External Build Systems

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

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)
jake make.install PREFIX=/usr/local

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>

The original tool handles all the execution logic.

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:

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

4. Remove Makefile when migration is complete