Directory Structure

Project Layout

Single-App Project:

my_app/
├── rebar.config           % Project configuration
├── rebar.lock             % Locked dependencies
├── src/                   % Source files
│   ├── my_app.app.src    % Application resource
│   └── *.erl             % Erlang modules
├── include/               % Header files
│   └── *.hrl
├── priv/                  % Private resources
├── test/                  % Test files (extra_src_dirs)
└── _build/                % Build output (gitignored)
    └── default/           % Default profile
        ├── lib/           % Dependencies + project
        │   ├── my_app/    % Project output
        │   │   ├── ebin/  % Compiled .beam files
        │   │   ├── priv/  % Copied priv resources
        │   │   └── ...
        │   └── dep_name/  % Each dependency
        ├── extras/        % Extra src_dirs output
        │   └── test/      % Test modules
        └── .rebar3/       % Rebar3 metadata
            └── */         % Compiler DAGs

Umbrella Project:

my_project/
├── rebar.config
├── apps/                  % Multiple applications
│   ├── app1/
│   │   ├── src/
│   │   │   ├── app1.app.src
│   │   │   └── *.erl
│   │   └── include/
│   └── app2/
│       └── src/
└── _build/
    └── default/
        └── lib/
            ├── app1/
            ├── app2/
            └── deps.../

Build Directories

Base Directory: _build/

• Default location for all build outputs
• Configurable via base_dir option or REBAR_BASE_DIR env var

Profile Directories: _build/PROFILE/

• Separate output for each profile (default, test, prod, etc.)
• Isolates artifacts between profiles

Lib Directory: _build/PROFILE/lib/

• Contains both dependencies and project applications
• Each app in its own subdirectory

Extras Directory: _build/PROFILE/extras/

• Output for extra_src_dirs (test, scripts, etc.)
• Not included in releases

Metadata Directory: _build/PROFILE/.rebar3/

• Compiler DAG files
• Other rebar3 metadata

Cache Directories

Global Cache: ~/.cache/rebar3/

• Default location (configurable via REBAR_CACHE_DIR)
• Hex packages
• Git repositories

Structure:

~/.cache/rebar3/
├── hex/
│   └── default/
│       └── packages/
│           ├── package-1.0.0.tar
│           └── package-1.0.0.etag
├── git/
│   └── repo-hash/         % Git clones
└── plugins/               % Global plugins

Configuration Directories

Global Config: ~/.config/rebar3/

~/.config/rebar3/
└── rebar.config           % Global configuration