Agent skill

tool-just-cli

This skill should be used when the user asks to "create a justfile", "write just recipes", "configure just settings", "add just modules", "use just attributes", "set up task automation", mentions justfile, just command runner, or task automation with just.

View SKILL.md on GitHub Repository
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Forks 31

Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/productivity/tool-just-cli

SKILL.md

Just Command Runner

Overview

Expert guidance for Just, a command runner with syntax inspired by make. Use this skill for creating justfiles, writing recipes, configuring settings, and implementing task automation workflows.

Key capabilities:

  • Create and organize justfiles with proper structure
  • Write recipes with attributes, dependencies, and parameters
  • Configure settings for shell, modules, and imports
  • Use built-in constants for terminal formatting
  • Implement check/write patterns for code quality tools

Quick Reference

Essential Settings

just
set allow-duplicate-recipes       # Allow recipes to override imported ones
set allow-duplicate-variables     # Allow variables to override imported ones
set shell := ["bash", "-euo", "pipefail", "-c"]  # Strict bash with error handling
set unstable                      # Enable unstable features (modules, script attribute)

Environment Variables: Use mise for environment variable management instead of Just's dotenv settings. mise provides project-scoped env vars via .mise.toml with better tooling integration.

Common Attributes

Attribute Purpose
[group("name")] Group recipes in just --list output
[no-cd] Don't change to justfile directory
[private] Hide from just --list (same as _ prefix)
[script] Execute recipe as single script block
[script("interpreter")] Use specific interpreter (bash, python, etc.)
[confirm("prompt")] Require user confirmation before running
[doc("text")] Override recipe documentation
[positional-arguments] Enable positional args for this recipe only

Multiple attributes can be combined:

just
[no-cd, private]
[group("checks")]
recipe:
    echo "hello"

Built-in Constants

Terminal formatting constants are globally available (no definition needed):

Constant Description
CYAN, GREEN, RED, YELLOW, BLUE, PURPLE Text colors
BOLD, ITALIC, UNDERLINE, STRIKETHROUGH Text styles
NORMAL Reset formatting
BG_* Background colors (BG_RED, BG_GREEN, etc.)
HEX, HEXLOWER Hexadecimal digits

Usage:

just
@status:
    echo -e '{{ GREEN }}Success!{{ NORMAL }}'
    echo -e '{{ BOLD + CYAN }}Building...{{ NORMAL }}'

Key Functions

just
# Require executable exists (fails recipe if not found)
jq := require("jq")

# Get environment variable with default
log_level := env("LOG_LEVEL", "info")

# Get justfile directory path
root := justfile_dir()

Recipe Patterns

Status Reporter Pattern

Display formatted status during multi-step workflows:

just
@_run-with-status recipe *args:
    echo ""
    echo -e '{{ CYAN }}→ Running {{ recipe }}...{{ NORMAL }}'
    just {{ recipe }} {{ args }}
    echo -e '{{ GREEN }}✓ {{ recipe }} completed{{ NORMAL }}'
alias rws := _run-with-status

Check/Write Pattern

Pair check (verify) and write (fix) recipes for code quality tools:

just
[group("checks")]
@biome-check +globs=".":
    na biome check {{ globs }}
alias bc := biome-check

[group("checks")]
@biome-write +globs=".":
    na biome check --write {{ globs }}
alias bw := biome-write

Full Check/Write Pattern

Aggregate all checks with status reporting:

just
[group("checks")]
@full-check:
    just _run-with-status biome-check
    just _run-with-status prettier-check
    just _run-with-status tsc-check
    echo ""
    echo -e '{{ GREEN }}All code checks passed!{{ NORMAL }}'
alias fc := full-check

[group("checks")]
@full-write:
    just _run-with-status biome-write
    just _run-with-status prettier-write
    echo ""
    echo -e '{{ GREEN }}All code fixes applied!{{ NORMAL }}'
alias fw := full-write

Standard Alias Conventions

Recipe Alias Recipe Alias
full-check fc full-write fw
biome-check bc biome-write bw
prettier-check pc prettier-write pw
mdformat-check mc mdformat-write mw
tsc-check tc ruff-check rc
test t build b

Modules & Imports

Import Pattern

Include recipes from another file:

just
import "./just/settings.just"
import "./just/base.just"
import? "./local.just"    # Optional (no error if missing)

Module Pattern

Load submodule (requires set unstable):

just
mod foo                   # Loads foo.just or foo/justfile
mod bar "path/to/bar"     # Custom path
mod? optional             # Optional module

# Call module recipes
just foo::build

Devkit Import Pattern

For projects using @sablier/devkit:

just
import "./node_modules/@sablier/devkit/just/base.just"
import "./node_modules/@sablier/devkit/just/npm.just"

Section Organization

Standard section header format:

just
# ---------------------------------------------------------------------------- #
#                                 DEPENDENCIES                                 #
# ---------------------------------------------------------------------------- #

Common sections (in order):

  1. DEPENDENCIES - Required tools with URLs
  2. CONSTANTS - Glob patterns, environment vars
  3. RECIPES / COMMANDS - Main entry points
  4. CHECKS - Code quality recipes
  5. UTILITIES / INTERNAL HELPERS - Private helpers

Default Recipe

Always define a default recipe:

just
# Show available commands
default:
    @just --list

Dependencies Declaration

Document required tools at the top:

just
# ---------------------------------------------------------------------------- #
#                                 DEPENDENCIES                                 #
# ---------------------------------------------------------------------------- #

# Bun: https://bun.sh
bun := require("bun")

# Ni: https://github.com/antfu-collective/ni
na := require("na")
ni := require("ni")
nlx := require("nlx")

Context7 Fallback

For Just features not covered in this skill (new attributes, advanced functions, edge cases), fetch the latest documentation:

Use context7 MCP with library ID `/websites/just_systems-man` to get up-to-date Just documentation.

Example topics to search:

  • modules import mod - Module system details
  • settings - All available settings
  • attributes - Recipe attributes
  • functions - Built-in functions
  • script recipes - Script block syntax

Additional Resources

Reference Files

For detailed patterns and comprehensive coverage, consult:

  • reference.md - Complete settings, modules, attributes, functions reference
  • patterns.md - Established conventions, section organization, helper patterns

External Documentation

Important Limitations

Just does not support flags. Recipe parameters are positional only:

just
# WRONG: Flags don't work
build --release:  # This won't work!

# CORRECT: Use positional parameters
build mode="debug":
    cargo build {{ if mode == "release" { "--release" } else { "" } }}

# Usage: just build release

For complex flag-like behavior, use environment variables or positional parameters with defaults.

Tips

  1. Use @ prefix to suppress command echo: @echo "quiet"
  2. Use + for variadic parameters: test +args
  3. Use * for optional variadic: build *flags
  4. Quote glob patterns in variables: GLOBS := "\"**/*.json\""
  5. Use [no-cd] in monorepos to stay in current directory
  6. Private recipes start with _ or use [private]
  7. Always define aliases after recipe names for discoverability

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