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Sushant Bajracharya
Sushant Bajracharya

Posted on • Edited on

Debugging with IEx

#elixir

There are already too many articles about Debugging with IEx on the web, so I will just get to the point straight.

FYI: As per Jose, Pry is not a debugger. It just allows you to interact with a particular context. https://stackoverflow.com/questions/33203676/iex-pry-going-step-by-step

If you want to

add a breakpoint in your code: require IEx; IEx.pry()

continue to the next breakpoint: continue()

continue the execution of code without hitting any other breakpoints: respawn()

add a breakpoint to a function: IEx.break!(Module, :function, arity) eg IEx.break!(String, :length, 1)

know your breakpoints current location: whereami

open the code in the editor: open()

list out all the methods of a module: exports(ModuleName)

Keep In Mind, that

  • helper functions like continue, respawn, whereami are only available inside pry session.

  • whereami, open won't work with precompiled source code

  • You need to configure either ELIXIR_EDITOR or EDITOR env variable for open to work

Productivity

It would make your life easier if you would configure a couple of things.

  • Enabling History

If you want to have access to the commands you typed in your previous iex session, then add this export ERL_AFLAGS="-kernel shell_history enabled" to your .bashrc file and source .bashrc. You won't get your shell history if you had terminated the previous IEx session by pressing Ctrl + c two times. The right way to exit IEx session is to ctrl g + q

  • Customizing your IEx

You can customize your IEx by creating .iex.exs file. This file gets executed every time you run IEx.

My .iex.exs file:

IO.puts """ ` ;: `+; ++', .+++, :'++'. .+'++'; Welcome to elixir-land ,+'+''': `:+'+';';; http://elixir-lang.org ,:++';;;;'. http://www.phoenixframework.org/ ::'+';;;;'' https://hex.pm/ :;;++;;';'' http://www.elixirschool.com/ .;;'''';;;: https://github.com/christopheradams/elixir_style_guide ,:::'';,,. ,,,,,:::, ,,,,,,, ``.` """ IEx.configure( alive_prompt: "%prefix(%node):%counter>", default_prompt: "%prefix:%counter>", inspect: [pretty: true, char_lists: :as_lists, limit: :infinity], history_size: -1, colors: [ ls_directory: :cyan, ls_device: :yellow, doc_code: :green, doc_inline_code: :magenta, doc_headings: [:cyan, :underline], doc_title: [:cyan, :bright, :underline], eval_result: [ :cyan, :bright ] ] ) import_file_if_available(".secret.exs") rs = fn -> Process.exit(self(), :normal) end

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