--- disable-model-invocation: false name: cli-just user-invocable: false description: 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. --- # 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) set dotenv-load # Auto-load .env file set positional-arguments # Pass recipe args as $1, $2, etc. ``` ### Common Attributes | Attribute | Purpose | | ------------------------- | ---------------------------------------------- | | `[arg("p", long, ...)]` | Configure parameter as `--flag` option (v1.46) | | `[arg("p", pattern="…")]` | Constrain parameter to match regex pattern | | `[group("name")]` | Group recipes in `just --list` output | | `[no-cd]` | Don't change to justfile directory | | `[parallel]` | Run direct dependencies concurrently | | `[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 | ### Recipe Argument Flags (v1.46.0+) The `[arg()]` attribute configures parameters as CLI-style options: ```just # Long option (--target) [arg("target", long)] build target: cargo build --target {{ target }} # Short option (-v) [arg("verbose", short="v")] run verbose="false": echo "Verbose: {{ verbose }}" # Combined long + short [arg("output", long, short="o")] compile output: gcc main.c -o {{ output }} # Flag without value (presence sets to "true") [arg("release", long, value="true")] build release="false": cargo build {{ if release == "true" { "--release" } else { "" } }} # Help string (shown in `just --usage`) [arg("target", long, help="Build target architecture")] build target: cargo build --target {{ target }} ``` **Usage examples:** ```bash just build --target x86_64 just build --target=x86_64 just compile -o main just build --release just --usage build # Show recipe argument help ``` 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`, `MAGENTA` | 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 When designing recipes that use status reporting, check/write semantics, or alias conventions, see [references/patterns.md](references/patterns.md). ## Inline Scripts When writing recipes that need shell scripts (script attribute or shebang style), see [references/inline-scripts.md](references/inline-scripts.md). ## 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") # Usage: invoke directly in recipes (not with interpolation) build: bun next build ``` **Note:** `require()` validates the tool exists at recipe evaluation time. Use the variable name directly (e.g., `bun`), not with interpolation (`{{ bun }}`). ## 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: - **[`references/settings.md`](references/settings.md)** - Settings configuration and module system - **[`references/recipes.md`](references/recipes.md)** - Recipe attributes, parameters, dependencies, and prefixes - **[`references/syntax.md`](references/syntax.md)** - Constants, functions, variables, and CLI options - **[`references/patterns.md`](references/patterns.md)** - Established conventions, section organization, helper patterns ### Example Templates Working justfile templates in `examples/`: - **[`devkit.just`](examples/devkit.just)** - Minimal template importing @sablier/devkit - **[`standalone.just`](examples/standalone.just)** - Full standalone template with all patterns ### External Documentation - **Official Manual**: https://just.systems/man/en/ - **GitHub Repository**: https://github.com/casey/just - **Context7 Library ID**: `/websites/just_systems-man` ## No Justfile Formatter Do not use `just --fmt` or `just --dump`. The user has bespoke formatting preferences that the built-in formatter does not respect. Preserve existing formatting as-is. ## 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