Awesome
<div align=right>Table of Contents↗️</div> <h1 align=center><code>just</code></h1> <div align=center> <a href=https://crates.io/crates/just> <img src=https://img.shields.io/crates/v/just.svg alt="crates.io version"> </a> <a href=https://github.com/casey/just/actions> <img src=https://github.com/casey/just/actions/workflows/ci.yaml/badge.svg alt="build status"> </a> <a href=https://github.com/casey/just/releases> <img src=https://img.shields.io/github/downloads/casey/just/total.svg alt=downloads> </a> <a href=https://discord.gg/ezYScXR> <img src=https://img.shields.io/discord/695580069837406228?logo=discord alt="chat on discord"> </a> <a href=mailto:casey@rodarmor.com?subject=Thanks%20for%20Just!> <img src=https://img.shields.io/badge/Say%20Thanks-!-1EAEDB.svg alt="say thanks"> </a> </div> <br>just
is a handy way to save and run project-specific commands.
This readme is also available as a book.
(中文文档在 这里, 快看过来!)
Commands, called recipes, are stored in a file called justfile
with syntax
inspired by make
:
You can then run them with just RECIPE
:
$ 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 ofmake
's complexity and idiosyncrasies. 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.) -
Errors are specific and informative, and syntax errors are reported along with their source context.
-
Recipes can accept command line arguments.
-
Wherever possible, errors are resolved statically. Unknown recipes and circular dependencies are reported before anything runs.
-
just
loads.env
files, making it easy to populate environment variables. -
Recipes can be listed from the command line.
-
Command line completion scripts are available for most popular shells.
-
Recipes can be written in arbitrary languages, like Python or NodeJS.
-
just
can be invoked from any subdirectory, not just the directory that contains thejustfile
. -
And much more!
If you need help with just
please feel free to open an issue or ping me on
Discord. 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,
GitHub Desktop, or
Cygwin.
If you'd rather not install sh
, you can use the shell
setting to use the
shell of your choice.
Like PowerShell:
# use PowerShell instead of sh:
set shell := ["powershell.exe", "-c"]
hello:
Write-Host "Hello, world!"
…or cmd.exe
:
# 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
<table> <thead> <tr> <th>Operating System</th> <th>Package Manager</th> <th>Package</th> <th>Command</th> </tr> </thead> <tbody> <tr> <td><a href=https://alpinelinux.org>Alpine Linux</a></td> <td><a href=https://wiki.alpinelinux.org/wiki/Alpine_Linux_package_management>apk-tools</a></td> <td><a href=https://pkgs.alpinelinux.org/package/edge/community/x86_64/just>just</a></td> <td><code>apk add just</code></td> </tr> <tr> <td><a href=https://www.archlinux.org>Arch Linux</a></td> <td><a href=https://wiki.archlinux.org/title/Pacman>pacman</a></td> <td><a href=https://archlinux.org/packages/extra/x86_64/just/>just</a></td> <td><code>pacman -S just</code></td> </tr> <tr> <td> <a href=https://debian.org>Debian 13 (unreleased)</a> and <a href=https://ubuntu.com>Ubuntu 24.04</a> derivatives</td> <td><a href=https://en.wikipedia.org/wiki/APT_(software)>apt</a></td> <td><a href=https://packages.debian.org/trixie/just>just</a></td> <td><code>apt install just</code></td> </tr> <tr> <td><a href=https://debian.org>Debian</a> and <a href=https://ubuntu.com>Ubuntu</a> derivatives</td> <td><a href=https://mpr.makedeb.org>MPR</a></td> <td><a href=https://mpr.makedeb.org/packages/just>just</a></td> <td> <code>git clone https://mpr.makedeb.org/just</code><br> <code>cd just</code><br> <code>makedeb -si</code> </td> </tr> <tr> <td><a href=https://debian.org>Debian</a> and <a href=https://ubuntu.com>Ubuntu</a> derivatives</td> <td><a href=https://docs.makedeb.org/prebuilt-mpr>Prebuilt-MPR</a></td> <td><a href=https://mpr.makedeb.org/packages/just>just</a></td> <td> <sup><b>You must have the <a href=https://docs.makedeb.org/prebuilt-mpr/getting-started/#setting-up-the-repository>Prebuilt-MPR set up</a> on your system in order to run this command.</b></sup><br> <code>apt install just</code> </td> </tr> <tr> <td><a href=https://getfedora.org>Fedora Linux</a></td> <td><a href=https://dnf.readthedocs.io/en/latest/>DNF</a></td> <td><a href=https://src.fedoraproject.org/rpms/rust-just>just</a></td> <td><code>dnf install just</code></td> </tr> <tr> <td><a href=https://www.freebsd.org>FreeBSD</a></td> <td><a href=https://www.freebsd.org/doc/handbook/pkgng-intro.html>pkg</a></td> <td><a href=https://www.freshports.org/deskutils/just/>just</a></td> <td><code>pkg install just</code></td> </tr> <tr> <td><a href=https://www.gentoo.org>Gentoo Linux</a></td> <td><a href=https://wiki.gentoo.org/wiki/Portage>Portage</a></td> <td><a href=https://github.com/gentoo-mirror/guru/tree/master/dev-build/just>guru/dev-build/just</a></td> <td> <code>eselect repository enable guru</code><br> <code>emerge --sync guru</code><br> <code>emerge dev-build/just</code> </td> </tr> <tr> <td><a href=https://en.wikipedia.org/wiki/MacOS>macOS</a></td> <td><a href=https://www.macports.org>MacPorts</a></td> <td><a href=https://ports.macports.org/port/just/summary>just</a></td> <td><code>port install just</code></td> </tr> <tr> <td><a href=https://en.wikipedia.org/wiki/Microsoft_Windows>Microsoft Windows</a></td> <td><a href=https://chocolatey.org>Chocolatey</a></td> <td><a href=https://github.com/michidk/just-choco>just</a></td> <td><code>choco install just</code></td> </tr> <tr> <td><a href=https://en.wikipedia.org/wiki/Microsoft_Windows>Microsoft Windows</a></td> <td><a href=https://scoop.sh>Scoop</a></td> <td><a href=https://github.com/ScoopInstaller/Main/blob/master/bucket/just.json>just</a></td> <td><code>scoop install just</code></td> </tr> <tr> <td><a href=https://en.wikipedia.org/wiki/Microsoft_Windows>Microsoft Windows</a></td> <td><a href=https://learn.microsoft.com/en-us/windows/package-manager/>Windows Package Manager</a></td> <td><a href=https://github.com/microsoft/winget-pkgs/tree/master/manifests/c/Casey/Just>Casey/Just</a></td> <td><code>winget install --id Casey.Just --exact</code></td> </tr> <tr> <td><a href=https://nixos.org/nixos/>NixOS</a></td> <td><a href=https://nixos.org/nix/>Nix</a></td> <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix>just</a></td> <td><code>nix-env -iA nixos.just</code></td> </tr> <tr> <td><a href=https://opensuse.org>openSUSE</a></td> <td><a href=https://en.opensuse.org/Portal:Zypper>Zypper</a></td> <td><a href=https://build.opensuse.org/package/show/Base:System/just>just</a></td> <td><code>zypper in just</code></td> </tr> <tr> <td><a href=https://getsol.us>Solus</a></td> <td><a href=https://getsol.us/articles/package-management/basics/en>eopkg</a></td> <td><a href=https://dev.getsol.us/source/just/>just</a></td> <td><code>eopkg install just</code></td> </tr> <tr> <td><a href=https://github.com/casey/just/releases>Various</a></td> <td><a href=https://asdf-vm.com>asdf</a></td> <td><a href=https://github.com/olofvndrhr/asdf-just>just</a></td> <td> <code>asdf plugin add just</code><br> <code>asdf install just <version></code> </td> </tr> <tr> <td><a href=https://forge.rust-lang.org/release/platform-support.html>Various</a></td> <td><a href=https://www.rust-lang.org>Cargo</a></td> <td><a href=https://crates.io/crates/just>just</a></td> <td><code>cargo install just</code></td> </tr> <tr> <td><a href=https://docs.conda.io/en/latest/miniconda.html#system-requirements>Various</a></td> <td><a href=https://docs.conda.io/projects/conda/en/latest/index.html>Conda</a></td> <td><a href=https://anaconda.org/conda-forge/just>just</a></td> <td><code>conda install -c conda-forge just</code></td> </tr> <tr> <td><a href=https://docs.brew.sh/Installation>Various</a></td> <td><a href=https://brew.sh>Homebrew</a></td> <td><a href=https://formulae.brew.sh/formula/just>just</a></td> <td><code>brew install just</code></td> </tr> <tr> <td><a href=https://nixos.org/download.html#download-nix>Various</a></td> <td><a href=https://nixos.org/nix/>Nix</a></td> <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix>just</a></td> <td><code>nix-env -iA nixpkgs.just</code></td> </tr> <tr> <td><a href=https://voidlinux.org>Void Linux</a></td> <td><a href=https://wiki.voidlinux.org/XBPS>XBPS</a></td> <td><a href=https://github.com/void-linux/void-packages/blob/master/srcpkgs/just/template>just</a></td> <td><code>xbps-install -S just</code></td> </tr> </tbody> </table>Pre-Built Binaries
Pre-built binaries for Linux, MacOS, and Windows can be found on the releases page.
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
:
curl --proto '=https' --tlsv1.2 -sSf https://just.systems/install.sh | bash -s -- --to DEST
For example, to install just
to ~/bin
:
# 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
.
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:
- uses: extractions/setup-just@v1
with:
just-version: 1.5.0 # optional semver specification, otherwise latest
Or with taiki-e/install-action:
- uses: taiki-e/install-action@just
Release RSS Feed
An RSS feed of just
releases is available here.
Node.js Installation
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.
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 plugin provides syntax
highlighting for justfile
s.
Install it with your favorite package manager, like Plug:
call plug#begin()
Plug 'NoahTheDuke/vim-just'
call plug#end()
Or with Vim's built-in package support:
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 is an 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
:
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:
# vim: set ft=make :
Emacs
just-mode provides syntax
highlighting and automatic indentation of justfile
s. It is available on
MELPA as just-mode.
justl 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:
# Local Variables:
# mode: makefile
# End:
Visual Studio Code
An extension for VS Code is available here.
Unmaintained VS Code extensions include skellock/vscode-just and sclu1034/vscode-just.
JetBrains IDEs
A plugin for JetBrains IDEs by linux_china is available here.
Kakoune
Kakoune supports justfile
syntax highlighting out of the box, thanks to
TeddyDD.
Helix
Helix supports justfile
syntax highlighting
out-of-the-box since version 23.05.
Sublime Text
The Just package by
nk9 with just
syntax and some other tools is
available on PackageControl.
Micro
Micro supports Justfile syntax highlighting out of the box, thanks to 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 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.
Once just
is installed and working, create a file named justfile
in the
root of your project with the following contents:
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
:
$ just
echo 'This is a recipe!'
This is a recipe!
One or more arguments specify the recipe(s) to run:
$ 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:
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
:
build:
cc main.c foo.c bar.c -o main
test: build
./test
sloc:
@echo "`wc -l *.c` lines of code"
$ 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:
$ 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:
$ 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 and on
GitHub.
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:
test:
cargo test
You can also use dependencies to run multiple recipes by default:
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:
default:
just --list
Listing Available Recipes
Recipes can be listed in alphabetical order with just --list
:
$ just --list
Available recipes:
build
test
deploy
lint
Recipes in submodules 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:
$ just --summary
build test deploy lint
Pass --unsorted
to print recipes in the order they appear in the justfile
:
test:
echo 'Testing!'
build:
echo 'Building!'
$ just --list --unsorted
Available recipes:
test
build
$ 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:
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
:
$ just --list --list-heading $'Cool stuff…\n'
Cool stuff…
test
build
And the indentation can be customized with --list-prefix
:
$ 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:
$ just --list --list-heading ''
test
build
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.
@foo:
pwd
[no-cd]
@bar:
pwd
$ 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.
set working-directory := 'bar'
@foo:
pwd
$ pwd
/home/bob
$ just foo
/home/bob/bar
Aliases
Aliases allow recipes to be invoked on the command line with alternative names:
alias b := build
build:
echo 'Building!'
$ 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:
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 <sup>1.33.0</sup> | [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 <sup>1.31.0</sup> | 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 <sup>1.33.0</sup> | string | - | Set the working directory for recipes and backticks, relative to the default working directory. |
Boolean settings can be written as:
set NAME
Which is equivalent to:
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
.
set allow-duplicate-recipes
@foo:
echo foo
@foo:
echo bar
$ 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
.
set allow-duplicate-variables
a := "foo"
a := "bar"
@foo:
echo $a
$ 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.
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:
# a comment, will be ignored
DATABASE_ADDRESS=localhost:6379
SERVER_PORT=1337
And your justfile
contains:
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:
$ 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
.
set export
a := "hello"
@foo b:
echo $a
echo $b
$ 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:
set positional-arguments
@foo bar:
echo $0
echo $1
Will produce the following output:
$ 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 $@
expand to nothing
(i.e., they are removed).
This example recipe will print arguments one by one on separate lines:
set positional-arguments
@test *args='':
bash -c 'while (( "$#" )); do echo - $1; shift; done' -- "$@"
Running it with two arguments:
$ just test foo "bar baz"
- foo
- bar baz
Positional arguments may also be turned on on a per-recipe basis with the
[positional-arguments]
attribute<sup>1.29.0</sup>:
[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.
Shell
The shell
setting controls the command used to invoke recipe lines and
backticks. Shebang recipes are unaffected. The default shell is sh -cu
.
# 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
:
set windows-shell := ["powershell.exe", "-NoLogo", "-Command"]
hello:
Write-Host "Hello, world!"
See 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.
set windows-powershell := true
hello:
Write-Host "Hello, world!"
Python 3
set shell := ["python3", "-c"]
Bash
set shell := ["bash", "-uc"]
Z Shell
set shell := ["zsh", "-uc"]
Fish
set shell := ["fish", "-c"]
Nushell
set shell := ["nu", "-c"]
If you want to change the default table mode to light
:
set shell := ['nu', '-m', 'light', '-c']
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
:
# build stuff
build:
./bin/build
# test stuff
test:
./bin/test
$ 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:
# This comment won't appear
[doc('Build stuff')]
build:
./bin/build
# This one won't either
[doc]
test:
./bin/test
$ just --list
Available recipes:
build # Build stuff
test
Variables and Substitution
Variables, strings, concatenation, path joining, and substitution using {{…}}
are supported:
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}} me@server.com:release/
rm -rf {{tarball}} {{tardir}}
Joining Paths
The /
operator can be used to join two strings with a slash:
foo := "a" / "b"
$ just --evaluate foo
a/b
Note that a /
is added even if one is already present:
foo := "a/"
bar := foo / "b"
$ just --evaluate bar
a//b
Absolute paths can also be constructed<sup>1.5.0</sup>:
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 {{{{
:
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:
braces:
echo '{{'I {{LOVE}} curly braces!'}}'
Yet another option is to use {{ "{{" }}
:
braces:
echo 'I {{ "{{" }}LOVE}} curly braces!'
Strings
Double-quoted strings support escape sequences:
string-with-tab := "\t"
string-with-newline := "\n"
string-with-carriage-return := "\r"
string-with-double-quote := "\""
string-with-slash := "\\"
string-with-no-newline := "\
"
$ just --evaluate
"tring-with-carriage-return := "
string-with-double-quote := """
string-with-newline := "
"
string-with-no-newline := ""
string-with-slash := "\"
string-with-tab := " "
Strings may contain line breaks:
single := '
hello
'
double := "
goodbye
"
Single-quoted strings do not recognize escape sequences:
escapes := '\t\n\r\"\\'
$ 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:
# 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 expanded<sup>1.27.0</sup>:
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
-
:
foo:
-cat foo
echo 'Done!'
$ 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()
<sup>1.15.0</sup> - 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:
system-info:
@echo "This is an {{arch()}} machine".
$ 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
file.
External Commands
-
shell(command, args...)
<sup>1.27.0</sup> returns the standard output of shell scriptcommand
with zero or more positional argumentsargs
. The shell used to interpretcommand
is the same shell that is used to evaluate recipe lines, and can be changed withset shell := […]
.command
is passed as the first argument, so if the command is'echo $@'
, the full command line, with the default shell commandshell -cu
andargs
'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.
# 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')
# 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 namekey
, aborting if it is not present.
home_dir := env_var('HOME')
test:
echo "{{home_dir}}"
$ just
/home/user1
env_var_or_default(key, default)
— Retrieves the environment variable with namekey
, returningdefault
if it is not present.env(key)
<sup>1.15.0</sup> — Alias forenv_var(key)
.env(key, default)
<sup>1.15.0</sup> — Alias forenv_var_or_default(key, default)
.
Invocation Information
is_dependency()
- Returns the stringtrue
if the current recipe is being run as a dependency of another recipe, rather than being run directly, otherwise returns the stringfalse
.
Invocation Directory
invocation_directory()
- Retrieves the absolute path to the current directory whenjust
was invoked, beforejust
changed it (chdir'd) prior to executing commands. On Windows,invocation_directory()
usescygpath
to convert the invocation directory to a Cygwin-compatible/
-separated path. Useinvocation_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:
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.):
build:
cd {{invocation_directory()}}; ./some_script_that_needs_to_be_run_from_here
invocation_directory_native()
- Retrieves the absolute path to the current directory whenjust
was invoked, beforejust
changed it (chdir'd) prior to executing commands.
Justfile and Justfile Directory
-
justfile()
- Retrieves the path of the currentjustfile
. -
justfile_directory()
- Retrieves the path of the parent directory of the currentjustfile
.
For example, to run a command relative to the location of the current
justfile
:
script:
{{justfile_directory()}}/scripts/some_script
Source and Source Directory
-
source_file()
<sup>1.27.0</sup> - Retrieves the path of the current source file. -
source_directory()
<sup>1.27.0</sup> - 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 thejust
executable.
For example:
executable:
@echo The executable is at: {{just_executable()}}
$ just
The executable is at: /bin/just
Just Process ID
just_pid()
- Process ID of thejust
executable.
For example:
pid:
@echo The process ID is: {{ just_pid() }}
$ just
The process ID is: 420
String Manipulation
append(suffix, s)
<sup>1.27.0</sup> Appendsuffix
to whitespace-separated strings ins
.append('/src', 'foo bar baz')
→'foo/src bar/src baz/src'
prepend(prefix, s)
<sup>1.27.0</sup> Prependprefix
to whitespace-separated strings ins
.prepend('src/', 'foo bar baz')
→'src/foo src/bar src/baz'
encode_uri_component(s)
<sup>1.27.0</sup> - Percent-encode characters ins
except[A-Za-z0-9_.!~*'()-]
, matching the behavior of the JavaScriptencodeURIComponent
function.quote(s)
- Replace all single quotes with'\''
and prepend and append single quotes tos
. This is sufficient to escape special characters for many shells, including most Bourne shell descendants.replace(s, from, to)
- Replace all occurrences offrom
ins
toto
.replace_regex(s, regex, replacement)
- Replace all occurrences ofregex
ins
toreplacement
. Regular expressions are provided by the Rustregex
crate. See the syntax documentation for usage examples. Capture groups are supported. Thereplacement
string uses Replacement string syntax.trim(s)
- Remove leading and trailing whitespace froms
.trim_end(s)
- Remove trailing whitespace froms
.trim_end_match(s, pat)
- Remove suffix ofs
matchingpat
.trim_end_matches(s, pat)
- Repeatedly remove suffixes ofs
matchingpat
.trim_start(s)
- Remove leading whitespace froms
.trim_start_match(s, pat)
- Remove prefix ofs
matchingpat
.trim_start_matches(s, pat)
- Repeatedly remove prefixes ofs
matchingpat
.
Case Conversion
capitalize(s)
<sup>1.7.0</sup> - Convert first character ofs
to uppercase and the rest to lowercase.kebabcase(s)
<sup>1.7.0</sup> - Converts
tokebab-case
.lowercamelcase(s)
<sup>1.7.0</sup> - Converts
tolowerCamelCase
.lowercase(s)
- Converts
to lowercase.shoutykebabcase(s)
<sup>1.7.0</sup> - Converts
toSHOUTY-KEBAB-CASE
.shoutysnakecase(s)
<sup>1.7.0</sup> - Converts
toSHOUTY_SNAKE_CASE
.snakecase(s)
<sup>1.7.0</sup> - Converts
tosnake_case
.titlecase(s)
<sup>1.7.0</sup> - Converts
toTitle Case
.uppercamelcase(s)
<sup>1.7.0</sup> - Converts
toUpperCamelCase
.uppercase(s)
- Converts
to uppercase.
Path Manipulation
Fallible
absolute_path(path)
- Absolute path to relativepath
in the working directory.absolute_path("./bar.txt")
in directory/foo
is/foo/bar.txt
.canonicalize(path)
<sup>1.24.0</sup> - Canonicalizepath
by resolving symlinks and removing.
,..
, and extra/
s where possible.extension(path)
- Extension ofpath
.extension("/foo/bar.txt")
istxt
.file_name(path)
- File name ofpath
with any leading directory components removed.file_name("/foo/bar.txt")
isbar.txt
.file_stem(path)
- File name ofpath
without extension.file_stem("/foo/bar.txt")
isbar
.parent_directory(path)
- Parent directory ofpath
.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)
- Simplifypath
by removing extra path separators, intermediate.
components, and..
where possible.clean("foo//bar")
isfoo/bar
,clean("foo/..")
is.
,clean("foo/./bar")
isfoo/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 patha
with pathb
.join("foo/bar", "baz")
isfoo/bar/baz
. Accepts two or more arguments.
Filesystem Access
path_exists(path)
- Returnstrue
if the path points at an existing entity andfalse
otherwise. Traverses symbolic links, and returnsfalse
if the path is inaccessible or points to a broken symlink.
Error Reporting
error(message)
- Abort execution and report errormessage
to user.
UUID and Hash Generation
blake3(string)
<sup>1.25.0</sup> - Return BLAKE3 hash ofstring
as hexadecimal string.blake3_file(path)
<sup>1.25.0</sup> - Return BLAKE3 hash of file atpath
as hexadecimal string.sha256(string)
- Return the SHA-256 hash ofstring
as hexadecimal string.sha256_file(path)
- Return SHA-256 hash of file atpath
as hexadecimal string.uuid()
- Generate a random version 4 UUID.
Random
choose(n, alphabet)
<sup>1.27.0</sup> - Generate a string ofn
randomly selected characters fromalphabet
, which may not contain repeated characters. For example,choose('64', HEX)
will generate a random 64-character lowercase hex string.
Datetime
datetime(format)
<sup>1.30.0</sup> - Return local time withformat
.datetime_utc(format)
<sup>1.30.0</sup> - Return UTC time withformat
.
The arguments to datetime
and datetime_utc
are strftime
-style format
strings, see the
chrono
library docs
for details.
Semantic Versions
semver_matches(version, requirement)
<sup>1.16.0</sup> - Check whether a semanticversion
, e.g.,"0.1.0"
matches arequirement
, e.g.,">=0.1.0"
, returning"true"
if so and"false"
otherwise.
XDG Directories<sup>1.23.0</sup>
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,
and are implemented with the
dirs
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 <sup>1.27.0</sup> | "0123456789abcdef" |
HEXLOWER <sup>1.27.0</sup> | "0123456789abcdef" |
HEXUPPER <sup>1.27.0</sup> | "0123456789ABCDEF" |
@foo:
echo {{HEX}}
$ just foo
0123456789abcdef
Attributes
Recipes, mod
statements, and aliases may be annotated with attributes that change their behavior.
Name | Type | Description |
---|---|---|
[confirm] <sup>1.17.0</sup> | recipe | Require confirmation prior to executing recipe. |
[confirm('PROMPT')] <sup>1.23.0</sup> | recipe | Require confirmation prior to executing recipe with a custom prompt. |
[doc('DOC')] <sup>1.27.0</sup> | module, recipe | Set recipe or module's documentation comment to DOC . |
[extension('EXT')] <sup>1.32.0</sup> | recipe | Set shebang recipe script's file extension to EXT . EXT should include a period if one is desired. |
[group('NAME')] <sup>1.27.0</sup> | module, recipe | Put recipe or module in in group NAME . |
[linux] <sup>1.8.0</sup> | recipe | Enable recipe on Linux. |
[macos] <sup>1.8.0</sup> | recipe | Enable recipe on MacOS. |
[no-cd] <sup>1.9.0</sup> | recipe | Don't change directory before executing recipe. |
[no-exit-message] <sup>1.7.0</sup> | recipe | Don't print an error message if recipe fails. |
[no-quiet] <sup>1.23.0</sup> | recipe | Override globally quiet recipes and always echo out the recipe. |
[positional-arguments] <sup>1.29.0</sup> | recipe | Turn on positional arguments for this recipe. |
[private] <sup>1.10.0</sup> | alias, recipe | Make recipe, alias, or variable private. See Private Recipes. |
[script] <sup>1.33.0</sup> | recipe | Execute recipe as script. See script recipes for more details. |
[script(COMMAND)] <sup>1.32.0</sup> | recipe | Execute recipe as a script interpreted by COMMAND . See script recipes for more details. |
[unix] <sup>1.8.0</sup> | recipe | Enable recipe on Unixes. (Includes MacOS). |
[windows] <sup>1.8.0</sup> | recipe | Enable recipe on Windows. |
A recipe can have multiple attributes, either on multiple lines:
[no-cd]
[private]
foo:
echo "foo"
Or separated by commas on a single line<sup>1.14.0</sup>:
[no-cd, private]
foo:
echo "foo"
Enabling and Disabling Recipes<sup>1.8.0</sup>
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:
[unix]
run:
cc main.c
./a.out
[windows]
run:
cl main.c
main.exe
Disabling Changing Directory<sup>1.9.0</sup>
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:
[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 Recipes<sup>1.17.0</sup>
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.
[confirm]
delete-all:
rm -rf *
Custom Confirmation Prompt<sup>1.23.0</sup>
The default confirmation prompt can be overridden with [confirm(PROMPT)]
:
[confirm("Are you sure you want to delete everything?")]
delete-everything:
rm -rf *
Groups
Recipes and modules may be annotated with a group name:
[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:
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:
# 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 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:
foo := if "2" == "2" { "Good!" } else { "1984" }
bar:
@echo "{{foo}}"
$ just bar
Good!
It is also possible to test for inequality:
foo := if "hello" != "goodbye" { "xyz" } else { "abc" }
bar:
@echo {{foo}}
$ just bar
xyz
And match against regular expressions:
foo := if "hello" =~ 'hel+o' { "match" } else { "mismatch" }
bar:
@echo {{foo}}
$ just bar
match
Regular expressions are provided by the regex crate, whose syntax is documented on docs.rs. 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.
foo := if env_var("RELEASE") == "true" { `get-something-from-release-database` } else { "dummy-value" }
Conditionals can be used inside of recipes:
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:
foo := if "hello" == "goodbye" {
"xyz"
} else if "a" == "a" {
"abc"
} else {
"123"
}
bar:
@echo {{foo}}
$ just bar
abc
Stopping execution with error
Execution can be halted with the error
function. For example:
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.
os := "linux"
test: build
./test --test {{os}}
build:
./build {{os}}
$ just
./build linux
./test --test linux
Any number of arguments of the form NAME=VALUE
can be passed before recipes:
$ just os=plan9
./build plan9
./test --test plan9
Or you can use the --set
flag:
$ 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:
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:
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.
export WORLD := "world"
# This backtick will fail with "WORLD: unbound variable"
BAR := `echo hello $WORLD`
# Running `just a foo` will fail with "A: unbound variable"
a $A $B=`echo $A`:
echo $A $B
When export is set, all just
variables are exported as environment
variables.
Unexporting Environment Variables<sup>1.29.0</sup>
Environment variables can be unexported with the unexport keyword
:
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.
print_home_folder:
echo "HOME is: '${HOME}'"
$ 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.
Recipe Parameters
Recipes may have parameters. Here recipe build
has a parameter called
target
:
build target:
@echo 'Building {{target}}…'
cd {{target}} && make
To pass arguments on the command line, put them after the recipe name:
$ 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:
default: (build "main")
build target:
@echo 'Building {{target}}…'
cd {{target}} && make
Variables can also be passed as arguments to dependencies:
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:
build target:
@echo "Building {{target}}…"
push target: (build target)
@echo 'Pushing {{target}}…'
Parameters may have default values:
default := 'all'
test target tests=default:
@echo 'Testing {{target}}:{{tests}}…'
./test --tests {{tests}} {{target}}
Parameters with default values may be omitted:
$ just test server
Testing server:all…
./test --tests all server
Or supplied:
$ 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:
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:
backup +FILES:
scp {{FILES}} me@server.com:
Variadic parameters prefixed with +
accept one or more arguments and expand
to a string containing those arguments separated by spaces:
$ just backup FAQ.md GRAMMAR.md
scp FAQ.md GRAMMAR.md me@server.com:
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:
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:
test +FLAGS='-q':
cargo test {{FLAGS}}
{{…}}
substitutions may need to be quoted if they contain spaces. For
example, if you have the following recipe:
search QUERY:
lynx https://www.google.com/?q={{QUERY}}
And you type:
$ 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:
search QUERY:
lynx 'https://www.google.com/?q={{QUERY}}'
Parameters prefixed with a $
will be exported as environment variables:
foo $bar:
echo $bar
Dependencies
Dependencies run before recipes that depend on them:
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:
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:
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:
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 &&
:
a:
echo 'A!'
b: a && c d
echo 'B!'
c:
echo 'C!'
d:
echo 'D!'
…running b prints:
$ 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
:
a:
echo 'A!'
b: a
echo 'B start!'
just c
echo 'B end!'
c:
echo 'C!'
…running b prints:
$ 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:
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!"
$ 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:
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)]
<sup>1.32.0</sup> 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 := […]
<sup>1.33.0</sup>, 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
:
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
makesbash
exit if a command fails. -
set -u
makesbash
exit if a variable is undefined. -
set -x
makesbash
print each script line before it's run. -
set -o pipefail
makesbash
exit if a command in a pipeline fails. This isbash
-specific, so isn't turned on in normal linewisejust
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.
For example, to execute this recipe on Windows:
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:
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:
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:
foo:
#!/usr/bin/env bash
set -euxo pipefail
x=hello
echo $x
Sharing Environment Variables Between Recipes
Each line of each recipe is executed by a fresh shell, so it is not possible to share environment variables between recipes.
Using Python Virtual Environments
Some tools, like Python's venv,
require loading environment variables in order to work, making them challenging
to use with just
. As a workaround, you can execute the virtual environment
binaries directly:
venv:
[ -d foo ] || python3 -m venv foo
run: venv
./foo/bin/python3 main.py
Changing the Working Directory in a Recipe
Each recipe line is executed by a new shell, so if you change the working directory on one line, it won't have an effect on later lines:
foo:
pwd # This `pwd` will print the same directory…
cd bar
pwd # …as this `pwd`!
There are a couple ways around this. One is to call cd
on the same line as
the command you want to run:
foo:
cd bar && pwd
The other is to use a shebang recipe. Shebang recipe bodies are extracted and
run as scripts, so a single shell instance will run the whole thing, and thus a
pwd
on one line will affect later lines, just like a shell script:
foo:
#!/usr/bin/env bash
set -euxo pipefail
cd bar
pwd
Indentation
Recipe lines can be indented with spaces or tabs, but not a mix of both. All of
a recipe's lines must have the same type of indentation, but different recipes
in the same justfile
may use different indentation.
Each recipe must be indented at least one level from the recipe-name
but
after that may be further indented.
Here's a justfile with a recipe indented with spaces, represented as ·
, and
tabs, represented as →
.
set windows-shell := ["pwsh", "-NoLogo", "-NoProfileLoadTime", "-Command"]
set ignore-comments
list-space directory:
··#!pwsh
··foreach ($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 ""
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
:
conditional:
if true; then
echo 'True!'
fi
The extra leading whitespace before the second line of the conditional
recipe
will produce a parse error:
$ 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
conditional:
if true; then echo 'True!'; fi
conditional:
if true; then \
echo 'True!'; \
fi
conditional:
#!/usr/bin/env sh
if true; then
echo 'True!'
fi
for
loops
for:
for file in `ls .`; do echo $file; done
for:
for file in `ls .`; do \
echo $file; \
done
for:
#!/usr/bin/env sh
for file in `ls .`; do
echo $file
done
while
loops
while:
while `server-is-dead`; do ping -c 1 server; done
while:
while `server-is-dead`; do \
ping -c 1 server; \
done
while:
#!/usr/bin/env sh
while `server-is-dead`; do
ping -c 1 server
done
Outside Recipe Bodies
Parenthesized expressions can span multiple lines:
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 whitespace<sup>1.15.0</sup>:
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.
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:
$ 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:
$ export JUST_UNSTABLE=1
$ just
Is equivalent to:
$ 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
:
test: _test-helper
./bin/test
_test-helper:
./bin/super-secret-test-helper-stuff
$ just --list
Available recipes:
test
And from just --summary
:
$ just --summary
test
The [private]
attribute<sup>1.10.0</sup> may also be used to hide recipes or
aliases without needing to change the name:
[private]
foo:
[private]
alias b := bar
bar:
$ 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:
@quiet:
echo hello
echo goodbye
@# all done!
Now only the lines starting with @
will be echoed:
$ just quiet
hello
goodbye
# all done!
All recipes in a Justfile can be made quiet with set quiet
:
set quiet
foo:
echo "This is quiet"
@foo2:
echo "This is also quiet"
The [no-quiet]
attribute overrides this setting:
set quiet
foo:
echo "This is quiet"
[no-quiet]
foo2:
echo "This is not quiet"
Shebang recipes are quiet by default:
foo:
#!/usr/bin/env bash
echo 'Foo!'
$ just foo
Foo!
Adding @
to a shebang recipe name makes just
print the recipe before
executing it:
@bar:
#!/usr/bin/env bash
echo 'Bar!'
$ 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]
<sup>1.7.0</sup>
attribute. You may find this especially useful with a recipe that wraps a tool:
git *args:
@git {{args}}
$ 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:
[no-exit-message]
git *args:
@git {{args}}
$ 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:
default:
@just --choose
Invoking justfile
s in Other Directories
If the first argument passed to just
contains a /
, then the following
occurs:
-
The argument is split at the last
/
. -
The part before the last
/
is treated as a directory.just
will start its search for thejustfile
there, instead of in the current directory. -
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:
$ (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:
$ 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
:
import 'foo/bar.just'
a: b
@echo A
And the following text in foo/bar.just
:
b:
@echo B
foo/bar.just
will be included in justfile
and recipe b
will be defined:
$ 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:
import? 'foo/bar.just'
Missing source files for optional imports do not produce an error.
Modules<sup>1.19.0</sup>
A justfile
can declare modules using mod
statements.
mod
statements were stabilized in just
<sup>1.31.0</sup>. 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
:
mod bar
a:
@echo A
And the following text in bar.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:
$ just bar b
B
Or with path syntax:
$ 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:
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:
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:
mod? foo 'bar.just'
mod? foo 'baz.just'
Modules may be given doc comments which appear in --list
output<sup>1.30.0</sup>:
# foo is a great module!
mod foo
$ 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 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:
$ cat > script <<EOF
#!/usr/bin/env just --justfile
foo:
echo foo
EOF
$ chmod +x script
$ ./script foo
echo foo
foo
When a script with a shebang is executed, the system supplies the path to the
script as an argument to the command in the shebang. So, with a shebang of
#!/usr/bin/env just --justfile
, the command will be /usr/bin/env just --justfile PATH_TO_SCRIPT
.
With the above shebang, just
will change its working directory to the
location of the script. If you'd rather leave the working directory unchanged,
use #!/usr/bin/env just --working-directory . --justfile
.
Note: Shebang line splitting is not consistent across operating systems. The
previous examples have only been tested on macOS. On Linux, you may need to
pass the -S
flag to env
:
#!/usr/bin/env -S just --justfile
default:
echo foo
Formatting and dumping justfile
s
Each justfile
has a canonical formatting with respect to whitespace and
newlines.
You can overwrite the current justfile with a canonically-formatted version
using the currently-unstable --fmt
flag:
$ cat justfile
# A lot of blank lines
some-recipe:
echo "foo"
$ just --fmt --unstable
$ cat justfile
# A lot of blank lines
some-recipe:
echo "foo"
Invoking just --fmt --check --unstable
runs --fmt
in check mode. Instead of
overwriting the justfile
, just
will exit with an exit code of 0 if it is
formatted correctly, and will exit with 1 and print a diff if it is not.
You can use the --dump
command to output a formatted version of the
justfile
to stdout:
$ just --dump > 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
:
set fallback
foo:
echo foo
And the parent directory contains this justfile
:
bar:
echo bar
$ just bar
Trying ../justfile
echo bar
bar
Avoiding Argument Splitting
Given this justfile
:
foo argument:
touch {{argument}}
The following command will create two files, some
and argument.txt
:
$ 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:
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:
set positional-arguments
foo argument:
touch "$1"
This defeats just
's ability to catch typos, for example if you type $2
instead of $1
, but works for all possible values of argument
, including
those with double quotes.
Exported Arguments
All arguments are exported when the export
setting is set:
set export
foo argument:
touch "$argument"
Or individual arguments may be exported by prefixing them with $
:
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:
- The
--shell
and--shell-arg
command line options. Passing either of these will causejust
to ignore any settings in the current justfile. set windows-shell := [...]
set windows-powershell
(deprecated)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:
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
for details.
Changelog
A changelog for the latest release is available in
CHANGELOG.md.
Changelogs for previous releases are available on
the releases page. just --changelog
can also be used to make a just
binary print its changelog.
Miscellanea
Re-running recipes when files change
watchexec
can re-run any command
when files change.
To re-run the recipe foo
when any file changes:
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:
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:
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.
The just
binary can also generate the same completion scripts at runtime
using just --completions SHELL
:
$ 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:
# 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
, a venerable markup
language and one of the first practical applications of Unix. If you have
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.
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.
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:
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:
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:
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:
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:
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:
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: The Unix build tool
that inspired
just
. There are a few different modern day descendents of the originalmake
, including FreeBSD Make and GNU Make. - task: A YAML-based command runner written in Go.
- maid: A Markdown-based command runner written in JavaScript.
- microsoft/just: A JavaScript-based command runner written in JavaScript.
- cargo-make: A command runner for Rust projects.
- mmake: A wrapper around
make
with a number of improvements, including remote includes. - robo: A YAML-based command runner written in Go.
- mask: A Markdown-based command runner written in Rust.
- makesure: A simple and portable command runner written in AWK and shell.
- haku: A make-like command runner written in Rust.
Contributing
just
welcomes your contributions! just
is released under the maximally
permissive
CC0 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 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, live alongside the code
being tested, and test code in isolation. Integration tests are in the tests
directory 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,
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
-
Make sure the feature is wanted. There should be an open issue about the feature with a comment from @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. -
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.
-
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 withcargo install cargo-watch
and runningjust watch test
. -
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, or add a new file in tests and add a
mod
statement importing that file in tests/lib.rs. -
Implement the feature.
-
Run
just ci
to make sure that all tests, lints, and checks pass. -
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.
-
Incorporate feedback.
-
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
-
Write a new integration test in tests/attributes.rs.
-
Add a new variant to the
Attribute
enum. -
Implement the functionality of the new attribute.
-
Run
just ci
to make sure that all tests pass.
Janus
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:
test:
./test
make
will refuse to run your tests:
$ 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,
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 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
,
or some of the
justfile
s
out in the wild.
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!
😸