Rebar3 builds

New project

Rebar3 is the standard build tool. The new command scaffolds a project from a template: app for a library, escript for a command line tool.

Answer the prompts and the skeleton appears in a folder with your project name.

rebar3 new app myapp

==> Writing myapp/src/myapp_app.erl

==> Writing myapp/src/myapp_sup.erl

==> Writing myapp/rebar.config

Project layout

Source lives in src, tests in test, and build products in _build. The rebar.config file holds the project settings and dependencies.

The scaffold also writes an OTP application skeleton with a supervisor, which lessons 35 and 36 explain.

myapp/

rebar.config

src/myapp_app.erl

src/myapp_sup.erl

test/

_build/

Compile

The compile task builds every module in src and leaves beam files under _build. Rebar3 tracks dependencies and only rebuilds what changed.

Warnings from the compiler appear in the output; treat them as errors until the project is green.

rebar3 compile

==> Compiling myapp

==> App myapp compiled to _build/default/lib/myapp/ebin

Run it

The shell task starts an erl with the project on the code path. Your modules are already loaded and ready to call.

For a one-off run without the shell, use the escript template or erl with the -pa flag pointing at the ebin folder.

rebar3 shell

==> Booted myapp

Eshell V15.2 (abort with ^G)

Next: Testing with EUnit

Article author: Arthur Isaev