![]() We put a conditional around tests so that we skip those those using show-source (namely the one in run_command_spec.rb) on ree/ruby18 |
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pry.gemspec |
README.markdown
© John Mair (banisterfiend) 2012
Please DONATE to the Pry project - Pry was a huge amount of work and every donation received is encouraging and supports Pry's continued development!
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Other Resources
Skip to the website (recommended)
Skip to the wiki
Pry is a powerful alternative to the standard IRB shell for Ruby. It is written from scratch to provide a number of advanced features, including:
-
Source code browsing (including core C source with the pry-doc gem)
-
Documentation browsing
-
Live help system
-
Open methods in editors (
edit-method Class#method
) -
Syntax highlighting
-
Command shell integration (start editors, run git, and rake from within Pry)
-
Gist integration
-
Navigation around state (
cd
,ls
and friends) -
Runtime invocation (use Pry as a developer console or debugger)
-
Exotic object support (BasicObject instances, IClasses, ...)
-
A Powerful and flexible command system
-
Ability to view and replay history
-
Many convenience commands inspired by IPython, Smalltalk and other advanced REPLs
-
A wide-range number of plugins that provide remote sessions, full debugging functionality, and more.
Pry also aims to be more than an IRB replacement; it is an attempt to bring REPL driven programming to the Ruby language. It is currently not as powerful as tools like SLIME for lisp, but that is the general direction Pry is heading.
Pry is also fairly flexible and allows significant user
customization
is trivial to set it to read from any object that has a readline
method and write to any object that has a
puts
method - many other aspects of Pry are also configurable making
it a good choice for implementing custom shells.
Pry comes with an executable so it can be invoked at the command line.
Just enter pry
to start. A .pryrc
file in the user's home directory will
be loaded if it exists. Type pry --help
at the command line for more
information.
Try gem install pry-doc
for additional documentation on Ruby Core
methods. The additional docs are accessed through the show-doc
and
show-method
commands.
- Install the gem:
gem install pry
- Browse the comprehensive documentation at the official Pry wiki
- Read the YARD API documentation
- See the source code
Pry also has rubygems-test
support; to participate, first install
Pry, then:
- Install rubygems-test:
gem install rubygems-test
- Run the test:
gem test pry
- Finally choose 'Yes' to upload the results.
Commands
Nearly every piece of functionality in a Pry session is implemented as a command. Commands are not methods and must start at the beginning of a line, with no whitespace in between. Commands support a flexible syntax and allow 'options' in the same way as shell commands, for example the following Pry command will show a list of all private instance methods (in scope) that begin with 'pa'
pry(YARD::Parser::SourceParser):5> ls -Mp --grep ^pa
YARD::Parser::SourceParser#methods: parse parser_class parser_type parser_type= parser_type_for_filename
Navigating around state
Pry allows us to pop in and out of different scopes (objects) using
the cd
command. This enables us to explore the run-time view of a
program or library. To view which variables and methods are available
within a particular scope we use the versatile ls command.
Here we will begin Pry at top-level, then Pry on a class and then on an instance variable inside that class:
pry(main)> class Hello
pry(main)* @x = 20
pry(main)* end
=> 20
pry(main)> cd Hello
pry(Hello):1> ls -i
instance variables: @x
pry(Hello):1> cd @x
pry(20:2)> self + 10
=> 30
pry(20:2)> cd ..
pry(Hello):1> cd ..
pry(main)> cd ..
The number after the :
in the pry prompt indicates the nesting
level. To display more information about nesting, use the nesting
command. E.g
pry("friend":3)> nesting
Nesting status:
0. main (Pry top level)
1. Hello
2. 100
3. "friend"
=> nil
We can then jump back to any of the previous nesting levels by using
the jump-to
command:
pry("friend":3)> jump-to 1
=> 100
pry(Hello):1>
Runtime invocation
Pry can be invoked in the middle of a running program. It opens a Pry
session at the point it's called and makes all program state at that
point available. It can be invoked on any object using the
my_object.pry
syntax or on the current binding (or any binding)
using binding.pry
. The Pry session will then begin within the scope
of the object (or binding). When the session ends the program continues with any
modifications you made to it.
This functionality can be used for such things as: debugging, implementing developer consoles and applying hot patches.
code:
# test.rb
require 'pry'
class A
def hello() puts "hello world!" end
end
a = A.new
# start a REPL session
binding.pry
# program resumes here (after pry session)
puts "program resumes here."
Pry session:
pry(main)> a.hello
hello world!
=> nil
pry(main)> def a.goodbye
pry(main)* puts "goodbye cruel world!"
pry(main)* end
=> nil
pry(main)> a.goodbye
goodbye cruel world!
=> nil
pry(main)> exit
program resumes here.
Command Shell Integration
A line of input that begins with a '.' will be forwarded to the command shell. This enables us to navigate the file system, spawn editors, and run git and rake directly from within Pry.
Further, we can use the shell-mode
command to incorporate the
present working directory into the Pry prompt and bring in (limited at this stage, sorry) file name completion.
We can also interpolate Ruby code directly into the shell by
using the normal #{}
string interpolation syntax.
In the code below we're going to switch to shell-mode
and edit the
.pryrc
file in the home directory. We'll then cat its contents and
reload the file.
pry(main)> shell-mode
pry main:/home/john/ruby/projects/pry $ .cd ~
pry main:/home/john $ .emacsclient .pryrc
pry main:/home/john $ .cat .pryrc
def hello_world
puts "hello world!"
end
pry main:/home/john $ load ".pryrc"
=> true
pry main:/home/john $ hello_world
hello world!
We can also interpolate Ruby code into the shell. In the
example below we use the shell command cat
on a random file from the
current directory and count the number of lines in that file with
wc
:
pry main:/home/john $ .cat #{Dir['*.*'].sample} | wc -l
44
Code Browsing
You can browse method source code with the show-method
command. Nearly all Ruby methods (and some C methods, with the pry-doc
gem) can have their source viewed. Code that is longer than a page is
sent through a pager (such as less), and all code is properly syntax
highlighted (even C code).
The show-method
command accepts two syntaxes, the typical ri
Class#method
syntax and also simply the name of a method that's in
scope. You can optionally pass the -l
option to show-method to
include line numbers in the output.
In the following example we will enter the Pry
class, list the
instance methods beginning with 're' and display the source code for the rep
method:
pry(main)> cd Pry
pry(Pry)> ls -M --grep re
Pry#methods: re readline refresh rep repl repl_epilogue repl_prologue retrieve_line
pry(Pry):1> show-method rep -l
From: /home/john/ruby/projects/pry/lib/pry/pry_instance.rb @ line 143:
Number of lines: 6
143: def rep(target=TOPLEVEL_BINDING)
144: target = Pry.binding_for(target)
145: result = re(target)
146:
147: show_result(result) if should_print?
148: end
Note that we can also view C methods (from Ruby Core) using the
pry-doc
plugin; we also show off the alternate syntax for
show-method
:
pry(main)> show-method Array#select
From: array.c in Ruby Core (C Method):
Number of lines: 15
static VALUE
rb_ary_select(VALUE ary)
{
VALUE result;
long i;
RETURN_ENUMERATOR(ary, 0, 0);
result = rb_ary_new2(RARRAY_LEN(ary));
for (i = 0; i < RARRAY_LEN(ary); i++) {
if (RTEST(rb_yield(RARRAY_PTR(ary)[i]))) {
rb_ary_push(result, rb_ary_elt(ary, i));
}
}
return result;
}
Documentation Browsing
One use-case for Pry is to explore a program at run-time by cd
-ing
in and out of objects and viewing and invoking methods. In the course
of exploring it may be useful to read the documentation for a
specific method that you come across. Like show-method
the show-doc
command supports
two syntaxes - the normal ri
syntax as well as accepting the name of
any method that is currently in scope.
The Pry documentation system does not rely on pre-generated rdoc
or
ri
, instead it grabs the comments directly above the method on
demand. This results in speedier documentation retrieval and allows
the Pry system to retrieve documentation for methods that would not be
picked up by rdoc
. Pry also has a basic understanding of both the
rdoc and yard formats and will attempt to syntax highlight the
documentation appropriately.
Nonetheless, the ri
functionality is very good and
has an advantage over Pry's system in that it allows documentation
lookup for classes as well as methods. Pry therefore has good
integration with ri
through the ri
command. The syntax
for the command is exactly as it would be in command-line -
so it is not necessary to quote strings.
In our example we will enter the Gem
class and view the
documentation for the try_activate
method:
pry(main)> cd Gem
pry(Gem):1> show-doc try_activate
From: /Users/john/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems.rb @ line 201:
Number of lines: 3
Try to activate a gem containing path. Returns true if
activation succeeded or wasn't needed because it was already
activated. Returns false if it can't find the path in a gem.
pry(Gem):1>
We can also use ri
in the normal way:
pry(main) ri Array#each
----------------------------------------------------------- Array#each
array.each {|item| block } -> array
------------------------------------------------------------------------
Calls _block_ once for each element in _self_, passing that element
as a parameter.
a = [ "a", "b", "c" ]
a.each {|x| print x, " -- " }
produces:
a -- b -- c --
Gist integration
If the gist
gem is installed then method source or documentation can be gisted to github with the
gist
command. The gist
command is capable of gisting almost any REPL content, including methods, documentation,
input expressions, command source, and so on. In the example below we will gist the C source
code for the Symbol#to_proc
method to github:
pry(main)> gist -m Symbol#to_proc
Gist created at https://gist.github.com/5332c38afc46d902ce46 and added to clipboard.
pry(main)>
You can see the actual gist generated here: https://gist.github.com/5332c38afc46d902ce46
Edit methods
You can use edit-method Class#method
or edit-method my_method
(if the method is in scope) to open a method for editing directly in
your favorite editor. Pry has knowledge of a few different editors and
will attempt to open the file at the line the method is defined.
You can set the editor to use by assigning to the Pry.editor
accessor. Pry.editor
will default to $EDITOR
or failing that will
use nano
as the backup default. The file that is edited will be
automatically reloaded after exiting the editor - reloading can be
suppressed by passing the --no-reload
option to edit-method
In the example below we will set our default editor to "emacsclient"
and open the Pry#repl
method for editing:
pry(main)> Pry.editor = "emacsclient"
pry(main)> edit-method Pry#repl
Live Help System
Many other commands are available in Pry; to see the full list type
help
at the prompt. A short description of each command is provided
with basic instructions for use; some commands have a more extensive
help that can be accessed via typing command_name --help
. A command
will typically say in its description if the --help
option is
avaiable.
Use Pry as your Rails Console
pry -r ./config/environment
MyArtChannel has kindly provided a hack to replace the rails console
command in Rails 3: https://gist.github.com/941174 This is not recommended for code bases with multiple developers, as they may not all want to use Pry.
Also check out the wiki for other strategies on integrating Pry with rails, notably the pry-rails plugin.
Limitations:
- Tab completion is currently a bit broken/limited this will have a major overhaul in a future version.
Syntax Highlighting
Syntax highlighting is on by default in Pry. You can toggle it on and
off in a session by using the toggle-color
command. Alternatively,
you can turn it off permanently by putting the line Pry.color = false
in your ~/.pryrc
file.
Future Directions
Many new features are planned such as:
- Increase modularity (rely more on plugin system)
- Much improved tab completion (using Bond)
- Much improved documentation system, better support for YARD
- Better support for code and method reloading and saving code
- Extended and more sophisticated command system, allowing piping between commands and running commands in background
Contact
Problems or questions? file an issue at github
Contributors
Pry is primarily the work of John Mair (banisterfiend), for full list of contributors see the CONTRIBUTORS file.