rust-just-darwin-arm64
v1.35.0
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🤖 Just a command runner
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Readme
just
is a handy way to save and run project-specific commands.
This readme is also available as a book.
(ä¸ć–‡ć–‡ćˇŁĺś¨ 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
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
1.33.0 | [COMMAND, ARGS…]
| ['sh', '-eu']
| Set command used to invoke recipes with empty [script]
attribute. |
| shell
| [COMMAND, ARGS…]
| - | Set command used to invoke recipes and evaluate backticks. |
| tempdir
| string | - | Create temporary directories in tempdir
instead of the system default temporary directory. |
| unstable
1.31.0 | boolean | false
| Enable unstable features. |
| windows-powershell
| boolean | false
| Use PowerShell on Windows as default shell. (Deprecated. Use windows-shell
instead. |
| windows-shell
| [COMMAND, ARGS…]
| - | Set the command used to invoke recipes and evaluate backticks. |
| working-directory
1.33.0 | string | - | Set the working directory for recipes and backticks, relative to the default working directory. |
Boolean settings can be written as:
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.
The command-line option --dotenv-path
, short form -E
, can be used to set or
override dotenv-path
at runtime.
If dotenv-filename
is set just
will look for a file at the given path,
relative to the working directory and each of its ancestors.
If dotenv-filename
is not set, but dotenv-load
or dotenv-required
are
set, just will look for a file named .env
, relative to the working directory
and each of its ancestors.
dotenv-filename
and dotenv-path
are similar, but dotenv-path
is only
checked relative to the working directory, whereas dotenv-filename
is checked
relative to the working directory and each of its ancestors.
It is not an error if an environment file is not found, unless
dotenv-required
is set.
The loaded variables are environment variables, not just
variables, and so
must be accessed using $VARIABLE_NAME
in recipes and backticks.
For example, if your .env
file contains:
# 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]
attribute1.29.0:
[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}} [email protected]: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 constructed1.5.0:
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:
carriage-return := "\r"
double-quote := "\""
newline := "\n"
no-newline := "\
"
slash := "\\"
tab := "\t"
unicode-codepoint := "\u{1F916}"
$ just --evaluate
"arriage-return := "
double-quote := """
newline := "
"
no-newline := ""
slash := "\"
tab := " "
unicode-codepoint := "🤖"
The unicode character escape sequence \u{…}
master accepts up to
six hex digits.
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 expanded1.27.0:
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()
1.15.0 - Number of logical CPUs.os()
— Operating system. Possible values are:"android"
,"bitrig"
,"dragonfly"
,"emscripten"
,"freebsd"
,"haiku"
,"ios"
,"linux"
,"macos"
,"netbsd"
,"openbsd"
,"solaris"
, and"windows"
.os_family()
— Operating system family; possible values are:"unix"
and"windows"
.
For example:
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...)
1.27.0 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)
1.15.0 — Alias forenv_var(key)
.env(key, default)
1.15.0 — 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()
1.27.0 - Retrieves the path of the current source file.source_directory()
1.27.0 - Retrieves the path of the parent directory of the current source file.
source_file()
and source_directory()
behave the same as justfile()
and
justfile_directory()
in the root justfile
, but will return the path and
directory, respectively, of the current import
or mod
source file when
called from within an import or submodule.
Just Executable
just_executable()
- Absolute path to 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)
1.27.0 Appendsuffix
to whitespace-separated strings ins
.append('/src', 'foo bar baz')
→'foo/src bar/src baz/src'
prepend(prefix, s)
1.27.0 Prependprefix
to whitespace-separated strings ins
.prepend('src/', 'foo bar baz')
→'src/foo src/bar src/baz'
encode_uri_component(s)
1.27.0 - 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)
1.7.0 - Convert first character ofs
to uppercase and the rest to lowercase.kebabcase(s)
1.7.0 - Converts
tokebab-case
.lowercamelcase(s)
1.7.0 - Converts
tolowerCamelCase
.lowercase(s)
- Converts
to lowercase.shoutykebabcase(s)
1.7.0 - Converts
toSHOUTY-KEBAB-CASE
.shoutysnakecase(s)
1.7.0 - Converts
toSHOUTY_SNAKE_CASE
.snakecase(s)
1.7.0 - Converts
tosnake_case
.titlecase(s)
1.7.0 - Converts
toTitle Case
.uppercamelcase(s)
1.7.0 - 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)
1.24.0 - 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)
1.25.0 - Return BLAKE3 hash ofstring
as hexadecimal string.blake3_file(path)
1.25.0 - 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)
1.27.0 - 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)
1.30.0 - Return local time withformat
.datetime_utc(format)
1.30.0 - 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)
1.16.0 - Check whether a semanticversion
, e.g.,"0.1.0"
matches arequirement
, e.g.,">=0.1.0"
, returning"true"
if so and"false"
otherwise.
XDG Directories1.23.0
These functions return paths to user-specific directories for things like
configuration, data, caches, executables, and the user's home directory. These
functions follow the
XDG Base Directory Specification,
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
1.27.0 | "0123456789abcdef"
|
| HEXLOWER
1.27.0 | "0123456789abcdef"
|
| HEXUPPER
1.27.0 | "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]
1.17.0 | recipe | Require confirmation prior to executing recipe. |
| [confirm('PROMPT')]
1.23.0 | recipe | Require confirmation prior to executing recipe with a custom prompt. |
| [doc('DOC')]
1.27.0 | module, recipe | Set recipe or module's documentation comment to DOC
. |
| [extension('EXT')]
1.32.0 | recipe | Set shebang recipe script's file extension to EXT
. EXT
should include a period if one is desired. |
| [group('NAME')]
1.27.0 | module, recipe | Put recipe or module in in group NAME
. |
| [linux]
1.8.0 | recipe | Enable recipe on Linux. |
| [macos]
1.8.0 | recipe | Enable recipe on MacOS. |
| [no-cd]
1.9.0 | recipe | Don't change directory before executing recipe. |
| [no-exit-message]
1.7.0 | recipe | Don't print an error message if recipe fails. |
| [no-quiet]
1.23.0 | recipe | Override globally quiet recipes and always echo out the recipe. |
| [positional-arguments]
1.29.0 | recipe | Turn on positional arguments for this recipe. |
| [private]
1.10.0 | alias, recipe | Make recipe, alias, or variable private. See Private Recipes. |
| [script]
1.33.0 | recipe | Execute recipe as script. See script recipes for more details. |
| [script(COMMAND)]
1.32.0 | recipe | Execute recipe as a script interpreted by COMMAND
. See script recipes for more details. |
| [unix]
1.8.0 | recipe | Enable recipe on Unixes. (Includes MacOS). |
| [windows]
1.8.0 | recipe | Enable recipe on Windows. |
A recipe can have multiple attributes, either on multiple lines:
[no-cd]
[private]
foo:
echo "foo"
Or separated by commas on a single line1.14.0:
[no-cd, private]
foo:
echo "foo"
Enabling and Disabling Recipes1.8.0
The [linux]
, [macos]
, [unix]
, and [windows]
attributes are
configuration attributes. By default, recipes are always enabled. A recipe with
one or more configuration attributes will only be enabled when one or more of
those configurations is active.
This can be used to write justfile
s that behave differently depending on
which operating system they run on. The run
recipe in this justfile
will
compile and run main.c
, using a different C compiler and using the correct
output binary name for that compiler depending on the operating system:
[unix]
run:
cc main.c
./a.out
[windows]
run:
cl main.c
main.exe
Disabling Changing Directory1.9.0
just
normally executes recipes with the current directory set to the
directory that contains the justfile
. This can be disabled using the
[no-cd]
attribute. This can be used to create recipes which use paths
relative to the invocation directory, or which operate on the current
directory.
For example, this commit
recipe:
[no-cd]
commit file:
git add {{file}}
git commit
Can be used with paths that are relative to the current directory, because
[no-cd]
prevents just
from changing the current directory when executing
commit
.
Requiring Confirmation for Recipes1.17.0
just
normally executes all recipes unless there is an error. The [confirm]
attribute allows recipes require confirmation in the terminal prior to running.
This can be overridden by passing --yes
to just
, which will automatically
confirm any recipes marked by this attribute.
Recipes dependent on a recipe that requires confirmation will not be run if the relied upon recipe is not confirmed, as well as recipes passed after any recipe that requires confirmation.
[confirm]
delete-all:
rm -rf *
Custom Confirmation Prompt1.23.0
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 Variables1.29.0
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}} [email protected]:
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 [email protected]:
FAQ.md 100% 1831 1.8KB/s 00:00
GRAMMAR.md 100% 1666 1.6KB/s 00:00
Variadic parameters prefixed with *
accept zero or more arguments and
expand to a string containing those arguments separated by spaces, or an empty
string if no arguments are present:
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 nu