ri - Man Page

Ruby API reference front end


ri[-ahilTv] [-d DIRNAME] [-f FORMAT] [-w WIDTH] [--[no-]pager] [--server[=PORT]] [--[no-]list-doc-dirs] [--no-standard-docs] [--[no-]{system|site|gems|home}] [--[no-]profile] [--dump=CACHE] [name ...]


ri is a command-line front end for the Ruby API reference. You can search and read the API reference for classes and methods with ri.

ri is a part of Ruby.

name can be:

Class | Module | Module::Class
Class::method | Class#method | Class.method | method
gem_name: | gem_name:README | gem_name:History

All class names may be abbreviated to their minimum unambiguous form. If a name is ambiguous, all valid options will be listed.

A ‘.’ matches either class or instance methods, while #method matches only instance and ::method matches only class methods.

README and other files may be displayed by prefixing them with the gem name they're contained in. If the gem name is followed by a ‘:’ all files in the gem will be shown. The file name extension may be omitted where it is unambiguous.

For example:

ri Fil
ri File
ri File.new
ri zip
ri rdoc:README

Note that shell quoting or escaping may be required for method names containing punctuation:

ri 'Array.[]'
ri compact\!

To see the default directories ri will search, run:

ri --list-doc-dirs

Specifying the --system, --site, --home, --gems, or --doc-dir options will limit ri to searching only the specified directories.

ri options may be set in the RI environment variable.

The ri pager can be set with the RI_PAGER environment variable or the PAGER environment variable.



In interactive mode you can repeatedly look up methods with autocomplete.


Show all documentation for a class or module.


List classes ri knows about.


Send output to a pager, rather than directly to stdout.


Synonym for --no-pager.


Set the width of the output.


Run RDoc server on the given port. The default port is 8214.


Use the selected formatter. The default formatter is bs for paged output and ansi otherwise. Valid formatters are: ansi, bs, markdown, rdoc.


Show help and exit.


Output version information and exit.

Data source options:


List the directories from which ri will source documentation on stdout and exit.


List of directories from which to source documentation in addition to the standard directories. May be repeated.


Do not include documentation from the Ruby standard library, site_lib, installed gems, or ~/.rdoc. Use with --doc-dir.


Include documentation from Ruby's standard library. Defaults to true.


Include documentation from libraries installed in site_lib. Defaults to true.


Include documentation from RubyGems. Defaults to true.


Include documentation stored in ~/.rdoc. Defaults to true.

Debug options:


Run with the Ruby profiler.


Dump data from an ri cache or data file.



Options to prepend to those specified on the command-line.


Pager program to use for displaying.


Path to the user's home directory.



Path for ri data in the user's home directory.

See Also

ruby(1), rdoc(1), gem(1)

Reporting Bugs


Written by Dave Thomas ⟨dave@pragmaticprogrammer.com⟩.

Referenced By


April 20, 2017