External Build Systems

Jake can detect and run targets from Makefile and Justfile in the same directory as the active Jakefile. This lets you gradually migrate to Jake or use them together.

If you select a Jakefile with -f, external detection and delegation follow that Jakefile’s directory instead of your shell’s starting directory.

Automatic Detection

Jake automatically detects these files:

Makefile variants (in priority order):

• GNUmakefile
• Makefile
• makefile

Justfile variants (in priority order):

• justfile
• Justfile
• .justfile

Recipe Naming

External recipes get a prefix to avoid conflicts:

Source	Prefix	Example
Makefile	make.	make.build, make.clean
Justfile	just.	just.test, just.deploy

Listing External Recipes

# List all recipes including external
jake --list

# List only external recipes
jake --external

# List only Makefile targets
jake --external make

# List only Justfile recipes
jake --external just

# Hide external recipes from listing
jake --list --no-external

Running External Recipes

Run them like any other recipe:

# Run a Makefile target
jake make.build

# Run a Justfile recipe
jake just.test

# With arguments passed through to the delegated tool
jake make.install PREFIX=/usr/local
jake just.deploy production us-east-1

# External discovery also follows the selected Jakefile
jake -f tools/Jakefile make.build

How It Works

When you run an external recipe, Jake delegates to the underlying tool:

• Makefile: Runs make -f <file> <target>
• Justfile: Runs just --justfile <file> <recipe>

Any extra positional arguments after the external recipe are forwarded to the delegated tool.

The delegated process runs from the external file’s directory, so relative paths behave the same way they do when you invoke that Makefile or Justfile directly from its own directory.

Private Targets

Targets starting with _ are treated as private:

# Makefile
_helper:    # Hidden from jake --list
  echo "helper"

build: _helper
  echo "building"

Example: Mixed Project

Directory structure:

project/
├── Jakefile      # Jake recipes
├── Makefile      # Legacy build
└── justfile      # Additional tooling

# See everything
jake --list

# Output:
# Available recipes:
#   build         Build the project
#   test          Run tests
#
# Makefile (Makefile):
#   make.all
#   make.clean
#
# Justfile (justfile):
#   just.fmt      Format code
#   just.lint     Run linter

Gradual Migration

Use external support to migrate incrementally:

1. Create a Jakefile alongside your Makefile
2. Move recipes one at a time
3. Have Jake recipes call make targets during transition:

@description "New Jake build"
task build:
    # Can still call old make targets
    make legacy-step
    echo "New build steps..."

4. Remove Makefile when migration is complete