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!
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.)
Operating System | Package Manager | Package | Command |
---|---|---|---|
Various | Cargo | just | cargo install just |
Microsoft Windows | Scoop | just | scoop install just |
Various | Homebrew | just | brew install just |
macOS | MacPorts | just | port install just |
Arch Linux | pacman | just | pacman -S just |
Various | Nix | just | nix-env -iA nixpkgs.just |
NixOS | Nix | just | nix-env -iA nixos.just |
Solus | eopkg | just | eopkg install just |
Void Linux | XBPS | just | xbps-install -S just |
FreeBSD | pkg | just | pkg install just |
Alpine Linux | apk-tools | just | apk add just |
Fedora Linux | DNF | just | dnf install just |
Gentoo Linux | Portage | dm9pZCAq/sys-devel/just |
eselect repository enable dm9pZCAq emerge --sync dm9pZCAq emerge sys-devel/just
|
Various | Conda | just | conda install -c conda-forge just |
Microsoft Windows | Chocolatey | just | choco install just |
Various | Snap | just | snap install --edge --classic just |
Various | asdf | just |
asdf plugin add just asdf install just <version>
|
Debian and Ubuntu derivatives | MPR | just |
git clone 'https://mpr.makedeb.org/just' cd just makedeb -si
|
Debian and Ubuntu derivatives | Prebuilt-MPR | just |
You must have the Prebuilt-MPR set up on your system in order to run this command.sudo apt install just
|
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
extractions/setup-just can be used to install just
in a GitHub Actions workflow.
Example usage:
- uses: extractions/setup-just@v1
with:
just-version: 0.8 # optional semver specification, otherwise latest
An RSS feed of just
releases is available here.
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.
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 gated behind the --unstable
flag. Features enabled by --unstable
may change in backwards incompatible ways at any time.
justfile
syntax is close enough to make
that you may want to tell your editor to use make
syntax highlighting for 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
vim-just
is also available from vim-polyglot, a multi-language Vim plugin.
tree-sitter-just is an Nvim Treesitter plugin for Neovim.
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 :
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:
An extension for VS Code by skellock is available here (repository).
You can install it from the command line by running:
code --install-extension skellock.just
A plugin for JetBrains IDEs by linux_china is available here.
Kakoune supports justfile
syntax highlighting out of the box, thanks to TeddyDD.
A syntax file for Sublime Text written by TonioGela is available in extras/just.sublime-syntax.
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.
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!
A variety of example justfile
s can be found in the examples directory.
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
Recipes can be listed in alphabetical order with just --list
:
$ just --list
Available recipes:
build
test
deploy
lint
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 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
Aliases allow recipes to be invoked with alternative names:
alias b := build
build:
echo 'Building!'
$ just b
build
echo 'Building!'
Building!
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
Name | Value | Description |
---|---|---|
allow-duplicate-recipes |
boolean | Allow recipes appearing later in a justfile to override earlier recipes with the same name. |
dotenv-load |
boolean | Load a .env file, if present. |
export |
boolean | Export all variables as environment variables. |
positional-arguments |
boolean | Pass positional arguments. |
shell |
[COMMAND, ARGS…] |
Set the command used to invoke recipes and evaluate backticks. |
windows-powershell |
boolean | Use PowerShell on Windows as default shell. |
Boolean settings can be written as:
set NAME
Which is equivalent to:
set NAME := true
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
If dotenv-load
is true
, a .env
file will be loaded if present. Defaults to false
.
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
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
The shell
setting controls the command used to invoke recipe lines and backticks. Shebang recipes are unaffected.
# 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.
just
uses sh
on Windows by default. To use a different shell on Windows, use windows-shell
:
set windows-shell := ["pwsh.exe", "-NoLogo", "-Command"]
hello:
Write-Host "Hello, world!"
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!"
set shell := ["python3", "-c"]
set shell := ["bash", "-uc"]
set shell := ["zsh", "-uc"]
set shell := ["fish", "-c"]
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.
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
If dotenv-load
is set, just
will load environment variables from a file named .env
. This file can be located in the same directory as your justfile
or in a parent directory. These 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
Variables, strings, concatenation, path joining, and substitution using {{…}}
are supported:
tmpdir := `mktemp`
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}}
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
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.
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!'
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 triple double-quotes, are supported. Indented string lines are stripped of 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\nbar\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 unindention algorithm does not take escape-sequence produced whitespace or newlines into account.
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!
just
provides a few built-in functions that might be useful when writing recipes.
-
arch()
— Instruction set architecture. Possible values are:"aarch64"
,"arm"
,"asmjs"
,"hexagon"
,"mips"
,"msp430"
,"powerpc"
,"powerpc64"
,"s390x"
,"sparc"
,"wasm32"
,"x86"
,"x86_64"
, and"xcore"
. -
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.
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.
invocation_directory()
- Retrieves the absolute path to the current directory whenjust
was invoked, beforejust
changed it (chdir'd) prior to executing commands.
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
-
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
just_executable()
- Absolute path to thejust
executable.
For example:
executable:
@echo The executable is at: {{just_executable()}}
$ just
The executable is at: /bin/just
-
lowercase(s)
- Converts
to lowercase. -
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
. -
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
. -
uppercase(s)
- Converts
to uppercase.
-
absolute_path(path)
- Absolute path to relativepath
in the working directory.absolute_path("./bar.txt")
in directory/foo
is/foo/bar.txt
. -
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.
-
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. -
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
.
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(message)
- Abort execution and report errormessage
to user.
sha256(string)
- Return the SHA-256 hash ofstring
as a hexadecimal string.sha256_file(path)
- Return the SHA-256 hash of the file atpath
as a hexadecimal string.uuid()
- Return a randomly generated UUID.
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.
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
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")
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
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 $B
When export is set, all just
variables are exported as environment variables.
Environment variables from the environment are passed automatically to the recipes.
print_home_folder:
echo "HOME is: '${HOME}'"
$ just
HOME is '/home/myuser'
just
will load environment variables from a .env
file if dotenv-load is set. The variables in the file will be available as environment variables to the recipes. See dotenv-integration for more information.
Environment variables can be propagated to just
variables using the functions env_var()
and env_var_or_default()
.
See environment-variables.
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
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
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 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!
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.
Recipes that start with a #!
are executed as scripts, so you can write recipes in other languages:
polyglot: python js perl sh ruby
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 = 'Yo'
echo $"($hello) from a shell 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!
Hello from ruby!
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.
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.
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
Each line of each recipe is executed by a fresh shell, so it is not possible to share environment variables between recipes.
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
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
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 indentation, but different recipes in the same justfile
may use different indentation.
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.
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:
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:
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
just
supports a number of useful command line options for listing, dumping, and debugging recipes and variable:
$ 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
Run just --help
to see all the options.
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
This is useful for helper recipes which are only meant to be used as dependencies of other 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:
$ j quiet
hello
goodbye
# all done!
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!
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
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/
just
looks for justfile
s named justfile
and .justfile
, which can be used to keep a justfile
hidden.
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
The --dump
command can be used with --dump-format json
to print a JSON representation of a justfile
. The JSON format is currently unstable, so the --unstable
flag is required.
If a recipe is not found, just
will look for justfile
s in the parent
directory and up, until it reaches the root directory.
This feature is currently unstable, and so must be enabled with the
--unstable
flag.
As an example, suppose the current directory contains this justfile
:
foo:
echo foo
And the parent directory contains this justfile
:
bar:
echo bar
$ just --unstable bar
Trying ../justfile
echo bar
bar
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.
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.
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 $2
, but works for all possible values of argument
, including those with double quotes.
All arguments are exported when the export
setting is set:
set export
foo argument:
touch "$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 $argumant
, but works for all possible values of argument
, including those with double quotes.
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.
Tools that pair nicely with just
include:
watchexec
— a simple tool that watches a path and runs a command whenever it detects modifications.
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 for Bash, Zsh, Fish, PowerShell, and Elvish are available in the completions directory. Please refer to your shell's documentation for how to install them.
The just
binary can also generate the same completion scripts at runtime, using the --completions
command:
$ just --completions zsh > just.zsh
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 "$(/opt/homebrew/bin/brew shellenv)"
fpath=($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
A non-normative grammar of justfile
s can be found in GRAMMAR.md.
Before just
was a fancy Rust program it was a tiny shell script that called make
. You can find the old version in extras/just.sh.
If you want some recipes to be available everywhere, you have a few options.
First, create a justfile
in ~/.user.justfile
with some recipes.
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.
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)_/¯
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 ~'
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')
There is no shortage of command runners out there! Some more or less similar alternatives to just
include:
- make: The Unix build tool that inspired
just
. - makesure: A simple and portable command runner written in AWK and shell.
- mmake: A wrapper around
make
with a number of improvements, including remote includes. - robo: A YAML-based command runner written in Go.
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.
Janus is a tool that collects and analyzes justfile
s, and can determine if a new version of just
breaks or changes the interpretation of existing justfile
s.
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.
The minimum supported Rust version, or MSRV, is Rust 1.47.0.
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
.
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.
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, 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!
😸