[erlang-questions] Debugging apps with dependencies

Tristan Sloughter <>
Mon Apr 30 20:48:12 CEST 2012

Correct about why you can't find appmon, but there is an easy way around
this. Start the release yourself, you probably have to add your libs to
ERL_LIBS first depending how how you have things setup. So like:

$ export ERL_LIBS=$ERL_LIBS:<path to dir with your compiled apps>
$ erl -boot <path to boot file>

This will have your release running in your main erts env, not one created
specifically for your release.

Someone else can probably give better instructions based on where rebar
places the libs and .boot file, I don't know those.


On Mon, Apr 30, 2012 at 1:05 PM, Josh Black <> wrote:

> Hi, erlang beginner here.
> I have a question about the best way to debug apps which include
> dependencies.
> I'm working on an app, and so far, I've been testing it by using rebar to
> generate a release, then starting a console for the release and going from
> there.  The problem comes when I want to use something like dbg or appmon
> to debug errors or inspect the state of my app.  When I try to do, e.g.
> appmon:start() from the console for my release, it tells me "undefined
> function appmon:start/0".  I'm guessing this is because I didn't explicitly
> specify appmon in my release configuration?
> Alternatively, I created a start.sh shell script with contents like this:
> erl -pa apps/*/ebin -pa deps/*/ebin -eval 'application:start(dependency1),
> application:start(dependency2), application:start(myapp).'
> This lets me start appmon and whatever else I want when I run into errors,
> but feels pretty messy and wrong.
> I feel like I'm missing something really obvious here.  What's the correct
> way to do this?
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