Fixing Ruby pry/readline under Ubuntu

Disclaimer: I don’t know why this error occurred on my office installation of Ubuntu 10.04 but this is what I did to solve it.

After installing pry (with a RVM ruby version) and wanting to run it I got the following error block:

mallibone@troulwd0062:~$ pry
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_HOOKS
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_PRINT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant SIMPLE_PRINT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant CLIPPED_PRINT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_EXCEPTION_HANDLER
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_EXCEPTION_WHITELIST
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_PROMPT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant SIMPLE_PROMPT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant SHELL_PROMPT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant NAV_PROMPT
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_CONTROL_D_HANDLER
/home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- warning: already initialized constant DEFAULT_SYSTEM
/home/users/mallibone/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- readline (LoadError)
        from /home/users/mallibone/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
        from /home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- `'
        from /home/users/mallibone/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
        from /home/users/mallibone/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
        from /home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- `rescue in '
        from /home/users/mallibone/.rvm/gems/ruby-1.9.3-p125@global/gems/pry- `'
        from /home/users/mallibone/.rvm/gems/ruby-1.9.3-p125/bin/pry:19:in `load'
        from /home/users/mallibone/.rvm/gems/ruby-1.9.3-p125/bin/pry:19:in `'

Now the line that shows us the error is this one:

/home/users/mallibone/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- readline (LoadError)

So we have a readline error. No need to click onto that link and go off reading just keep in mind that this library does the following:

The GNU Readline library provides a set of functions for use by applications that allow users to edit command lines as they are typed in.

But back to the original problem, how do we get it running? Well in your Ruby installation there is a extconf.rb file which according to the read-me: The Readline module provides interface for GNU Readline.. So what we have to do now is update our installation i.e. update this wrapper module. I’m using RVM so I found the file under the path[1]:


To update our wrapper cd into your readline directory and run the following commands:

ruby extconf.rb
sudo make install

The typing pry into the shell resulted in the rewarding response:

[1] pry(main)>


Under Ubuntu 11.10 you have to further install libreadline library to get pry and AFAIK the rails console. One way to do this is by the following lines (again using RVM):

rvm uninstall 1.9.3-p125
sudo apt-get install libreadline-dev
rvm install 1.9.3-p125 --with-readline-dir=/usr/include/readline

Thank you megas for pointing out this issue under Ubuntu 11.10 and providing a good explanation and solution to the problem.


Readline LoadError Solution
GNU Readline

[1] If you don’t know where or what kind of installation you have type cd / into your command line and then

find . -name "extconf.rb"

This should show you where your extconf.rb file is but may take a while looking for it.

8 Responses to Fixing Ruby pry/readline under Ubuntu

  1. megas says:

    After I typed ‘make’ command it answered: make: Nothing to be done for `all’. How to fix it?

    • mallibone says:

      @megas you can force make to recompile (it’s telling you that your current binary is current) by typing ‘make -B’

      • megas says:

        The same answer. Maybe the problem started from extconf.rb, on command ‘ruby extconf.rb’ it showed:
        checking for tgetnum() in -lncurses… yes
        checking for readline/readline.h… no
        checking for editline/readline.h… no
        Is this message correct?

      • mallibone says:

        How did you install your Ruby env? With RVM? I.e. does your user have write permissions in the ruby env directory? Have you tried ‘make clean’? If all this doesn’t help you might want to try your luck on (will have a look at the more detailed question if you give me the link)

    • mallibone says:

      Hey @megas sorry for having you go to SO, but after googling your second comment I figured you might be missing libncurses. Try:

      sudo apt-get install libncurses5-dev libreadline5-dev

      Found it on this blog.

  2. Noah says:

    Thank you so much for this! I would have had a heck of a time figuring out how to get pry running on my own.

  3. Matt says:

    Great write up! It may be worth mentioning that I had to perform the steps in the Update section even though I am running 10.10. Thanks a lot for this!

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