby library before starting

--prompt-mode MODE
    Set prompt mode (default, simple, inf-ruby, xmp, null)

--readline
    Enable Readline for completion and history

--noprompt
    Disable prompt display

--noinspect
    Disable inspect method for output

--inspect
    Enable inspect for output (default)

--noscript
    Disable script trace output

--tracer
    Enable automatic trace

--back-trace-limit N
    Set backtrace limit (default: 16)

--verbose
    Enable verbose output

-d, --debug
    Set debug level (equivalent to --debug-level 2)

--inf-ruby-mode
    Load inf-ruby-mode for Emacs

--sample-book
    Load sample book as initial program

IRB (Interactive RuBy) is a REPL (Read-Eval-Print Loop) tool for the Ruby programming language, providing an interactive environment to execute Ruby code line-by-line from the terminal. Ideal for prototyping, debugging, testing expressions, and learning Ruby, it evaluates input immediately and displays results with inspect formatting.

Key features include multiline editing, command history (with Readline support), exception backtraces, variable inspection via @ or binding.irb, and customizable prompts. Start with irb to enter the shell; type exit or quit to leave. Load libraries with -r, run scripts non-interactively, or embed in Ruby programs.

IRB supports prompt modes like default (>>), simple (%), and inf-ruby for Emacs integration. It's essential for Rubyists, enhancing development workflow alongside tools like pry or byebug. Available on any system with Ruby installed.

Requires Ruby installation; behavior depends on Ruby version. Readline may need libreadline-dev. Non-interactive mode exits after script.

Customizable prompts:
• default: >> (primary), ? (secondary)
• simple: % >>, %?
• inf-ruby: INF-RUBY >>, INF-RUBY ?
• xmp: ==>
• null: no prompt

Embed in Ruby scripts:
require 'irb'
IRB.start
Or use binding.irb for contextual debugging.

Developed by Keiju Ishitsuka, IRB debuted in Ruby 1.6 (2000) as Ruby's first interactive shell. Evolved with Ruby releases, adding features like multiline support in 1.8+ and better readline in 1.9+. Now integral to modern Ruby (3.x+).

ruby(1), ri(1), rdoc(1), gem(1), pry(1)