Justfile Patterns

Use this as a reference for common justfile patterns. Keep examples small and non-prescriptive. Prefer the repo’s existing recipes over copying templates.

Core Settings

set dotenv-load
set shell := ["bash", "-euco", "pipefail"]
set export

• dotenv-load explains implicit env loading from .env
• shell explains fail-fast behavior and shell-specific syntax
• export makes just variables available to recipe commands

Default Help Pattern

[private]
default:
    @just --list --unsorted

Use this when the repo wants just with no arguments to behave like help.

Parameterized Recipe

deploy env:
    ./scripts/deploy {{env}}

Use recipe arguments instead of hardcoding environment names or resources.

Variadic Recipe

test *args:
    uv run pytest {{args}}

Useful when the underlying tool already has a stable CLI and the recipe mostly adds project defaults.

Shebang Recipe

check:
    #!/usr/bin/env bash
    set -euo pipefail
    for cmd in jq rg just; do
        command -v "$cmd" >/dev/null || { echo "Missing: $cmd"; exit 1; }
    done

Use shebang recipes when multiple lines must share shell state.

Hidden Helper Recipe

[private]
_ensure-tools:
    #!/usr/bin/env bash
    command -v terraform >/dev/null

plan: _ensure-tools
    terraform plan

Remember that [private] helpers will not appear in just --list.

Confirmation Gate

[confirm("Destroy all resources?")]
destroy:
    terraform destroy

Use for destructive operations. Agents should treat these as intentional safety rails rather than friction to bypass.

Grouped Recipes

[group("ci")]
ci-test:
    cargo test

[group("deploy")]
deploy-prod:
    ./deploy production

Helpful when just --list doubles as the repo’s command menu.

Imports And Modules

import "ci.just"
mod deploy "deploy.just"

• import pulls in recipes from another file
• mod namespaces recipes, for example just deploy::prod

If a recipe seems missing, inspect the main justfile for import or mod before assuming the command surface is incomplete.

Project-Type Hints

Use these as discovery hints, not templates:

• Go repos often expose build, test, lint, fmt, and release helpers.
• Python repos often expose install, test, lint, fmt, and typecheck.
• Infra repos often expose init, plan, apply, destroy, and validation.
• Docker-heavy repos often expose image build/push recipes plus local run flows.

For all of them, prefer just --list and just --show over guessing.