Skip to content

FAQ

Jump to bottom Edit New page
André Luis Leal Cardoso Junior edited this page Mar 12, 2022 · 77 revisions

Quick Menu:

Back to Main Menu

How can I use awesome_print with Pry?

If you miss awesome_print's way of formatting output, here's how you can use it in place of the formatting which comes with pry.

Append this code to .pryrc.

begin
  require 'awesome_print'
  Pry.config.print = proc { |output, value| output.puts value.ai }
rescue LoadError => err
  puts "no awesome_print :("
end

If you would like to use Pry's pager with awesome_print a slight modification to the above is needed:

begin
  require 'awesome_print'
  Pry.config.print = proc { |output, value| Pry::Helpers::BaseHelpers.stagger_output("=> #{value.ai}", output) }
rescue LoadError => err
  puts "no awesome_print :("
end

Threads don't work, what's wrong?

Some systems (Mac OS X in particular) use Editline instead of GNU Readline. The Ruby Readline library currently has an issue when compiled with the Editline library which makes it block all threads rather than just the one calling Readline.readline() (it blocks while holding the global VM lock, preventing other threads from acquiring it). This can be fixed by installing [GNU Readline on OS X] (https://github.com/guard/guard/wiki/Add-Readline-support-to-Ruby-on-Mac-OS-X).

An alternative is using https://github.com/luislavena/rb-readline, a pure-Ruby implementation of Readline that does not suffer the threading issue, though this has other issues.

How can I get readline support (ctrl+r etc) for Pry in OSX?

Technically for OSX you don't need readline, and we'll focus on using libedit which OSX comes with instead.

Edit the file .editrc in your home directory. Add this line:

bind "^R" em-inc-search-prev

You can now use ctrl+r to do a reverse history search.

Ref: http://hints.macworld.com/article.php?story=20080313113705760

Alternatively, install GNU Readline and get Ruby to use it: https://github.com/guard/guard/wiki/Add-Readline-support-to-Ruby-on-Mac-OS-X

Finally, Pry does work with rb-readline, a pure Ruby implementation of Readline which shouldn't suffer from the platform and install dependencies of the standard Readline. Ref: https://github.com/luislavena/rb-readline

How do I clear the screen in a Pry session?

You can either use ^L (control-l) or use Pry's shell integration features to accomplish this:

In *nix systems:

pry(main)> .clear

In Windows systems:

pry(main)> .cls

How can I use the Hirb gem with Pry?

To use Hirb with Pry add the following code to your .pryrc file:

begin
  require 'hirb'
rescue LoadError
  # Missing goodies, bummer
end

if defined? Hirb
  # Slightly dirty hack to fully support in-session Hirb.disable/enable toggling
  Hirb::View.instance_eval do
    def enable_output_method
      @output_method = true
      @old_print = Pry.config.print
      Pry.config.print = proc do |*args|
        Hirb::View.view_or_page_output(args[1]) || @old_print.call(*args)
      end
    end

    def disable_output_method
      Pry.config.print = @old_print
      @output_method = nil
    end
  end

  Hirb.enable
end

If you'd rather not have a monkey patch to maintain, the following will work as well, without the ability to disable Hirb during a session:

require 'hirb'

Hirb.enable

old_print = Pry.config.print
Pry.config.print = proc do |*args|
  Hirb::View.view_or_page_output(args[1]) || old_print.call(*args)
end

How can I use Pry with pow?

Pry now supports remote sessions with the pry-remote gem.

After installing pry-remote and requiring it in your code simply use binding.remote_pry (instead of the usual binding.pry) and connect to the session from another terminal using pry-remote. See the pry-remote project page for more information.

Back to top

Why is ~ printed when I type the delete key?

Regular OS X Terminal

  • Go to Terminal > Preferences > Settings > Keyboard
  • Click Forward Delete
  • Select Send String to Shell
  • Press CTRL + ALT + d
  • You want to see \004

iTerm2

  • Go to iTerm > Preferences... > Keys
  • Add a Global Shortcut Key
  • Type the delete key as Shortcut (NOTE: this requires typing fn+delete on mac keyboards).
  • Select Send Hex Codes as Action and type 0x004
  • Click on OK and you're good to go

iTerm

Take a look at this article (works for Lion too, but you should use iTerm2).

Build ruby with readline

(can somebody confirm this for iTerm too?) The solution proposed for the regular OS X Terminal might have the side effect that your delete key will issue CTRL + d (same as when you type exit) when there is nothing on the current line.

Ruby on OS X will use libedit instead of libreadline by default. Building Ruby with readline usually solves the problem. The obvious downside of this solution is that you might have to reinstall your gems. For rbenv/ruby-build you can use something like this:

brew install readline && CONFIGURE_OPTS="--with-readline-dir=$(brew --prefix readline)" rbenv install <your version, e.g: 1.9.3-p194>

Why is my emacs shell output showing odd characters?

If you run pry within Emacs' M-x shell and see output similar to this

$ pry
input>
[1A[0Ginput> [1B[0Ginput>

There are ansi codes embedded in the auto_indent that emacs' shell does not render properly. To clean this up add the following to your .pryrc

Pry.config.auto_indent = false

Back to top

What if the output of a line is going to dump a huge object?

Make a ; the last char on the line, and that line will output nothing.

Back to top

How can I ignore commands on incompleted lines?

An example is:

[1] pry(main)> class Example1
[1] pry(main)*   def exit
[1] pry(main)*     exit

In this example, the Pry command exit is being called, not the Ruby one. Such precedence of Pry commands over Ruby (when in conflict) preserves the functionality of commands like edit, amend-line, play, and even show-source, which are pretty cool.

  1. Prefix a semicolon (or space) before you type the line
  2. Disable the annoying commands (Pry.commands.delete 'exit') in your ~/.pryrc
  3. Rename the annoying commands (Pry.commands.rename_command '%exit', 'exit')
  4. Use a Pry.config.command_prefix
  5. Turn on command collision warnings (Pry.config.collision_warnings = true)

Back to top

Does Pry have an easy way to copy to clipboard instead of to Gist?

Yes, via the pry-jist gem. There is gist --clip command (aliased to clipit).

Given a class:

class Foo
  def bar
    :bar
  end
end
pry(main)> clipit Foo#bar
Copied content to clipboard!

You can also copy the whole class

pry(main)> clipit Foo
Copied content to clipboard!

Back to top

Why doesn't Pry work with Ruby 1.9.1?

Ruby 1.9.1 is not supported. The way that class_eval and instance_eval works in 1.9.1 is anomalous and different to anything in 1.8 or 1.9.2 and higher. Try to upgrade your Ruby to 1.9.3.

Link for curious people: Ruby 1.9.1: uninitialized constant Pry::CommandSet::Ls (NameError)

Back to top

How do I stop executing a binding.pry call in a loop?

Let's consider the following example.

def magic_loop
  5.times do |i|
    puts "Iteration #{ i + 1 }"
    binding.pry
  end

  puts "Sorry, no more magic left for today!"
end

Pay attention to the line with binding.pry invocation. Let's run the code.

[2] pry(main)> magic_loop
Iteration 1

From: (pry) @ line 4 Object#magic_loop:

    1: def magic_loop
    2:   5.times do |i|
    3:     puts "Iteration #{ i + 1 }"
 => 4:     binding.pry
    5:   end
    6:
    7:   puts "Sorry, no more magic left for today!"
    8: end

[1] pry(main)> exit
Iteration 2

From: (pry) @ line 4 Object#magic_loop:

    1: def magic_loop
    2:   5.times do |i|
    3:     puts "Iteration #{ i + 1 }"
 => 4:     binding.pry
    5:   end
    6:
    7:   puts "Sorry, no more magic left for today!"
    8: end

[1] pry(main)> exit
Iteration 3

From: (pry) @ line 4 Object#magic_loop:

    1: def magic_loop
    2:   5.times do |i|
    3:     puts "Iteration #{ i + 1 }"
 => 4:     binding.pry
    5:   end
    6:
    7:   puts "Sorry, no more magic left for today!"
    8: end

Meh, I cannot exit the loop quickly. I have to type exit (or press ^D) 5 times! Keep calm, because there is a simple solution.

The raise-up command will raise an exception to the containing pry instance (RuntimeError if you give it no arguments.) Simply type raise-up and find yourself out of the loop. It also works if you want to raise an exception that will not be caught without terminating the entire REPL (as in RSpec.)

Alternatively, you can use the disable-pry command.

[1] pry(main)> disable-pry
Iteration 4
Iteration 5
Sorry, no more magic left for today!
=> nil
[3] pry(main)>

Great! Check the description of the command with help disable-pry. Now, let's try to run the method one more time.

[3] pry(main)> magic_loop
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
Sorry, no more magic left for today!
=> nil
[4] pry(main)>

Wait, what? How do I re-enable Pry? Although there is no enable-pry command in Pry, there is an easy way to add it: you can roll up your own command. Add this to your ~/.pryrc.

# ~/.pryrc
Pry::Commands.block_command('enable-pry', 'Enable `binding.pry` feature') do
  ENV['DISABLE_PRY'] = nil
end

Now, just execute the freshly added command and try to run magic_loop again.

Web developers may find it useful to simply call ENV['DISABLE_PRY'] = nil before every request, in a before_filter or whatever their framework of choice provides. As it is just an environment variable, it will not risk breaking anything.

There is a faster but blunt way to exit a loop containing pry calls; exit the process by running Process.exit. Note that your ruby instance will be terminated and you will lose any unsaved data.

Back to top

How do I use other pager than less?

Just set the PAGER environment variable. For example:

% PAGER="my-pager" pry
[1] pry(main)>

Back to top

How do I use less on Windows?

The default native pager on Windows may not be nice to use over the long term, but you can install and run less natively on Windows without much fuss.

The easiest way is through the chocolatey package manager. After chocolatey is installed, you can install less with the following command from an Administrator terminal:

choco install less

Then start Pry and less will be the default pager. Enjoy :)

Back to top

binding.pry is a function of the pry-rails gem, yeah?

Nope. It's a part of Pry. If you want to learn more about it, read the article called So what is “binding.pry” exactly.

Back to top

Add a custom footer
Add a custom sidebar
Clone this wiki locally