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just





  

    crates.io version

  

  

    build status

  

  

    downloads

  

  

    chat on discord

  

  

    say thanks

  







`just` is a handy way to save and run project-specific commands.



This readme is also available as a [book](https://just.systems/man/en/).



(中文文档在 [这里](https://github.com/casey/just/blob/master/README.中文.md),

快看过来!)



Commands, called recipes, are stored in a file called `justfile` with syntax

inspired by `make`:



![screenshot](https://raw.githubusercontent.com/casey/just/master/screenshot.png)



You can then run them with `just RECIPE`:



```console

$ just test-all

cc *.c -o main

./test --all

Yay, all your tests passed!

```



`just` has a ton of useful features, and many improvements over `make`:



- `just` is a command runner, not a build system, so it avoids much of

  [`make`'s complexity and idiosyncrasies](#what-are-the-idiosyncrasies-of-make-that-just-avoids).

  No need for `.PHONY` recipes!



- Linux, MacOS, and Windows are supported with no additional dependencies.

  (Although if your system doesn't have an `sh`, you'll need to

  [choose a different shell](#shell).)



- Errors are specific and informative, and syntax errors are reported along

  with their source context.



- Recipes can accept [command line arguments](#recipe-parameters).



- Wherever possible, errors are resolved statically. Unknown recipes and

  circular dependencies are reported before anything runs.



- `just` [loads `.env` files](#dotenv-settings), making it easy to populate

  environment variables.



- Recipes can be [listed from the command line](#listing-available-recipes).



- Command line completion scripts are

  [available for most popular shells](#shell-completion-scripts).



- Recipes can be written in

  [arbitrary languages](#shebang-recipes), like Python or NodeJS.



- `just` can be invoked from any subdirectory, not just the directory that

  contains the `justfile`.



- And [much more](https://just.systems/man/en/)!



If you need help with `just` please feel free to open an issue or ping me on

[Discord](https://discord.gg/ezYScXR). Feature requests and bug reports are

always welcome!



Installation

------------



### Prerequisites



`just` should run on any system with a reasonable `sh`, including Linux, MacOS,

and the BSDs.



On Windows, `just` works with the `sh` provided by

[Git for Windows](https://git-scm.com),

[GitHub Desktop](https://desktop.github.com), or

[Cygwin](http://www.cygwin.com).



If you'd rather not install `sh`, you can use the `shell` setting to use the

shell of your choice.



Like PowerShell:



```just

# use PowerShell instead of sh:

set shell := ["powershell.exe", "-c"]



hello:

  Write-Host "Hello, world!"

```



…or `cmd.exe`:



```just

# use cmd.exe instead of sh:

set shell := ["cmd.exe", "/c"]



list:

  dir

```



You can also set the shell using command-line arguments. For example, to use

PowerShell, launch `just` with `--shell powershell.exe --shell-arg -c`.



(PowerShell is installed by default on Windows 7 SP1 and Windows Server 2008 R2

S1 and later, and `cmd.exe` is quite fiddly, so PowerShell is recommended for

most Windows users.)



### Packages



#### Cross-platform



  

    

      Package Manager

      Package

      Command

    

  

  

    

      asdf

      just

      

        asdf plugin add just


        asdf install just <version>

      

    

    

      Cargo

      just

      cargo install just

    

    

      Conda

      just

      conda install -c conda-forge just

    

    

      Homebrew

      just

      brew install just

    

    

      Nix

      just

      nix-env -iA nixpkgs.just

    

    

      npm

      rust-just

      npm install rust-just

    

    

      PyPI

      rust-just

      pipx install rust-just

    

  



#### BSD



  

    

      Operating System

      Package Manager

      Package

      Command

    

  

  

    

      FreeBSD

      pkg

      just

      pkg install just

    

  



#### Linux



  

    

      Operating System

      Package Manager

      Package

      Command

    

  

  

    

      Alpine

      apk-tools

      just

      apk add just

    

    

      Arch

      pacman

      just

      pacman -S just

    

    

      

        Debian 13 (unreleased) and

        Ubuntu 24.04 derivatives

      apt

      just

      apt install just

    

    

      Debian and Ubuntu derivatives

      MPR

      just

      

        git clone https://mpr.makedeb.org/just


        cd just


        makedeb -si

      

    

    

      Debian and Ubuntu derivatives

      Prebuilt-MPR

      just

      

        You must have the Prebuilt-MPR set up on your system in order to run this command.


        apt install just

      

    

    

      Fedora

      DNF

      just

      dnf install just

    

    

      Gentoo

      Portage

      guru/dev-build/just

      

        eselect repository enable guru


        emerge --sync guru


        emerge dev-build/just

      

    

    

      NixOS

      Nix

      just

      nix-env -iA nixos.just

    

    

      openSUSE

      Zypper

      just

      zypper in just

    

    

      Solus

      eopkg

      just

      eopkg install just

    

    

      Void

      XBPS

      just

      xbps-install -S just

    

  



#### Windows



  

    

      Package Manager

      Package

      Command

    

  

  

    

      Chocolatey

      just

      choco install just

    

    

      Scoop

      just

      scoop install just

    

    

      Windows Package Manager

      Casey/Just

      winget install --id Casey.Just --exact

    

  



#### macOS



  

    

      Package Manager

      Package

      Command

    

  

  

    

      MacPorts

      just

      port install just

    

  



![just package version table](https://repology.org/badge/vertical-allrepos/just.svg)



![rust:just package version table](https://repology.org/badge/vertical-allrepos/rust:just.svg)



### Pre-Built Binaries



Pre-built binaries for Linux, MacOS, and Windows can be found on

[the releases page](https://github.com/casey/just/releases).



You can use the following command on Linux, MacOS, or Windows to download the

latest release, just replace `DEST` with the directory where you'd like to put

`just`:



```console

curl --proto '=https' --tlsv1.2 -sSf https://just.systems/install.sh | bash -s -- --to DEST

```



For example, to install `just` to `~/bin`:



```console

# create ~/bin

mkdir -p ~/bin



# download and extract just to ~/bin/just

curl --proto '=https' --tlsv1.2 -sSf https://just.systems/install.sh | bash -s -- --to ~/bin



# add `~/bin` to the paths that your shell searches for executables

# this line should be added to your shells initialization file,

# e.g. `~/.bashrc` or `~/.zshrc`

export PATH="$PATH:$HOME/bin"



# just should now be executable

just --help

```



Note that `install.sh` may fail on GitHub Actions, or in other environments

where many machines share IP addresses. `install.sh` calls GitHub APIs in order

to determine the latest version of `just` to install, and those API calls are

rate-limited on a per-IP basis. To make `install.sh` more reliable in such

circumstances, pass a specific tag to install with `--tag`.



[Releases](https://github.com/casey/just/releases) include a `SHA256SUM` file

which can be used to verify the integrity of pre-built binary archives.



To verify a release, download the pre-built binary archive along with the

`SHA256SUM` file and run:



```sh

shasum --algorithm 256 --ignore-missing --check SHA256SUMS

```



### GitHub Actions



`just` can be installed on GitHub Actions in a few ways.



Using package managers pre-installed on GitHub Actions runners on MacOS with

`brew install just`, and on Windows with `choco install just`.



With [extractions/setup-just](https://github.com/extractions/setup-just):



```yaml

- uses: extractions/setup-just@v1

  with:

    just-version: 1.5.0  # optional semver specification, otherwise latest

```



Or with [taiki-e/install-action](https://github.com/taiki-e/install-action):



```yaml

- uses: taiki-e/install-action@just

```



### Release RSS Feed



An [RSS feed](https://en.wikipedia.org/wiki/RSS) of `just` releases is available [here](https://github.com/casey/just/releases.atom).



### Node.js Installation



[just-install](https://npmjs.com/package/just-install) can be used to automate

installation of `just` in Node.js applications.



`just` is a great, more robust alternative to npm scripts. If you want to

include `just` in the dependencies of a Node.js application, `just-install`

will install a local, platform-specific binary as part of the `npm install`

command. This removes the need for every developer to install `just`

independently using one of the processes mentioned above. After installation,

the `just` command will work in npm scripts or with npx. It's great for teams

who want to make the set up process for their project as easy as possible.



For more information, see the

[just-install README file](https://github.com/brombal/just-install#readme).



Backwards Compatibility

-----------------------



With the release of version 1.0, `just` features a strong commitment to

backwards compatibility and stability.



Future releases will not introduce backwards incompatible changes that make

existing `justfile`s stop working, or break working invocations of the

command-line interface.



This does not, however, preclude fixing outright bugs, even if doing so might

break `justfiles` that rely on their behavior.



There will never be a `just` 2.0. Any desirable backwards-incompatible changes

will be opt-in on a per-`justfile` basis, so users may migrate at their

leisure.



Features that aren't yet ready for stabilization are marked as unstable and may

be changed or removed at any time. Using unstable features produces an error by

default, which can be suppressed with by passing the `--unstable` flag,

`set unstable`, or setting the environment variable `JUST_UNSTABLE`, to any

value other than `false`, `0`, or the empty string.



Editor Support

--------------



`justfile` syntax is close enough to `make` that you may want to tell your

editor to use `make` syntax highlighting for `just`.



### Vim and Neovim



#### `vim-just`



The [vim-just](https://github.com/NoahTheDuke/vim-just) plugin provides syntax

highlighting for `justfile`s.



Install it with your favorite package manager, like

[Plug](https://github.com/junegunn/vim-plug):



```vim

call plug#begin()



Plug 'NoahTheDuke/vim-just'



call plug#end()

```



Or with Vim's built-in package support:



```console

mkdir -p ~/.vim/pack/vendor/start

cd ~/.vim/pack/vendor/start

git clone https://github.com/NoahTheDuke/vim-just.git

```



#### `tree-sitter-just`



[tree-sitter-just](https://github.com/IndianBoy42/tree-sitter-just) is an

[Nvim Treesitter](https://github.com/nvim-treesitter/nvim-treesitter) plugin

for Neovim.



#### Makefile Syntax Highlighting



Vim's built-in makefile syntax highlighting isn't perfect for `justfile`s, but

it's better than nothing. You can put the following in `~/.vim/filetype.vim`:



```vimscript

if exists("did_load_filetypes")

  finish

endif



augroup filetypedetect

  au BufNewFile,BufRead justfile setf make

augroup END

```



Or add the following to an individual `justfile` to enable `make` mode on a

per-file basis:



```text

# vim: set ft=make :

```



### Emacs



[just-mode](https://github.com/leon-barrett/just-mode.el) provides syntax

highlighting and automatic indentation of `justfile`s. It is available on

[MELPA](https://melpa.org/) as [just-mode](https://melpa.org/#/just-mode).



[justl](https://github.com/psibi/justl.el) provides commands for executing and

listing recipes.



You can add the following to an individual `justfile` to enable `make` mode on

a per-file basis:



```text

# Local Variables:

# mode: makefile

# End:

```



### Visual Studio Code



An extension for VS Code is [available here](https://github.com/nefrob/vscode-just).



Unmaintained VS Code extensions include

[skellock/vscode-just](https://github.com/skellock/vscode-just) and

[sclu1034/vscode-just](https://github.com/sclu1034/vscode-just).



### JetBrains IDEs



A plugin for JetBrains IDEs by [linux_china](https://github.com/linux-china) is

[available here](https://plugins.jetbrains.com/plugin/18658-just).



### Kakoune



Kakoune supports `justfile` syntax highlighting out of the box, thanks to

TeddyDD.



### Helix



[Helix](https://helix-editor.com/) supports `justfile` syntax highlighting

out-of-the-box since version 23.05.



### Sublime Text



The [Just package](https://github.com/nk9/just_sublime) by

[nk9](https://github.com/nk9) with `just` syntax and some other tools is

available on [PackageControl](https://packagecontrol.io/packages/Just).



### Micro



[Micro](https://micro-editor.github.io/) supports Justfile syntax highlighting

out of the box, thanks to [tomodachi94](https://github.com/tomodachi94).



### Other Editors



Feel free to send me the commands necessary to get syntax highlighting working

in your editor of choice so that I may include them here.



Quick Start

-----------



See [the installation section](#installation) for how to install `just` on your

computer. Try running `just --version` to make sure that it's installed

correctly.



For an overview of the syntax, check out

[this cheatsheet](https://cheatography.com/linux-china/cheat-sheets/justfile/).



Once `just` is installed and working, create a file named `justfile` in the

root of your project with the following contents:



```just

recipe-name:

  echo 'This is a recipe!'



# this is a comment

another-recipe:

  @echo 'This is another recipe.'

```



When you invoke `just` it looks for file `justfile` in the current directory

and upwards, so you can invoke it from any subdirectory of your project.



The search for a `justfile` is case insensitive, so any case, like `Justfile`,

`JUSTFILE`, or `JuStFiLe`, will work. `just` will also look for files with the

name `.justfile`, in case you'd like to hide a `justfile`.



Running `just` with no arguments runs the first recipe in the `justfile`:



```console

$ just

echo 'This is a recipe!'

This is a recipe!

```



One or more arguments specify the recipe(s) to run:



```console

$ just another-recipe

This is another recipe.

```



`just` prints each command to standard error before running it, which is why

`echo 'This is a recipe!'` was printed. This is suppressed for lines starting

with `@`, which is why `echo 'This is another recipe.'` was not printed.



Recipes stop running if a command fails. Here `cargo publish` will only run if

`cargo test` succeeds:



```just

publish:

  cargo test

  # tests passed, time to publish!

  cargo publish

```



Recipes can depend on other recipes. Here the `test` recipe depends on the

`build` recipe, so `build` will run before `test`:



```just

build:

  cc main.c foo.c bar.c -o main



test: build

  ./test



sloc:

  @echo "`wc -l *.c` lines of code"

```



```console

$ just test

cc main.c foo.c bar.c -o main

./test

testing… all tests passed!

```



Recipes without dependencies will run in the order they're given on the command

line:



```console

$ just build sloc

cc main.c foo.c bar.c -o main

1337 lines of code

```



Dependencies will always run first, even if they are passed after a recipe that

depends on them:



```console

$ just test build

cc main.c foo.c bar.c -o main

./test

testing… all tests passed!

```



Examples

--------



A variety of `justfile`s can be found in the

[examples directory](https://github.com/casey/just/tree/master/examples) and on

[GitHub](https://github.com/search?q=path%3A**%2Fjustfile&type=code).



Features

--------



### The Default Recipe



When `just` is invoked without a recipe, it runs the first recipe in the

`justfile`. This recipe might be the most frequently run command in the

project, like running the tests:



```just

test:

  cargo test

```



You can also use dependencies to run multiple recipes by default:



```just

default: lint build test



build:

  echo Building…



test:

  echo Testing…



lint:

  echo Linting…

```



If no recipe makes sense as the default recipe, you can add a recipe to the

beginning of your `justfile` that lists the available recipes:



```just

default:

  just --list

```



### Listing Available Recipes



Recipes can be listed in alphabetical order with `just --list`:



```console

$ just --list

Available recipes:

    build

    test

    deploy

    lint

```



Recipes in [submodules](#modules1190) can be listed with `just --list PATH`,

where `PATH` is a space- or `::`-separated module path:



```

$ cat justfile

mod foo

$ cat foo.just

mod bar

$ cat bar.just

baz:

$ just foo bar

Available recipes:

    baz

$ just foo::bar

Available recipes:

    baz

```



`just --summary` is more concise:



```console

$ just --summary

build test deploy lint

```



Pass `--unsorted` to print recipes in the order they appear in the `justfile`:



```just

test:

  echo 'Testing!'



build:

  echo 'Building!'

```



```console

$ just --list --unsorted

Available recipes:

    test

    build

```



```console

$ just --summary --unsorted

test build

```



If you'd like `just` to default to listing the recipes in the `justfile`, you

can use this as your default recipe:



```just

default:

  @just --list

```



Note that you may need to add `--justfile {{justfile()}}` to the line above.

Without it, if you executed `just -f /some/distant/justfile -d .` or

`just -f ./non-standard-justfile`, the plain `just --list` inside the recipe

would not necessarily use the file you provided. It would try to find a

justfile in your current path, maybe even resulting in a `No justfile found`

error.



The heading text can be customized with `--list-heading`:



```console

$ just --list --list-heading $'Cool stuff…\n'

Cool stuff…

    test

    build

```



And the indentation can be customized with `--list-prefix`:



```console

$ just --list --list-prefix ····

Available recipes:

····test

····build

```



The argument to `--list-heading` replaces both the heading and the newline

following it, so it should contain a newline if non-empty. It works this way so

you can suppress the heading line entirely by passing the empty string:



```console

$ just --list --list-heading ''

    test

    build

```



### Invoking Multiple Recipes



Multiple recipes may be invoked on the command line at once:



```just

build:

  make web



serve:

  python3 -m http.server -d out 8000

```



```console

$ just build serve

make web

python3 -m http.server -d out 8000

```



Keep in mind that recipes with parameters will swallow arguments, even if they

match the names of other recipes:



```just

build project:

  make {{project}}



serve:

  python3 -m http.server -d out 8000

```



```console

$ just build serve

make: *** No rule to make target `serve'.  Stop.

```



The `--one` flag can be used to restrict command-line invocations to a single

recipe:



```console

$ just --one build serve

error: Expected 1 command-line recipe invocation but found 2.

```



### Working Directory



By default, recipes run with the working directory set to the directory that

contains the `justfile`.



The `[no-cd]` attribute can be used to make recipes run with the working

directory set to directory in which `just` was invoked.



```just

@foo:

  pwd



[no-cd]

@bar:

  pwd

```



```console

$ cd subdir

$ just foo

/

$ just bar

/subdir

```



You can override working directory with `set working-directory := '…'`, whose value

is relative to the default working directory.



```just

set working-directory := 'bar'



@foo:

  pwd

```



```console

$ pwd

/home/bob

$ just foo

/home/bob/bar

```



### Aliases



Aliases allow recipes to be invoked on the command line with alternative names:



```just

alias b := build



build:

  echo 'Building!'

```



```console

$ just b

echo 'Building!'

Building!

```



### Settings



Settings control interpretation and execution. Each setting may be specified at

most once, anywhere in the `justfile`.



For example:



```just

set shell := ["zsh", "-cu"]



foo:

  # this line will be run as `zsh -cu 'ls **/*.txt'`

  ls **/*.txt

```



#### Table of Settings



| Name | Value | Default | Description |

|------|-------|---------|-------------|

| `allow-duplicate-recipes` | boolean | `false` | Allow recipes appearing later in a `justfile` to override earlier recipes with the same name. |

| `allow-duplicate-variables` | boolean | `false` | Allow variables appearing later in a `justfile` to override earlier variables with the same name. |

| `dotenv-filename` | string | - | Load a `.env` file with a custom name, if present. |

| `dotenv-load` | boolean | `false` | Load a `.env` file, if present. |

| `dotenv-path` | string | - | Load a `.env` file from a custom path and error if not present. Overrides `dotenv-filename`. |

| `dotenv-required` | boolean | `false` | Error if a `.env` file isn't found. |

| `export` | boolean | `false` | Export all variables as environment variables. |

| `fallback` | boolean | `false` | Search `justfile` in parent directory if the first recipe on the command line is not found. |

| `ignore-comments` | boolean | `false` | Ignore recipe lines beginning with `#`. |

| `positional-arguments` | boolean | `false` | Pass positional arguments. |

| `script-interpreter`1.33.0 | `[COMMAND, ARGS…]` | `['sh', '-eu']` | Set command used to invoke recipes with empty `[script]` attribute. |

| `shell` | `[COMMAND, ARGS…]` | - | Set command used to invoke recipes and evaluate backticks. |

| `tempdir` | string | - | Create temporary directories in `tempdir` instead of the system default temporary directory. |

| `unstable`1.31.0 | boolean | `false` | Enable unstable features. |

| `windows-powershell` | boolean | `false` | Use PowerShell on Windows as default shell. (Deprecated. Use `windows-shell` instead. |

| `windows-shell` | `[COMMAND, ARGS…]` | - | Set the command used to invoke recipes and evaluate backticks. |

| `working-directory`1.33.0 | string | - | Set the working directory for recipes and backticks, relative to the default working directory. |



Boolean settings can be written as:



```justfile

set NAME

```



Which is equivalent to:



```justfile

set NAME := true

```



#### Allow Duplicate Recipes



If `allow-duplicate-recipes` is set to `true`, defining multiple recipes with

the same name is not an error and the last definition is used. Defaults to

`false`.



```just

set allow-duplicate-recipes



@foo:

  echo foo



@foo:

  echo bar

```



```console

$ just foo

bar

```



#### Allow Duplicate Variables



If `allow-duplicate-variables` is set to `true`, defining multiple variables

with the same name is not an error and the last definition is used. Defaults to

`false`.



```just

set allow-duplicate-variables



a := "foo"

a := "bar"



@foo:

  echo $a

```



```console

$ just foo

bar

```



#### Dotenv Settings



If any of `dotenv-load`, `dotenv-filename`, `dotenv-path`, or `dotenv-required`

are set, `just` will try to load environment variables from a file.



If `dotenv-path` is set, `just` will look for a file at the given path, which

may be absolute, or relative to the working directory.



The command-line option `--dotenv-path`, short form `-E`, can be used to set or

override `dotenv-path` at runtime.



If `dotenv-filename` is set `just` will look for a file at the given path,

relative to the working directory and each of its ancestors.



If `dotenv-filename` is not set, but `dotenv-load` or `dotenv-required` are

set, just will look for a file named `.env`, relative to the working directory

and each of its ancestors.



`dotenv-filename` and `dotenv-path` are similar, but `dotenv-path` is only

checked relative to the working directory, whereas `dotenv-filename` is checked

relative to the working directory and each of its ancestors.



It is not an error if an environment file is not found, unless

`dotenv-required` is set.



The loaded variables are environment variables, not `just` variables, and so

must be accessed using `$VARIABLE_NAME` in recipes and backticks.



For example, if your `.env` file contains:



```console

# a comment, will be ignored

DATABASE_ADDRESS=localhost:6379

SERVER_PORT=1337

```



And your `justfile` contains:



```just

set dotenv-load



serve:

  @echo "Starting server with database $DATABASE_ADDRESS on port $SERVER_PORT…"

  ./server --database $DATABASE_ADDRESS --port $SERVER_PORT

```



`just serve` will output:



```console

$ just serve

Starting server with database localhost:6379 on port 1337…

./server --database $DATABASE_ADDRESS --port $SERVER_PORT

```



#### Export



The `export` setting causes all `just` variables to be exported as environment

variables. Defaults to `false`.



```just

set export



a := "hello"



@foo b:

  echo $a

  echo $b

```



```console

$ just foo goodbye

hello

goodbye

```



#### Positional Arguments



If `positional-arguments` is `true`, recipe arguments will be passed as

positional arguments to commands. For linewise recipes, argument `$0` will be

the name of the recipe.



For example, running this recipe:



```just

set positional-arguments



@foo bar:

  echo $0

  echo $1

```



Will produce the following output:



```console

$ just foo hello

foo

hello

```



When using an `sh`-compatible shell, such as `bash` or `zsh`, `$@` expands to

the positional arguments given to the recipe, starting from one. When used

within double quotes as `"$@"`, arguments including whitespace will be passed

on as if they were double-quoted. That is, `"$@"` is equivalent to `"$1" "$2"`…

When there are no positional parameters, `"$@"` and `$@` expand to nothing

(i.e., they are removed).



This example recipe will print arguments one by one on separate lines:



```just

set positional-arguments



@test *args='':

  bash -c 'while (( "$#" )); do echo - $1; shift; done' -- "$@"

```



Running it with _two_ arguments:



```console

$ just test foo "bar baz"

- foo

- bar baz

```



Positional arguments may also be turned on on a per-recipe basis with the

`[positional-arguments]` attribute1.29.0:



```just

[positional-arguments]

@foo bar:

  echo $0

  echo $1

```



Note that PowerShell does not handle positional arguments in the same way as

other shells, so turning on positional arguments will likely break recipes that

use PowerShell.



If using PowerShell 7.4 or better, the `-CommandWithArgs` flag will make

positional arguments work as expected:



```just

set shell := ['pwsh.exe', '-CommandWithArgs']

set positional-arguments



print-args a b c:

  Write-Output @($args[1..($args.Count - 1)])

```



#### Shell



The `shell` setting controls the command used to invoke recipe lines and

backticks. Shebang recipes are unaffected. The default shell is `sh -cu`.



```just

# use python3 to execute recipe lines and backticks

set shell := ["python3", "-c"]



# use print to capture result of evaluation

foos := `print("foo" * 4)`



foo:

  print("Snake snake snake snake.")

  print("{{foos}}")

```



`just` passes the command to be executed as an argument. Many shells will need

an additional flag, often `-c`, to make them evaluate the first argument.



##### Windows Shell



`just` uses `sh` on Windows by default. To use a different shell on Windows,

use `windows-shell`:



```just

set windows-shell := ["powershell.exe", "-NoLogo", "-Command"]



hello:

  Write-Host "Hello, world!"

```



See

[powershell.just](https://github.com/casey/just/blob/master/examples/powershell.just)

for a justfile that uses PowerShell on all platforms.



##### Windows PowerShell



*`set windows-powershell` uses the legacy `powershell.exe` binary, and is no

longer recommended. See the `windows-shell` setting above for a more flexible

way to control which shell is used on Windows.*



`just` uses `sh` on Windows by default. To use `powershell.exe` instead, set

`windows-powershell` to true.



```just

set windows-powershell := true



hello:

  Write-Host "Hello, world!"

```



##### Python 3



```just

set shell := ["python3", "-c"]

```



##### Bash



```just

set shell := ["bash", "-uc"]

```



##### Z Shell



```just

set shell := ["zsh", "-uc"]

```



##### Fish



```just

set shell := ["fish", "-c"]

```



##### Nushell



```just

set shell := ["nu", "-c"]

```



If you want to change the default table mode to `light`:



```just

set shell := ['nu', '-m', 'light', '-c']

```



*[Nushell](https://github.com/nushell/nushell) was written in Rust, and **has

cross-platform support for Windows / macOS and Linux**.*



### Documentation Comments



Comments immediately preceding a recipe will appear in `just --list`:



```just

# build stuff

build:

  ./bin/build



# test stuff

test:

  ./bin/test

```



```console

$ just --list

Available recipes:

    build # build stuff

    test # test stuff

```



The `[doc]` attribute can be used to set or suppress a recipe's doc comment:



```just

# This comment won't appear

[doc('Build stuff')]

build:

  ./bin/build



# This one won't either

[doc]

test:

  ./bin/test

```



```console

$ just --list

Available recipes:

    build # Build stuff

    test

```



### Variables and Substitution



Variables, strings, concatenation, path joining, and substitution using `{{…}}`

are supported:



```just

tmpdir  := `mktemp -d`

version := "0.2.7"

tardir  := tmpdir / "awesomesauce-" + version

tarball := tardir + ".tar.gz"



publish:

  rm -f {{tarball}}

  mkdir {{tardir}}

  cp README.md *.c {{tardir}}

  tar zcvf {{tarball}} {{tardir}}

  scp {{tarball}} [email protected]:release/

  rm -rf {{tarball}} {{tardir}}

```



#### Joining Paths



The `/` operator can be used to join two strings with a slash:



```just

foo := "a" / "b"

```



```

$ just --evaluate foo

a/b

```



Note that a `/` is added even if one is already present:



```just

foo := "a/"

bar := foo / "b"

```



```

$ just --evaluate bar

a//b

```



Absolute paths can also be constructed1.5.0:



```just

foo := / "b"

```



```

$ just --evaluate foo

/b

```



The `/` operator uses the `/` character, even on Windows. Thus, using the `/`

operator should be avoided with paths that use universal naming convention

(UNC), i.e., those that start with `\?`, since forward slashes are not

supported with UNC paths.



#### Escaping `{{`



To write a recipe containing `{{`, use `{{{{`:



```just

braces:

  echo 'I {{{{LOVE}} curly braces!'

```



(An unmatched `}}` is ignored, so it doesn't need to be escaped.)



Another option is to put all the text you'd like to escape inside of an

interpolation:



```just

braces:

  echo '{{'I {{LOVE}} curly braces!'}}'

```



Yet another option is to use `{{ "{{" }}`:



```just

braces:

  echo 'I {{ "{{" }}LOVE}} curly braces!'

```



### Strings



Double-quoted strings support escape sequences:



```just

carriage-return   := "\r"

double-quote      := "\""

newline           := "\n"

no-newline        := "\

"

slash             := "\\"

tab               := "\t"

unicode-codepoint := "\u{1F916}"

```



```console

$ just --evaluate

"arriage-return   := "

double-quote      := """

newline           := "

"

no-newline        := ""

slash             := "\"

tab               := "     "

unicode-codepoint := "🤖"

```



The unicode character escape sequence `\u{…}`1.36.0 accepts up to

six hex digits.



Strings may contain line breaks:



```just

single := '

hello

'



double := "

goodbye

"

```



Single-quoted strings do not recognize escape sequences:



```just

escapes := '\t\n\r\"\\'

```



```console

$ just --evaluate

escapes := "\t\n\r\"\\"

```



Indented versions of both single- and double-quoted strings, delimited by

triple single- or double-quotes, are supported. Indented string lines are

stripped of a leading line break, and leading whitespace common to all

non-blank lines:



```just

# this string will evaluate to `foo\nbar\n`

x := '''

  foo

  bar

'''



# this string will evaluate to `abc\n  wuv\nxyz\n`

y := """

  abc

    wuv

  xyz

"""

```



Similar to unindented strings, indented double-quoted strings process escape

sequences, and indented single-quoted strings ignore escape sequences. Escape

sequence processing takes place after unindentation. The unindentation

algorithm does not take escape-sequence produced whitespace or newlines into

account.



Strings prefixed with `x` are shell expanded1.27.0:



```justfile

foobar := x'~/$FOO/${BAR}'

```



| Value | Replacement |

|------|-------------|

| `$VAR` | value of environment variable `VAR` |

| `${VAR}` | value of environment variable `VAR` |

| `${VAR:-DEFAULT}` | value of environment variable `VAR`, or `DEFAULT` if `VAR` is not set |

| Leading `~` | path to current user's home directory |

| Leading `~USER` | path to `USER`'s home directory |



This expansion is performed at compile time, so variables from `.env` files and

exported `just` variables cannot be used. However, this allows shell expanded

strings to be used in places like settings and import paths, which cannot

depend on `just` variables and `.env` files.



### Ignoring Errors



Normally, if a command returns a non-zero exit status, execution will stop. To

continue execution after a command, even if it fails, prefix the command with

`-`:



```just

foo:

  -cat foo

  echo 'Done!'

```



```console

$ just foo

cat foo

cat: foo: No such file or directory

echo 'Done!'

Done!

```



### Functions



`just` provides a few built-in functions that might be useful when writing

recipes.



All functions ending in `_directory` can be abbreviated to `_dir`. So

`home_directory()` can also be written as `home_dir()`. In addition,

`invocation_directory_native()` can be abbreviated to

`invocation_dir_native()`.



#### System Information



- `arch()` — Instruction set architecture. Possible values are: `"aarch64"`,

  `"arm"`, `"asmjs"`, `"hexagon"`, `"mips"`, `"msp430"`, `"powerpc"`,

  `"powerpc64"`, `"s390x"`, `"sparc"`, `"wasm32"`, `"x86"`, `"x86_64"`, and

  `"xcore"`.

- `num_cpus()`1.15.0 - Number of logical CPUs.

- `os()` — Operating system. Possible values are: `"android"`, `"bitrig"`,

  `"dragonfly"`, `"emscripten"`, `"freebsd"`, `"haiku"`, `"ios"`, `"linux"`,

  `"macos"`, `"netbsd"`, `"openbsd"`, `"solaris"`, and `"windows"`.

- `os_family()` — Operating system family; possible values are: `"unix"` and

  `"windows"`.



For example:



```just

system-info:

  @echo "This is an {{arch()}} machine".

```



```console

$ just system-info

This is an x86_64 machine

```



The `os_family()` function can be used to create cross-platform `justfile`s

that work on various operating systems. For an example, see

[cross-platform.just](https://github.com/casey/just/blob/master/examples/cross-platform.just)

file.



#### External Commands



- `shell(command, args...)`1.27.0 returns the standard output of shell script

  `command` with zero or more positional arguments `args`. The shell used to

  interpret `command` is the same shell that is used to evaluate recipe lines,

  and can be changed with `set shell := […]`.



  `command` is passed as the first argument, so if the command is `'echo $@'`,

  the full command line, with the default shell command `shell -cu` and `args`

  `'foo'` and `'bar'` will be:



  ```

  'shell' '-cu' 'echo $@' 'echo $@' 'foo' 'bar'

  ```



  This is so that `$@` works as expected, and `$1` refers to the first

  argument. `$@` does not include the first positional argument, which is

  expected to be the name of the program being run.



```just

# arguments can be variables or expressions

file := '/sys/class/power_supply/BAT0/status'

bat0stat := shell('cat $1', file)



# commands can be variables or expressions

command := 'wc -l'

output := shell(command + ' "$1"', 'main.c')



# arguments referenced by the shell command must be used

empty := shell('echo', 'foo')

full := shell('echo $1', 'foo')

error := shell('echo $1')

```



```just

# Using python as the shell. Since `python -c` sets `sys.argv[0]` to `'-c'`,

# the first "real" positional argument will be `sys.argv[2]`.

set shell := ["python3", "-c"]

olleh := shell('import sys; print(sys.argv[2][::-1])', 'hello')

```



#### Environment Variables



- `env_var(key)` — Retrieves the environment variable with name `key`, aborting

  if it is not present.



```just

home_dir := env_var('HOME')



test:

  echo "{{home_dir}}"

```



```console

$ just

/home/user1

```



- `env_var_or_default(key, default)` — Retrieves the environment variable with

  name `key`, returning `default` if it is not present.

- `env(key)`1.15.0 — Alias for `env_var(key)`.

- `env(key, default)`1.15.0 — Alias for `env_var_or_default(key, default)`.



#### Invocation Information



- `is_dependency()` - Returns the string `true` if the current recipe is being

  run as a dependency of another recipe, rather than being run directly,

  otherwise returns the string `false`.



#### Invocation Directory



- `invocation_directory()` - Retrieves the absolute path to the current

  directory when `just` was invoked, before  `just` changed it (chdir'd) prior

  to executing commands. On Windows, `invocation_directory()` uses `cygpath` to

  convert the invocation directory to a Cygwin-compatible `/`-separated path.

  Use `invocation_directory_native()` to return the verbatim invocation

  directory on all platforms.



For example, to call `rustfmt` on files just under the "current directory"

(from the user/invoker's perspective), use the following rule:



```just

rustfmt:

  find {{invocation_directory()}} -name \*.rs -exec rustfmt {} \;

```



Alternatively, if your command needs to be run from the current directory, you

could use (e.g.):



```just

build:

  cd {{invocation_directory()}}; ./some_script_that_needs_to_be_run_from_here

```



- `invocation_directory_native()` - Retrieves the absolute path to the current

  directory when `just` was invoked, before  `just` changed it (chdir'd) prior

  to executing commands.



#### Justfile and Justfile Directory



- `justfile()` - Retrieves the path of the current `justfile`.



- `justfile_directory()` - Retrieves the path of the parent directory of the

  current `justfile`.



For example, to run a command relative to the location of the current

`justfile`:



```just

script:

  {{justfile_directory()}}/scripts/some_script

```



#### Source and Source Directory



- `source_file()`1.27.0 - Retrieves the path of the current source file.



- `source_directory()`1.27.0 - Retrieves the path of the parent directory of the

  current source file.



`source_file()` and `source_directory()` behave the same as `justfile()` and

`justfile_directory()` in the root `justfile`, but will return the path and

directory, respectively, of the current `import` or `mod` source file when

called from within an import or submodule.



#### Just Executable



- `just_executable()` - Absolute path to the `just` executable.



For example:



```just

executable:

  @echo The executable is at: {{just_executable()}}

```



```console

$ just

The executable is at: /bin/just

```



#### Just Process ID



- `just_pid()` - Process ID of the `just` executable.



For example:



```just

pid:

  @echo The process ID is: {{ just_pid() }}

```



```console

$ just

The process ID is: 420

```



#### String Manipulation



- `append(suffix, s)`1.27.0 Append `suffix` to whitespace-separated

  strings in `s`. `append('/src', 'foo bar baz')` → `'foo/src bar/src baz/src'`

- `prepend(prefix, s)`1.27.0 Prepend `prefix` to

  whitespace-separated strings in `s`. `prepend('src/', 'foo bar baz')` →

  `'src/foo src/bar src/baz'`

- `encode_uri_component(s)`1.27.0 - Percent-encode characters in `s`

  except `[A-Za-z0-9_.!~*'()-]`, matching the behavior of the

  [JavaScript `encodeURIComponent` function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent).

- `quote(s)` - Replace all single quotes with `'\''` and prepend and append

  single quotes to `s`. This is sufficient to escape special characters for

  many shells, including most Bourne shell descendants.

- `replace(s, from, to)` - Replace all occurrences of `from` in `s` to `to`.

- `replace_regex(s, regex, replacement)` - Replace all occurrences of `regex`

  in `s` to `replacement`. Regular expressions are provided by the

  [Rust `regex` crate](https://docs.rs/regex/latest/regex/). See the

  [syntax documentation](https://docs.rs/regex/latest/regex/#syntax) for usage

  examples. Capture groups are supported. The `replacement` string uses

  [Replacement string syntax](https://docs.rs/regex/latest/regex/struct.Regex.html#replacement-string-syntax).

- `trim(s)` - Remove leading and trailing whitespace from `s`.

- `trim_end(s)` - Remove trailing whitespace from `s`.

- `trim_end_match(s, pat)` - Remove suffix of `s` matching `pat`.

- `trim_end_matches(s, pat)` - Repeatedly remove suffixes of `s` matching

  `pat`.

- `trim_start(s)` - Remove leading whitespace from `s`.

- `trim_start_match(s, pat)` - Remove prefix of `s` matching `pat`.

- `trim_start_matches(s, pat)` - Repeatedly remove prefixes of `s` matching

  `pat`.



#### Case Conversion



- `capitalize(s)`1.7.0 - Convert first character of `s` to uppercase

  and the rest to lowercase.

- `kebabcase(s)`1.7.0 - Convert `s` to `kebab-case`.

- `lowercamelcase(s)`1.7.0 - Convert `s` to `lowerCamelCase`.

- `lowercase(s)` - Convert `s` to lowercase.

- `shoutykebabcase(s)`1.7.0 - Convert `s` to `SHOUTY-KEBAB-CASE`.

- `shoutysnakecase(s)`1.7.0 - Convert `s` to `SHOUTY_SNAKE_CASE`.

- `snakecase(s)`1.7.0 - Convert `s` to `snake_case`.

- `titlecase(s)`1.7.0 - Convert `s` to `Title Case`.

- `uppercamelcase(s)`1.7.0 - Convert `s` to `UpperCamelCase`.

- `uppercase(s)` - Convert `s` to uppercase.



#### Path Manipulation



##### Fallible



- `absolute_path(path)` - Absolute path to relative `path` in the working

  directory. `absolute_path("./bar.txt")` in directory `/foo` is

  `/foo/bar.txt`.

- `canonicalize(path)`1.24.0 - Canonicalize `path` by resolving symlinks and removing

  `.`, `..`, and extra `/`s where possible.

- `extension(path)` - Extension of `path`. `extension("/foo/bar.txt")` is

  `txt`.

- `file_name(path)` - File name of `path` with any leading directory components

  removed. `file_name("/foo/bar.txt")` is `bar.txt`.

- `file_stem(path)` - File name of `path` without extension.

  `file_stem("/foo/bar.txt")` is `bar`.

- `parent_directory(path)` - Parent directory of `path`.

  `parent_directory("/foo/bar.txt")` is `/foo`.

- `without_extension(path)` - `path` without extension.

  `without_extension("/foo/bar.txt")` is `/foo/bar`.



These functions can fail, for example if a path does not have an extension,

which will halt execution.



##### Infallible



- `clean(path)` - Simplify `path` by removing extra path separators,

  intermediate `.` components, and `..` where possible. `clean("foo//bar")` is

  `foo/bar`, `clean("foo/..")` is `.`, `clean("foo/./bar")` is `foo/bar`.

- `join(a, b…)` - *This function uses `/` on Unix and `\` on Windows, which can

  be lead to unwanted behavior. The `/` operator, e.g., `a / b`, which always

  uses `/`, should be considered as a replacement unless `\`s are specifically

  desired on Windows.* Join path `a` with path `b`. `join("foo/bar", "baz")` is

  `foo/bar/baz`. Accepts two or more arguments.



#### Filesystem Access



- `path_exists(path)` - Returns `true` if the path points at an existing entity

  and `false` otherwise. Traverses symbolic links, and returns `false` if the

  path is inaccessible or points to a broken symlink.



##### Error Reporting



- `error(message)` - Abort execution and report error `message` to user.



#### UUID and Hash Generation



- `blake3(string)`1.25.0 - Return [BLAKE3] hash of `string` as hexadecimal string.

- `blake3_file(path)`1.25.0 - Return [BLAKE3] hash of file at `path` as hexadecimal

  string.

- `sha256(string)` - Return the SHA-256 hash of `string` as hexadecimal string.

- `sha256_file(path)` - Return SHA-256 hash of file at `path` as hexadecimal

  string.

- `uuid()` - Generate a random version 4 UUID.



[BLAKE3]: https://github.com/BLAKE3-team/BLAKE3/



#### Random



- `choose(n, alphabet)`1.27.0 - Generate a string of `n` randomly

  selected characters from `alphabet`, which may not contain repeated

  characters. For example, `choose('64', HEX)` will generate a random

  64-character lowercase hex string.



#### Datetime



- `datetime(format)`1.30.0 - Return local time with `format`.

- `datetime_utc(format)`1.30.0 - Return UTC time with `format`.



The arguments to `datetime` and `datetime_utc` are `strftime`-style format

strings, see the

[`chrono` library docs](https://docs.rs/chrono/latest/chrono/format/strftime/index.html)

for details.



#### Semantic Versions



- `semver_matches(version, requirement)`1.16.0 - Check whether a

  [semantic `version`](https://semver.org), e.g., `"0.1.0"` matches a

  `requirement`, e.g., `">=0.1.0"`, returning `"true"` if so and `"false"`

  otherwise.



##### XDG Directories1.23.0



These functions return paths to user-specific directories for things like

configuration, data, caches, executables, and the user's home directory. These

functions follow the

[XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html),

and are implemented with the

[`dirs`](https://docs.rs/dirs/latest/dirs/index.html) crate.



- `cache_directory()` - The user-specific cache directory.

- `config_directory()` - The user-specific configuration directory.

- `config_local_directory()` - The local user-specific configuration directory.

- `data_directory()` - The user-specific data directory.

- `data_local_directory()` - The local user-specific data directory.

- `executable_directory()` - The user-specific executable directory.

- `home_directory()` - The user's home directory.



### Constants



A number of constants are predefined:



| Name | Value |

|------|-------------|

| `HEX`1.27.0 | `"0123456789abcdef"` |

| `HEXLOWER`1.27.0 | `"0123456789abcdef"` |

| `HEXUPPER`1.27.0 | `"0123456789ABCDEF"` |



```just

@foo:

  echo {{HEX}}

```



```console

$ just foo

0123456789abcdef

```



### Attributes



Recipes, `mod` statements, and aliases may be annotated with attributes that change their behavior.



| Name | Type | Description |

|------|------|-------------|

| `[confirm]`1.17.0 | recipe | Require confirmation prior to executing recipe. |

| `[confirm('PROMPT')]`1.23.0 | recipe | Require confirmation prior to executing recipe with a custom prompt. |

| `[doc('DOC')]`1.27.0 | module, recipe | Set recipe or module's [documentation comment](#documentation-comments) to `DOC`. |

| `[extension('EXT')]`1.32.0 | recipe | Set shebang recipe script's file extension to `EXT`. `EXT` should include a period if one is desired. |

| `[group('NAME')]`1.27.0 | module, recipe | Put recipe or module in in [group](#groups) `NAME`. |

| `[linux]`1.8.0 | recipe | Enable recipe on Linux. |

| `[macos]`1.8.0 | recipe | Enable recipe on MacOS. |

| `[no-cd]`1.9.0 | recipe | Don't change directory before executing recipe. |

| `[no-exit-message]`1.7.0 | recipe | Don't print an error message if recipe fails. |

| `[no-quiet]`1.23.0 | recipe | Override globally quiet recipes and always echo out the recipe. |

| `[positional-arguments]`1.29.0 | recipe | Turn on [positional arguments](#positional-arguments) for this recipe. |

| `[private]`1.10.0 | alias, recipe | Make recipe, alias, or variable private. See [Private Recipes](#private-recipes). |

| `[script]`1.33.0 | recipe | Execute recipe as script. See [script recipes](#script-recipes) for more details. |

| `[script(COMMAND)]`1.32.0 | recipe | Execute recipe as a script interpreted by `COMMAND`. See [script recipes](#script-recipes) for more details. |

| `[unix]`1.8.0 | recipe | Enable recipe on Unixes. (Includes MacOS). |

| `[windows]`1.8.0 | recipe | Enable recipe on Windows. |



A recipe can have multiple attributes, either on multiple lines:



```just

[no-cd]

[private]

foo:

    echo "foo"

```



Or separated by commas on a single line1.14.0:



```just

[no-cd, private]

foo:

    echo "foo"

```



#### Enabling and Disabling Recipes1.8.0



The `[linux]`, `[macos]`, `[unix]`, and `[windows]` attributes are

configuration attributes. By default, recipes are always enabled. A recipe with

one or more configuration attributes will only be enabled when one or more of

those configurations is active.



This can be used to write `justfile`s that behave differently depending on

which operating system they run on. The `run` recipe in this `justfile` will

compile and run `main.c`, using a different C compiler and using the correct

output binary name for that compiler depending on the operating system:



```just

[unix]

run:

  cc main.c

  ./a.out



[windows]

run:

  cl main.c

  main.exe

```



#### Disabling Changing Directory1.9.0



`just` normally executes recipes with the current directory set to the

directory that contains the `justfile`. This can be disabled using the

`[no-cd]` attribute. This can be used to create recipes which use paths

relative to the invocation directory, or which operate on the current

directory.



For example, this `commit` recipe:



```just

[no-cd]

commit file:

  git add {{file}}

  git commit

```



Can be used with paths that are relative to the current directory, because

`[no-cd]` prevents `just` from changing the current directory when executing

`commit`.



#### Requiring Confirmation for Recipes1.17.0



`just` normally executes all recipes unless there is an error. The `[confirm]`

attribute allows recipes require confirmation in the terminal prior to running.

This can be overridden by passing `--yes` to `just`, which will automatically

confirm any recipes marked by this attribute.



Recipes dependent on a recipe that requires confirmation will not be run if the

relied upon recipe is not confirmed, as well as recipes passed after any recipe

that requires confirmation.



```just

[confirm]

delete-all:

  rm -rf *

```



#### Custom Confirmation Prompt1.23.0



The default confirmation prompt can be overridden with `[confirm(PROMPT)]`:



```just

[confirm("Are you sure you want to delete everything?")]

delete-everything:

  rm -rf *

```



### Groups



Recipes and modules may be annotated with a group name:



```just

[group('lint')]

js-lint:

    echo 'Running JS linter…'



[group('rust recipes')]

[group('lint')]

rust-lint:

    echo 'Running Rust linter…'



[group('lint')]

cpp-lint:

  echo 'Running C++ linter…'



# not in any group

email-everyone:

    echo 'Sending mass email…'

```



Recipes are listed by group:



```

$ just --list

Available recipes:

    email-everyone # not in any group



    [lint]

    cpp-lint

    js-lint

    rust-lint



    [rust recipes]

    rust-lint

```



`just --list --unsorted` prints recipes in their justfile order within each group:



```

$ just --list --unsorted

Available recipes:

    (no group)

    email-everyone # not in any group



    [lint]

    js-lint

    rust-lint

    cpp-lint



    [rust recipes]

    rust-lint

```



Groups can be listed with `--groups`:



```

$ just --groups

Recipe groups:

  lint

  rust recipes

```



Use `just --groups --unsorted` to print groups in their justfile order.



### Command Evaluation Using Backticks



Backticks can be used to store the result of commands:



```just

localhost := `dumpinterfaces | cut -d: -f2 | sed 's/\/.*//' | sed 's/ //g'`



serve:

  ./serve {{localhost}} 8080

```



Indented backticks, delimited by three backticks, are de-indented in the same

manner as indented strings:



````just

# This backtick evaluates the command `echo foo\necho bar\n`, which produces the value `foo\nbar\n`.

stuff := ```

    echo foo

    echo bar

  ```

````



See the [Strings](#strings) section for details on unindenting.



Backticks may not start with `#!`. This syntax is reserved for a future

upgrade.



### Conditional Expressions



`if`/`else` expressions evaluate different branches depending on if two

expressions evaluate to the same value:



```just

foo := if "2" == "2" { "Good!" } else { "1984" }



bar:

  @echo "{{foo}}"

```



```console

$ just bar

Good!

```



It is also possible to test for inequality:



```just

foo := if "hello" != "goodbye" { "xyz" } else { "abc" }



bar:

  @echo {{foo}}

```



```console

$ just bar

xyz

```



And match against regular expressions:



```just

foo := if "hello" =~ 'hel+o' { "match" } else { "mismatch" }



bar:

  @echo {{foo}}

```



```console

$ just bar

match

```



Regular expressions are provided by the

[regex crate](https://github.com/rust-lang/regex), whose syntax is documented on

[docs.rs](https://docs.rs/regex/1.5.4/regex/#syntax). Since regular expressions

commonly use backslash escape sequences, consider using single-quoted string

literals, which will pass slashes to the regex parser unmolested.



Conditional expressions short-circuit, which means they only evaluate one of

their branches. This can be used to make sure that backtick expressions don't

run when they shouldn't.



```just

foo := if env_var("RELEASE") == "true" { `get-something-from-release-database` } else { "dummy-value" }

```



Conditionals can be used inside of recipes:



```just

bar foo:

  echo {{ if foo == "bar" { "hello" } else { "goodbye" } }}

```



Note the space after the final `}`! Without the space, the interpolation will

be prematurely closed.



Multiple conditionals can be chained:



```just

foo := if "hello" == "goodbye" {

  "xyz"

} else if "a" == "a" {

  "abc"

} else {

  "123"

}



bar:

  @echo {{foo}}

```



```console

$ just bar

abc

```



### Stopping execution with error



Execution can be halted with the `error` function. For example:



```just

foo := if "hello" == "goodbye" {

  "xyz"

} else if "a" == "b" {

  "abc"

} else {

  error("123")

}

```



Which produce the following error when run:



```

error: Call to function `error` failed: 123

   |

16 |   error("123")

```



### Setting Variables from the Command Line



Variables can be overridden from the command line.



```just

os := "linux"



test: build

  ./test --test {{os}}



build:

  ./build {{os}}

```



```console

$ just

./build linux

./test --test linux

```



Any number of arguments of the form `NAME=VALUE` can be passed before recipes:



```console

$ just os=plan9

./build plan9

./test --test plan9

```



Or you can use the `--set` flag:



```console

$ just --set os bsd

./build bsd

./test --test bsd

```



### Getting and Setting Environment Variables



#### Exporting `just` Variables



Assignments prefixed with the `export` keyword will be exported to recipes as

environment variables:



```just

export RUST_BACKTRACE := "1"



test:

  # will print a stack trace if it crashes

  cargo test

```



Parameters prefixed with a `$` will be exported as environment variables:



```just

test $RUST_BACKTRACE="1":

  # will print a stack trace if it crashes

  cargo test

```



Exported variables and parameters are not exported to backticks in the same scope.



```just

export WORLD := "world"

# This backtick will fail with "WORLD: unbound variable"

BAR := `echo hello $WORLD`

```



```just

# Running `just a foo` will fail with "A: unbound variable"

a $A $B=`echo $A`:

  echo $A $B

```



When [export](#export) is set, all `just` variables are exported as environment

variables.



#### Unexporting Environment Variables1.29.0



Environment variables can be unexported with the `unexport keyword`:



```just

unexport FOO



@foo:

  echo $FOO

```



```

$ export FOO=bar

$ just foo

sh: FOO: unbound variable

```



#### Getting Environment Variables from the environment



Environment variables from the environment are passed automatically to the

recipes.



```just

print_home_folder:

  echo "HOME is: '${HOME}'"

```



```console

$ just

HOME is '/home/myuser'

```



#### Setting `just` Variables from Environment Variables



Environment variables can be propagated to `just` variables using the functions

`env_var()` and `env_var_or_default()`. See

[environment-variables](#environment-variables).



### Recipe Parameters



Recipes may have parameters. Here recipe `build` has a parameter called

`target`:



```just

build target:

  @echo 'Building {{target}}…'

  cd {{target}} && make

```



To pass arguments on the command line, put them after the recipe name:



```console

$ just build my-awesome-project

Building my-awesome-project…

cd my-awesome-project && make

```



To pass arguments to a dependency, put the dependency in parentheses along with

the arguments:



```just

default: (build "main")



build target:

  @echo 'Building {{target}}…'

  cd {{target}} && make

```



Variables can also be passed as arguments to dependencies:



```just

target := "main"



_build version:

  @echo 'Building {{version}}…'

  cd {{version}} && make



build: (_build target)

```



A command's arguments can be passed to dependency by putting the dependency in

parentheses along with the arguments:



```just

build target:

  @echo "Building {{target}}…"



push target: (build target)

  @echo 'Pushing {{target}}…'

```



Parameters may have default values:



```just

default := 'all'



test target tests=default:

  @echo 'Testing {{target}}:{{tests}}…'

  ./test --tests {{tests}} {{target}}

```



Parameters with default values may be omitted:



```console

$ just test server

Testing server:all…

./test --tests all server

```



Or supplied:



```console

$ just test server unit

Testing server:unit…

./test --tests unit server

```



Default values may be arbitrary expressions, but concatenations or path joins

must be parenthesized:



```just

arch := "wasm"



test triple=(arch + "-unknown-unknown") input=(arch / "input.dat"):

  ./test {{triple}}

```



The last parameter of a recipe may be variadic, indicated with either a `+` or

a `*` before the argument name:



```just

backup +FILES:

  scp {{FILES}} [email protected]:

```



Variadic parameters prefixed with `+` accept _one or more_ arguments and expand

to a string containing those arguments separated by spaces:



```console

$ just backup FAQ.md GRAMMAR.md

scp FAQ.md GRAMMAR.md [email protected]:

FAQ.md                  100% 1831     1.8KB/s   00:00

GRAMMAR.md              100% 1666     1.6KB/s   00:00

```



Variadic parameters prefixed with `*` accept _zero or more_ arguments and

expand to a string containing those arguments separated by spaces, or an empty

string if no arguments are present:



```just

commit MESSAGE *FLAGS:

  git commit {{FLAGS}} -m "{{MESSAGE}}"

```



Variadic parameters can be assigned default values. These are overridden by

arguments passed on the command line:



```just

test +FLAGS='-q':

  cargo test {{FLAGS}}

```



`{{…}}` substitutions may need to be quoted if they contain spaces. For

example, if you have the following recipe:



```just

search QUERY:

  lynx https://www.google.com/?q={{QUERY}}

```



And you type:



```console

$ just search "cat toupee"

```



`just` will run the command `lynx https://www.google.com/?q=cat toupee`, which

will get parsed by `sh` as `lynx`, `https://www.google.com/?q=cat`, and

`toupee`, and not the intended `lynx` and `https://www.google.com/?q=cat toupee`.



You can fix this by adding quotes:



```just

search QUERY:

  lynx 'https://www.google.com/?q={{QUERY}}'

```



Parameters prefixed with a `$` will be exported as environment variables:



```just

foo $bar:

  echo $bar

```



### Dependencies



Dependencies run before recipes that depend on them:



```just

a: b

  @echo A



b:

  @echo B

```



```

$ just a

B

A

```



In a given invocation of `just`, a recipe with the same arguments will only run

once, regardless of how many times it appears in the command-line invocation,

or how many times it appears as a dependency:



```just

a:

  @echo A



b: a

  @echo B



c: a

  @echo C

```



```

$ just a a a a a

A

$ just b c

A

B

C

```



Multiple recipes may depend on a recipe that performs some kind of setup, and

when those recipes run, that setup will only be performed once:



```just

build:

  cc main.c



test-foo: build

  ./a.out --test foo



test-bar: build

  ./a.out --test bar

```



```

$ just test-foo test-bar

cc main.c

./a.out --test foo

./a.out --test bar

```



Recipes in a given run are only skipped when they receive the same arguments:



```just

build:

  cc main.c



test TEST: build

  ./a.out --test {{TEST}}

```



```

$ just test foo test bar

cc main.c

./a.out --test foo

./a.out --test bar

```



#### Running Recipes at the End of a Recipe



Normal dependencies of a recipes always run before a recipe starts. That is to

say, the dependee always runs before the depender. These dependencies are

called "prior dependencies".



A recipe can also have subsequent dependencies, which run immediately after the

recipe and are introduced with an `&&`:



```just

a:

  echo 'A!'



b: a && c d

  echo 'B!'



c:

  echo 'C!'



d:

  echo 'D!'

```



…running _b_ prints:



```console

$ just b

echo 'A!'

A!

echo 'B!'

B!

echo 'C!'

C!

echo 'D!'

D!

```



#### Running Recipes in the Middle of a Recipe



`just` doesn't support running recipes in the middle of another recipe, but you

can call `just` recursively in the middle of a recipe. Given the following

`justfile`:



```just

a:

  echo 'A!'



b: a

  echo 'B start!'

  just c

  echo 'B end!'



c:

  echo 'C!'

```



…running _b_ prints:



```console

$ just b

echo 'A!'

A!

echo 'B start!'

B start!

echo 'C!'

C!

echo 'B end!'

B end!

```



This has limitations, since recipe `c` is run with an entirely new invocation

of `just`: Assignments will be recalculated, dependencies might run twice, and

command line arguments will not be propagated to the child `just` process.



### Shebang Recipes



Recipes that start with `#!` are called shebang recipes, and are executed by

saving the recipe body to a file and running it. This lets you write recipes in

different languages:



```just

polyglot: python js perl sh ruby nu



python:

  #!/usr/bin/env python3

  print('Hello from python!')



js:

  #!/usr/bin/env node

  console.log('Greetings from JavaScript!')



perl:

  #!/usr/bin/env perl

  print "Larry Wall says Hi!\n";



sh:

  #!/usr/bin/env sh

  hello='Yo'

  echo "$hello from a shell script!"



nu:

  #!/usr/bin/env nu

  let hello = 'Hola'

  echo $"($hello) from a nushell script!"



ruby:

  #!/usr/bin/env ruby

  puts "Hello from ruby!"

```



```console

$ just polyglot

Hello from python!

Greetings from JavaScript!

Larry Wall says Hi!

Yo from a shell script!

Hola from a nushell script!

Hello from ruby!

```



On Unix-like operating systems, including Linux and MacOS, shebang recipes are

executed by saving the recipe body to a file in a temporary directory, marking

the file as executable, and executing it. The OS then parses the shebang line

into a command line and invokes it, including the path to the file. For

example, if a recipe starts with `#!/usr/bin/env bash`, the final command that

the OS runs will be something like `/usr/bin/env bash

/tmp/PATH_TO_SAVED_RECIPE_BODY`.



Shebang line splitting is operating system dependent. When passing a command

with arguments, you may need to tell `env` to split them explicitly by using

the `-S` flag:



```just

run:

  #!/usr/bin/env -S bash -x

  ls

```



Windows does not support shebang lines. On Windows, `just` splits the shebang

line into a command and arguments, saves the recipe body to a file, and invokes

the split command and arguments, adding the path to the saved recipe body as

the final argument. For example, on Windows, if a recipe starts with `#! py`,

the final command the OS runs will be something like

`py C:\Temp\PATH_TO_SAVED_RECIPE_BODY`.



### Script Recipes



Recipes with a `[script(COMMAND)]`1.32.0 attribute are run as

scripts interpreted by `COMMAND`. This avoids some of the issues with shebang

recipes, such as the use of `cygpath` on Windows, the need to use

`/usr/bin/env`, and inconsistences in shebang line splitting across Unix OSs.



Recipes with an empty `[script]` attribute are executed with the value of

`set script-interpreter := […]`1.33.0, defaulting to `sh -eu`.



The body of the recipe is evaluated, written to disk in the temporary

directory, and run by passing its path as an argument to `COMMAND`.



The `[script(…)]` attribute is unstable, so you'll need to use `set unstable`,

set the `JUST_UNSTABLE` environment variable, or pass `--unstable` on the

command line.



### Safer Bash Shebang Recipes



If you're writing a `bash` shebang recipe, consider adding `set -euxo

pipefail`:



```just

foo:

  #!/usr/bin/env bash

  set -euxo pipefail

  hello='Yo'

  echo "$hello from Bash!"

```



It isn't strictly necessary, but `set -euxo pipefail` turns on a few useful

features that make `bash` shebang recipes behave more like normal, linewise

`just` recipe:



- `set -e` makes `bash` exit if a command fails.



- `set -u` makes `bash` exit if a variable is undefined.



- `set -x` makes `bash` print each script line before it's run.



- `set -o pipefail` makes `bash` exit if a command in a pipeline fails. This is

  `bash`-specific, so isn't turned on in normal linewise `just` recipes.



Together, these avoid a lot of shell scripting gotchas.



#### Shebang Recipe Execution on Windows



On Windows, shebang interpreter paths containing a `/` are translated from

Unix-style paths to Windows-style paths using `cygpath`, a utility that ships

with [Cygwin](http://www.cygwin.com).



For example, to execute this recipe on Windows:



```just

echo:

  #!/bin/sh

  echo "Hello!"

```



The interpreter path `/bin/sh` will be translated to a Windows-style path using

`cygpath` before being executed.



If the interpreter path does not contain a `/` it will be executed without

being translated. This is useful if `cygpath` is not available, or you wish to

pass a Windows-style path to the interpreter.



### Setting Variables in a Recipe



Recipe lines are interpreted by the shell, not `just`, so it's not possible to

set `just` variables in the middle of a recipe:



```mf

foo:

  x := "hello" # This doesn't work!

  echo {{x}}

```



It is possible to use shell variables, but there's another problem. Every

recipe line is run by a new shell instance, so variables set in one line won't

be set in the next:



```just

foo:

  x=hello && echo $x # This works!

  y=bye

  echo $y            # This doesn't, `y` is undefined here!

```



The best way to work around this is to use a shebang recipe. Shebang recipe

bodies are extracted and run as scripts, so a single shell instance will run

the whole thing:



```just

foo:

  #!/usr/bin/env bash

  set -euxo pipefail

  x=hello

  echo $x

```



### Sharing Environment Variables Between Recipes



Each line of each recipe is executed by a fresh shell, so it is not possible to

share environment variables between recipes.



#### Using Python Virtual Environments



Some tools, like [Python's venv](https://docs.python.org/3/library/venv.html),

require loading environment variables in order to work, making them challenging

to use with `just`. As a workaround, you can execute the virtual environment

binaries directly:



```just

venv:

  [ -d foo ] || python3 -m venv foo



run: venv

  ./foo/bin/python3 main.py

```



### Changing the Working Directory in a Recipe



Each recipe line is executed by a new shell, so if you change the working

directory on one line, it won't have an effect on later lines:



```just

foo:

  pwd    # This `pwd` will print the same directory…

  cd bar

  pwd    # …as this `pwd`!

```



There are a couple ways around this. One is to call `cd` on the same line as

the command you want to run:



```just

foo:

  cd bar && pwd

```



The other is to use a shebang recipe. Shebang recipe bodies are extracted and

run as scripts, so a single shell instance will run the whole thing, and thus a

`pwd` on one line will affect later lines, just like a shell script:



```just

foo:

  #!/usr/bin/env bash

  set -euxo pipefail

  cd bar

  pwd

```



### Indentation



Recipe lines can be indented with spaces or tabs, but not a mix of both. All of

a recipe's lines must have the same type of indentation, but different recipes

in the same `justfile` may use different indentation.



Each recipe must be indented at least one level from the `recipe-name` but

after that may be further indented.



Here's a justfile with a recipe indented with spaces, represented as `·`, and

tabs, represented as `→`.



```justfile

set windows-shell := ["pwsh", "-NoLogo", "-NoProfileLoadTime", "-Command"]



set ignore-comments



list-space directory:

··#!pwsh

··foreach ($item in $(Get-ChildItem {{directory}} )) {

····echo $item.Name

··}

··echo ""



# indentation nesting works even when newlines are escaped

list-tab directory:

→ @foreach ($item in $(Get-ChildItem {{directory}} )) { \

→ → echo $item.Name \

→ }

→ @echo ""

```



```pwsh

PS > just list-space ~

Desktop

Documents

Downloads



PS > just list-tab ~

Desktop

Documents

Downloads

```



### Multi-Line Constructs



Recipes without an initial shebang are evaluated and run line-by-line, which

means that multi-line constructs probably won't do what you want.



For example, with the following `justfile`:



```mf

conditional:

  if true; then

    echo 'True!'

  fi

```



The extra leading whitespace before the second line of the `conditional` recipe

will produce a parse error:



```console

$ just conditional

error: Recipe line has extra leading whitespace

  |

3 |         echo 'True!'

  |     ^^^^^^^^^^^^^^^^

```



To work around this, you can write conditionals on one line, escape newlines

with slashes, or add a shebang to your recipe. Some examples of multi-line

constructs are provided for reference.



#### `if` statements



```just

conditional:

  if true; then echo 'True!'; fi

```



```just

conditional:

  if true; then \

    echo 'True!'; \

  fi

```



```just

conditional:

  #!/usr/bin/env sh

  if true; then

    echo 'True!'

  fi

```



#### `for` loops



```just

for:

  for file in `ls .`; do echo $file; done

```



```just

for:

  for file in `ls .`; do \

    echo $file; \

  done

```



```just

for:

  #!/usr/bin/env sh

  for file in `ls .`; do

    echo $file

  done

```



#### `while` loops



```just

while:

  while `server-is-dead`; do ping -c 1 server; done

```



```just

while:

  while `server-is-dead`; do \

    ping -c 1 server; \

  done

```



```just

while:

  #!/usr/bin/env sh

  while `server-is-dead`; do

    ping -c 1 server

  done

```



#### Outside Recipe Bodies



Parenthesized expressions can span multiple lines:



```just

abc := ('a' +

        'b'

         + 'c')



abc2 := (

  'a' +

  'b' +

  'c'

)



foo param=('foo'

      + 'bar'

    ):

  echo {{param}}



bar: (foo

        'Foo'

     )

  echo 'Bar!'

```



Lines ending with a backslash continue on to the next line as if the lines were

joined by whitespace1.15.0:



```just

a := 'foo' + \

     'bar'



foo param1 \

  param2='foo' \

  *varparam='': dep1 \

                (dep2 'foo')

  echo {{param1}} {{param2}} {{varparam}}



dep1: \

    # this comment is not part of the recipe body

  echo 'dep1'



dep2 \

  param:

    echo 'Dependency with parameter {{param}}'

```



Backslash line continuations can also be used in interpolations. The line

following the backslash must be indented.



```just

recipe:

  echo '{{ \

  "This interpolation " + \

    "has a lot of text." \

  }}'

  echo 'back to recipe body'

```



### Command Line Options



`just` supports a number of useful command line options for listing, dumping,

and debugging recipes and variables:



```console

$ just --list

Available recipes:

  js

  perl

  polyglot

  python

  ruby

$ just --show perl

perl:

  #!/usr/bin/env perl

  print "Larry Wall says Hi!\n";

$ just --show polyglot

polyglot: python js perl sh ruby

```



Some command-line options can be set with environment variables. For example:



```console

$ export JUST_UNSTABLE=1

$ just

```



Is equivalent to:



```console

$ just --unstable

```



Consult `just --help` to see which options can be set from environment

variables.



### Private Recipes



Recipes and aliases whose name starts with a `_` are omitted from `just --list`:



```just

test: _test-helper

  ./bin/test



_test-helper:

  ./bin/super-secret-test-helper-stuff

```



```console

$ just --list

Available recipes:

    test

```



And from `just --summary`:



```console

$ just --summary

test

```



The `[private]` attribute1.10.0 may also be used to hide recipes or

aliases without needing to change the name:



```just

[private]

foo:



[private]

alias b := bar



bar:

```



```console

$ just --list

Available recipes:

    bar

```



This is useful for helper recipes which are only meant to be used as

dependencies of other recipes.



### Quiet Recipes



A recipe name may be prefixed with `@` to invert the meaning of `@` before each

line:



```just

@quiet:

  echo hello

  echo goodbye

  @# all done!

```



Now only the lines starting with `@` will be echoed:



```console

$ just quiet

hello

goodbye

# all done!

```



All recipes in a Justfile can be made quiet with `set quiet`:



```just

set quiet



foo:

  echo "This is quiet"



@foo2:

  echo "This is also quiet"

```



The `[no-quiet]` attribute overrides this setting:



```just

set quiet



foo:

  echo "This is quiet"



[no-quiet]

foo2:

  echo "This is not quiet"

```



Shebang recipes are quiet by default:



```just

foo:

  #!/usr/bin/env bash

  echo 'Foo!'

```



```console

$ just foo

Foo!

```



Adding `@` to a shebang recipe name makes `just` print the recipe before

executing it:



```just

@bar:

  #!/usr/bin/env bash

  echo 'Bar!'

```



```console

$ just bar

#!/usr/bin/env bash

echo 'Bar!'

Bar!

```



`just` normally prints error messages when a recipe line fails. These error

messages can be suppressed using the `[no-exit-message]`1.7.0

attribute. You may find this especially useful with a recipe that wraps a tool:



```just

git *args:

    @git {{args}}

```



```console

$ just git status

fatal: not a git repository (or any of the parent directories): .git

error: Recipe `git` failed on line 2 with exit code 128

```



Add the attribute to suppress the exit error message when the tool exits with a

non-zero code:



```just

[no-exit-message]

git *args:

    @git {{args}}

```



```console

$ just git status

fatal: not a git repository (or any of the parent directories): .git

```



### Selecting Recipes to Run With an Interactive Chooser



The `--choose` subcommand makes `just` invoke a chooser to select which recipes

to run. Choosers should read lines containing recipe names from standard input

and print one or more of those names separated by spaces to standard output.



Because there is currently no way to run a recipe that requires arguments with

`--choose`, such recipes will not be given to the chooser. Private recipes and

aliases are also skipped.



The chooser can be overridden with the `--chooser` flag. If `--chooser` is not

given, then `just` first checks if `$JUST_CHOOSER` is set. If it isn't, then

the chooser defaults to `fzf`, a popular fuzzy finder.



Arguments can be included in the chooser, i.e. `fzf --exact`.



The chooser is invoked in the same way as recipe lines. For example, if the

chooser is `fzf`, it will be invoked with `sh -cu 'fzf'`, and if the shell, or

the shell arguments are overridden, the chooser invocation will respect those

overrides.



If you'd like `just` to default to selecting recipes with a chooser, you can

use this as your default recipe:



```just

default:

  @just --choose

```



### Invoking `justfile`s in Other Directories



If the first argument passed to `just` contains a `/`, then the following

occurs:



1.  The argument is split at the last `/`.



2.  The part before the last `/` is treated as a directory. `just` will start

    its search for the `justfile` there, instead of in the current directory.



3.  The part after the last slash is treated as a normal argument, or ignored

    if it is empty.



This may seem a little strange, but it's useful if you wish to run a command in

a `justfile` that is in a subdirectory.



For example, if you are in a directory which contains a subdirectory named

`foo`, which contains a `justfile` with the recipe `build`, which is also the

default recipe, the following are all equivalent:



```console

$ (cd foo && just build)

$ just foo/build

$ just foo/

```



Additional recipes after the first are sought in the same `justfile`. For

example, the following are both equivalent:



```console

$ just foo/a b

$ (cd foo && just a b)

```



And will both invoke recipes `a` and `b` in `foo/justfile`.



### Imports



One `justfile` can include the contents of another using `import` statements.



If you have the following `justfile`:



```mf

import 'foo/bar.just'



a: b

  @echo A

```



And the following text in `foo/bar.just`:



```just

b:

  @echo B

```



`foo/bar.just` will be included in `justfile` and recipe `b` will be defined:



```console

$ just b

B

$ just a

B

A

```



The `import` path can be absolute or relative to the location of the justfile

containing it. A leading `~/` in the import path is replaced with the current

users home directory.



Justfiles are insensitive to order, so included files can reference variables

and recipes defined after the `import` statement.



Imported files can themselves contain `import`s, which are processed

recursively.



When `allow-duplicate-recipes` is set, recipes in parent modules override

recipes in imports. In a similar manner, when `allow-duplicate-variables` is

set, variables in parent modules override variables in imports.



Imports may be made optional by putting a `?` after the `import` keyword:



```mf

import? 'foo/bar.just'

```



Missing source files for optional imports do not produce an error.



### Modules1.19.0



A `justfile` can declare modules using `mod` statements.



`mod` statements were stabilized in `just`1.31.0. In earlier

versions, you'll need to use the `--unstable` flag, `set unstable`, or set the

`JUST_UNSTABLE` environment variable to use them.



If you have the following `justfile`:



```mf

mod bar



a:

  @echo A

```



And the following text in `bar.just`:



```just

b:

  @echo B

```



`bar.just` will be included in `justfile` as a submodule. Recipes, aliases, and

variables defined in one submodule cannot be used in another, and each module

uses its own settings.



Recipes in submodules can be invoked as subcommands:



```console

$ just bar b

B

```



Or with path syntax:



```console

$ just bar::b

B

```



If a module is named `foo`, just will search for the module file in `foo.just`,

`foo/mod.just`, `foo/justfile`, and `foo/.justfile`. In the latter two cases,

the module file may have any capitalization.



Module statements may be of the form:



```mf

mod foo 'PATH'

```



Which loads the module's source file from `PATH`, instead of from the usual

locations. A leading `~/` in `PATH` is replaced with the current user's home

directory. `PATH` may point to the module source file itself, or to a directory

containing the module source file with the name `mod.just`, `justfile`, or

`.justfile`. In the latter two cases, the module file may have any

capitalization.



Environment files are only loaded for the root justfile, and loaded environment

variables are available in submodules. Settings in submodules that affect

environment file loading are ignored.



Recipes in submodules without the `[no-cd]` attribute run with the working

directory set to the directory containing the submodule source file.



`justfile()` and `justfile_directory()` always return the path to the root

justfile and the directory that contains it, even when called from submodule

recipes.



Modules may be made optional by putting a `?` after the `mod` keyword:



```mf

mod? foo

```



Missing source files for optional modules do not produce an error.



Optional modules with no source file do not conflict, so you can have multiple

mod statements with the same name, but with different source file paths, as

long as at most one source file exists:



```mf

mod? foo 'bar.just'

mod? foo 'baz.just'

```



Modules may be given doc comments which appear in `--list`

output1.30.0:



```mf

# foo is a great module!

mod foo

```



```console

$ just --list

Available recipes:

    foo ... # foo is a great module!

```



Modules are still missing a lot of features, for example, the ability to depend

on recipes and refer to variables in other modules. See the

[module improvement tracking issue](https://github.com/casey/just/issues/2252)

for more information.



### Hiding `justfile`s



`just` looks for `justfile`s named `justfile` and `.justfile`, which can be

used to keep a `justfile` hidden.



### Just Scripts



By adding a shebang line to the top of a `justfile` and making it executable,

`just` can be used as an interpreter for scripts:



```console

$ cat > script < formatted-justfile

```



The `--dump` command can be used with `--dump-format json` to print a JSON

representation of a `justfile`.



### Fallback to parent `justfile`s



If a recipe is not found in a `justfile` and the `fallback` setting is set,

`just` will look for `justfile`s in the parent directory and up, until it

reaches the root directory. `just` will stop after it reaches a `justfile` in

which the `fallback` setting is `false` or unset.



As an example, suppose the current directory contains this `justfile`:



```just

set fallback

foo:

  echo foo

```



And the parent directory contains this `justfile`:



```just

bar:

  echo bar

```



```console

$ just bar

Trying ../justfile

echo bar

bar

```



### Avoiding Argument Splitting



Given this `justfile`:



```just

foo argument:

  touch {{argument}}

```



The following command will create two files, `some` and `argument.txt`:



```console

$ just foo "some argument.txt"

```



The users shell will parse `"some argument.txt"` as a single argument, but when

`just` replaces `touch {{argument}}` with `touch some argument.txt`, the quotes

are not preserved, and `touch` will receive two arguments.



There are a few ways to avoid this: quoting, positional arguments, and exported

arguments.



#### Quoting



Quotes can be added around the `{{argument}}` interpolation:



```just

foo argument:

  touch '{{argument}}'

```



This preserves `just`'s ability to catch variable name typos before running,

for example if you were to write `{{argument}}`, but will not do what you want

if the value of `argument` contains single quotes.



#### Positional Arguments



The `positional-arguments` setting causes all arguments to be passed as

positional arguments, allowing them to be accessed with `$1`, `$2`, …, and

`$@`, which can be then double-quoted to avoid further splitting by the shell:



```just

set positional-arguments



foo argument:

  touch "$1"

```



This defeats `just`'s ability to catch typos, for example if you type `$2`

instead of `$1`, but works for all possible values of `argument`, including

those with double quotes.



#### Exported Arguments



All arguments are exported when the `export` setting is set:



```just

set export



foo argument:

  touch "$argument"

```



Or individual arguments may be exported by prefixing them with `$`:



```just

foo $argument:

  touch "$argument"

```



This defeats `just`'s ability to catch typos, for example if you type

`$argument`, but works for all possible values of `argument`, including those

with double quotes.



### Configuring the Shell



There are a number of ways to configure the shell for linewise recipes, which

are the default when a recipe does not start with a `#!` shebang. Their

precedence, from highest to lowest, is:



1. The `--shell` and `--shell-arg` command line options. Passing either of

   these will cause `just` to ignore any settings in the current justfile.

2. `set windows-shell := [...]`

3. `set windows-powershell` (deprecated)

4. `set shell := [...]`



Since `set windows-shell` has higher precedence than `set shell`, you can use

`set windows-shell` to pick a shell on Windows, and `set shell` to pick a shell

for all other platforms.



### Timestamps



`just` can print timestamps before each recipe commands:



```just

recipe:

  echo one

  sleep 2

  echo two

```



```

$ just --timestamp recipe

[07:28:46] echo one

one

[07:28:46] sleep 2

[07:28:48] echo two

two

```



By default, timestamps are formatted as `HH:MM:SS`. The format can be changed

with `--timestamp-format`:



```

$ just --timestamp recipe --timestamp-format '%H:%M:%S%.3f %Z'

[07:32:11:.349 UTC] echo one

one

[07:32:11:.350 UTC] sleep 2

[07:32:13:.352 UTC] echo two

two

```



The argument to `--timestamp-format` is a `strftime`-style format string, see

the

[`chrono` library docs](https://docs.rs/chrono/latest/chrono/format/strftime/index.html)

for details.



Changelog

---------



A changelog for the latest release is available in

[CHANGELOG.md](https://raw.githubusercontent.com/casey/just/master/CHANGELOG.md).

Changelogs for previous releases are available on

[the releases page](https://github.com/casey/just/releases). `just --changelog`

can also be used to make a `just` binary print its changelog.



Miscellanea

-----------



### Re-running recipes when files change



[`watchexec`](https://github.com/mattgreen/watchexec) can re-run any command

when files change.



To re-run the recipe `foo` when any file changes:



```console

watchexec just foo

```



See `watchexec --help` for more info, including how to specify which files

should be watched for changes.



### Running tasks in parallel



GNU parallel can be used to run tasks concurrently:



```just

parallel:

  #!/usr/bin/env -S parallel --shebang --ungroup --jobs {{ num_cpus() }}

  echo task 1 start; sleep 3; echo task 1 done

  echo task 2 start; sleep 3; echo task 2 done

  echo task 3 start; sleep 3; echo task 3 done

  echo task 4 start; sleep 3; echo task 4 done

```



### Shell Alias



For lightning-fast command running, put `alias j=just` in your shell's

configuration file.



In `bash`, the aliased command may not keep the shell completion functionality

described in the next section. Add the following line to your `.bashrc` to use

the same completion function as `just` for your aliased command:



```console

complete -F _just -o bashdefault -o default j

```



### Shell Completion Scripts



Shell completion scripts for Bash, Elvish, Fish, Nushell, PowerShell, and Zsh

are available [release archives](https://github.com/casey/just/releases).



The `just` binary can also generate the same completion scripts at runtime

using `just --completions SHELL`:



```console

$ just --completions zsh > just.zsh

```



Please refer to your shell's documentation for how to install them.



*macOS Note:* Recent versions of macOS use zsh as the default shell. If you use

Homebrew to install `just`, it will automatically install the most recent copy

of the zsh completion script in the Homebrew zsh directory, which the built-in

version of zsh doesn't know about by default. It's best to use this copy of the

script if possible, since it will be updated whenever you update `just` via

Homebrew. Also, many other Homebrew packages use the same location for

completion scripts, and the built-in zsh doesn't know about those either. To

take advantage of `just` completion in zsh in this scenario, you can set

`fpath` to the Homebrew location before calling `compinit`. Note also that Oh

My Zsh runs `compinit` by default. So your `.zshrc` file could look like this:



```zsh

# Init Homebrew, which adds environment variables

eval "$(brew shellenv)"



fpath=($HOMEBREW_PREFIX/share/zsh/site-functions $fpath)



# Then choose one of these options:

# 1. If you're using Oh My Zsh, you can initialize it here

# source $ZSH/oh-my-zsh.sh



# 2. Otherwise, run compinit yourself

# autoload -U compinit

# compinit

```



### Man Page



`just` can print its own man page with `just --man`. Man pages are written in

[`roff`](https://en.wikipedia.org/wiki/Roff_%28software%29), a venerable markup

language and one of the first practical applications of Unix. If you have

[`groff`](https://www.gnu.org/software/groff/) installed you can view the man

page with  `just --man | groff -mandoc -Tascii | less`.



### Grammar



A non-normative grammar of `justfile`s can be found in

[GRAMMAR.md](https://github.com/casey/just/blob/master/GRAMMAR.md).



### just.sh



Before `just` was a fancy Rust program it was a tiny shell script that called

`make`. You can find the old version in

[contrib/just.sh](https://github.com/casey/just/blob/master/contrib/just.sh).



### Global and User `justfile`s



If you want some recipes to be available everywhere, you have a few options.



#### Global Justfile



`just --global-justfile`, or `just -g` for short, searches the following paths,

in-order, for a justfile:



- `$XDG_CONFIG_HOME/just/justfile`

- `$HOME/.config/just/justfile`

- `$HOME/justfile`

- `$HOME/.justfile`



You can put recipes that are used across many projects in a global justfile to

easily invoke them from any directory.



#### User justfile tips



You can also adopt some of the following workflows. These tips assume you've

created a `justfile` at `~/.user.justfile`, but you can put this `justfile`

at any convenient path on your system.



##### Recipe Aliases



If you want to call the recipes in `~/.user.justfile` by name, and don't mind

creating an alias for every recipe, add the following to your shell's

initialization script:



```console

for recipe in `just --justfile ~/.user.justfile --summary`; do

  alias $recipe="just --justfile ~/.user.justfile --working-directory . $recipe"

done

```



Now, if you have a recipe called `foo` in `~/.user.justfile`, you can just type

`foo` at the command line to run it.



It took me way too long to realize that you could create recipe aliases like

this. Notwithstanding my tardiness, I am very pleased to bring you this major

advance in `justfile` technology.



##### Forwarding Alias



If you'd rather not create aliases for every recipe, you can create a single alias:



```console

alias .j='just --justfile ~/.user.justfile --working-directory .'

```



Now, if you have a recipe called `foo` in `~/.user.justfile`, you can just type

`.j foo` at the command line to run it.



I'm pretty sure that nobody actually uses this feature, but it's there.



¯\\\_(ツ)\_/¯



##### Customization



You can customize the above aliases with additional options. For example, if

you'd prefer to have the recipes in your `justfile` run in your home directory,

instead of the current directory:



```console

alias .j='just --justfile ~/.user.justfile --working-directory ~'

```



### Node.js `package.json` Script Compatibility



The following export statement gives `just` recipes access to local Node module

binaries, and makes `just` recipe commands behave more like `script` entries in

Node.js `package.json` files:



```just

export PATH := "./node_modules/.bin:" + env_var('PATH')

```



### Paths on Windows



On Windows, functions that return paths will return `\`-separated paths. When

not using PowerShell or `cmd.exe` these paths should be quoted to prevent the

`\`s from being interpreted as character escapes:



```just

ls:

    echo '{{absolute_path(".")}}'

```



### Remote Justfiles



If you wish to include a `mod` or `import` source file in many `justfiles`

without needing to duplicate it, you can use an optional `mod` or `import`,

along with a recipe to fetch the module source:



```just

import? 'foo.just'



fetch:

  curl https://raw.githubusercontent.com/casey/just/master/justfile > foo.just

```



Given the above `justfile`, after running `just fetch`, the recipes in

`foo.just` will be available.



### Alternatives and Prior Art



There is no shortage of command runners! Some more or less similar alternatives

to `just` include:



- [make](https://en.wikipedia.org/wiki/Make_(software)): The Unix build tool

  that inspired `just`. There are a few different modern day descendents of the

  original `make`, including

  [FreeBSD Make](https://www.freebsd.org/cgi/man.cgi?make(1)) and

  [GNU Make](https://www.gnu.org/software/make/).

- [task](https://github.com/go-task/task): A YAML-based command runner written

  in Go.

- [maid](https://github.com/egoist/maid): A Markdown-based command runner

  written in JavaScript.

- [microsoft/just](https://github.com/microsoft/just): A JavaScript-based

  command runner written in JavaScript.

- [cargo-make](https://github.com/sagiegurari/cargo-make): A command runner for

  Rust projects.

- [mmake](https://github.com/tj/mmake): A wrapper around `make` with a number

  of improvements, including remote includes.

- [robo](https://github.com/tj/robo): A YAML-based command runner written in

  Go.

- [mask](https://github.com/jakedeichert/mask): A Markdown-based command runner

  written in Rust.

- [makesure](https://github.com/xonixx/makesure): A simple and portable command

  runner written in AWK and shell.

- [haku](https://github.com/VladimirMarkelov/haku): A make-like command runner

  written in Rust.



Contributing

------------



`just` welcomes your contributions! `just` is released under the maximally

permissive

[CC0](https://creativecommons.org/publicdomain/zero/1.0/legalcode.txt) public

domain dedication and fallback license, so your changes must also be released

under this license.



### Getting Started



`just` is written in Rust. Use

[rustup](https://www.rust-lang.org/tools/install) to install a Rust toolchain.



`just` is extensively tested. All new features must be covered by unit or

integration tests. Unit tests are under

[src](https://github.com/casey/just/blob/master/src), live alongside the code

being tested, and test code in isolation. Integration tests are in the [tests

directory](https://github.com/casey/just/blob/master/tests) and test the `just`

binary from the outside by invoking `just` on a given `justfile` and set of

command-line arguments, and checking the output.



You should write whichever type of tests are easiest to write for your feature

while still providing good test coverage.



Unit tests are useful for testing new Rust functions that are used internally

and as an aid for development. A good example are the unit tests which cover

the

[`unindent()` function](https://github.com/casey/just/blob/master/src/unindent.rs),

used to unindent triple-quoted strings and backticks. `unindent()` has a bunch

of tricky edge cases which are easy to exercise with unit tests that call

`unindent()` directly.



Integration tests are useful for making sure that the final behavior of the

`just` binary is correct. `unindent()` is also covered by integration tests

which make sure that evaluating a triple-quoted string produces the correct

unindented value. However, there are not integration tests for all possible

cases. These are covered by faster, more concise unit tests that call

`unindent()` directly.



Existing integration tests are in two forms, those that use the `test!` macro

and those that use the `Test` struct directly. The `test!` macro, while often

concise, is less flexible and harder to understand, so new tests should use the

`Test` struct. The `Test` struct is a builder which allows for easily invoking

`just` with a given `justfile`, arguments, and environment variables, and

checking the program's stdout, stderr, and exit code .



### Contribution Workflow



1. Make sure the feature is wanted. There should be an open issue about the

   feature with a comment from [@casey](https://github.com/casey) saying that

   it's a good idea or seems reasonable. If there isn't, open a new issue and

   ask for feedback.



   There are lots of good features which can't be merged, either because they

   aren't backwards compatible, have an implementation which would

   overcomplicate the codebase, or go against `just`'s design philosophy.



2. Settle on the design of the feature. If the feature has multiple possible

   implementations or syntaxes, make sure to nail down the details in the

   issue.



3. Clone `just` and start hacking. The best workflow is to have the code you're

   working on in an editor alongside a job that re-runs tests whenever a file

   changes. You can run such a job by installing

   [cargo-watch](https://github.com/watchexec/cargo-watch) with `cargo install

   cargo-watch` and running `just watch test`.



4. Add a failing test for your feature. Most of the time this will be an

   integration test which exercises the feature end-to-end. Look for an

   appropriate file to put the test in in

   [tests](https://github.com/casey/just/blob/master/tests), or add a new file

   in [tests](https://github.com/casey/just/blob/master/tests) and add a `mod`

   statement importing that file in

   [tests/lib.rs](https://github.com/casey/just/blob/master/tests/lib.rs).



5. Implement the feature.



6. Run `just ci` to make sure that all tests, lints, and checks pass.



7. Open a PR with the new code that is editable by maintainers. PRs often

   require rebasing and minor tweaks. If the PR is not editable by maintainers,

   each rebase and tweak will require a round trip of code review. Your PR may

   be summarily closed if it is not editable by maintainers.



8. Incorporate feedback.



9. Enjoy the sweet feeling of your PR getting merged!



Feel free to open a draft PR at any time for discussion and feedback.



### Hints



Here are some hints to get you started with specific kinds of new features,

which you can use in addition to the contribution workflow above.



#### Adding a New Attribute



1. Write a new integration test in

   [tests/attributes.rs](https://github.com/casey/just/blob/master/tests/attributes.rs).



2. Add a new variant to the

   [`Attribute`](https://github.com/casey/just/blob/master/src/attribute.rs)

   enum.



3. Implement the functionality of the new attribute.



4. Run `just ci` to make sure that all tests pass.



### Janus



[Janus](https://github.com/casey/janus) is a tool for checking whether a change

to `just` breaks or changes the interpretation of existing `justfile`s. It

collects and analyzes public `justfile`s on GitHub.



Before merging a particularly large or gruesome change, Janus should be run to

make sure that nothing breaks. Don't worry about running Janus yourself, Casey

will happily run it for you on changes that need it.



### Minimum Supported Rust Version



The minimum supported Rust version, or MSRV, is current stable Rust. It may

build on older versions of Rust, but this is not guaranteed.



### New Releases



New releases of `just` are made frequently so that users quickly get access to

new features.



Release commit messages use the following template:



```

Release x.y.z



- Bump version: x.y.z → x.y.z

- Update changelog

- Update changelog contributor credits

- Update dependencies

- Update version references in readme

```



Frequently Asked Questions

--------------------------



### What are the idiosyncrasies of Make that Just avoids?



`make` has some behaviors which are confusing, complicated, or make it

unsuitable for use as a general command runner.



One example is that under some circumstances, `make` won't actually run the

commands in a recipe. For example, if you have a file called `test` and the

following makefile:



```just

test:

  ./test

```



`make` will refuse to run your tests:



```console

$ make test

make: `test' is up to date.

```



`make` assumes that the `test` recipe produces a file called `test`. Since this

file exists and the recipe has no other dependencies, `make` thinks that it

doesn't have anything to do and exits.



To be fair, this behavior is desirable when using `make` as a build system, but

not when using it as a command runner. You can disable this behavior for

specific targets using `make`'s built-in

[`.PHONY` target name](https://www.gnu.org/software/make/manual/html_node/Phony-Targets.html),

but the syntax is verbose and can be hard to remember. The explicit list of

phony targets, written separately from the recipe definitions, also introduces

the risk of accidentally defining a new non-phony target. In `just`, all

recipes are treated as if they were phony.



Other examples of `make`'s idiosyncrasies include the difference between `=`

and `:=` in assignments, the confusing error messages that are produced if you

mess up your makefile, needing `$$` to use environment variables in recipes,

and incompatibilities between different flavors of `make`.



### What's the relationship between Just and Cargo build scripts?



[`cargo` build scripts](http://doc.crates.io/build-script.html) have a pretty

specific use, which is to control how `cargo` builds your Rust project. This

might include adding flags to `rustc` invocations, building an external

dependency, or running some kind of codegen step.



`just`, on the other hand, is for all the other miscellaneous commands you

might run as part of development. Things like running tests in different

configurations, linting your code, pushing build artifacts to a server,

removing temporary files, and the like.



Also, although `just` is written in Rust, it can be used regardless of the

language or build system your project uses.



Further Ramblings

-----------------



I personally find it very useful to write a `justfile` for almost every

project, big or small.



On a big project with multiple contributors, it's very useful to have a file

with all the commands needed to work on the project close at hand.



There are probably different commands to test, build, lint, deploy, and the

like, and having them all in one place is useful and cuts down on the time you

have to spend telling people which commands to run and how to type them.



And, with an easy place to put commands, it's likely that you'll come up with

other useful things which are part of the project's collective wisdom, but

which aren't written down anywhere, like the arcane commands needed for some

part of your revision control workflow, to install all your project's

dependencies, or all the random flags you might need to pass to the build

system.



Some ideas for recipes:



- Deploying/publishing the project



- Building in release mode vs debug mode



- Running in debug mode or with logging enabled



- Complex git workflows



- Updating dependencies



- Running different sets of tests, for example fast tests vs slow tests, or

  running them with verbose output



- Any complex set of commands that you really should write down somewhere, if

  only to be able to remember them



Even for small, personal projects it's nice to be able to remember commands by

name instead of ^Reverse searching your shell history, and it's a huge boon to

be able to go into an old project written in a random language with a

mysterious build system and know that all the commands you need to do whatever

you need to do are in the `justfile`, and that if you type `just` something

useful (or at least interesting!) will probably happen.



For ideas for recipes, check out

[this project's `justfile`](https://github.com/casey/just/blob/master/justfile),

or some of the

`justfile`s

[out in the wild](https://github.com/search?q=path%3A**%2Fjustfile&type=code).



Anyways, I think that's about it for this incredibly long-winded README.



I hope you enjoy using `just` and find great success and satisfaction in all

your computational endeavors!



😸