🤖 Just a command runner

Casey Rodarmor

Last update: Jan 8, 2023

Related tags

Development tools just

Overview

`just`

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

(非官方中文文档,这里,快看过来!)

Commands, called recipes, are stored in a file called justfile with syntax inspired by make:

build:
    cc *.c -o main

# test everything
test-all: build
    ./test --all

# run a specific test
test TEST: build
    ./test --test {{TEST}}

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 of Make’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 the Justfile.
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!

Manual

Installation
Quick Start
Examples
Features
Miscellanea
Contributing
- Janus
Frequently Asked Questions
- What are the idiosyncrasies of Make that Just avoids?
- What’s the relationship between just and cargo build scripts?
Further Ramblings

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, and Cygwin.

If you’d rather not install sh, you can use the shell setting to use the shell of your choice.

Like cmd.exe:

# use cmd.exe instead of sh:
set shell := ["cmd.exe", "/c"]

list:
  dir

…or Powershell:

# use Powershell instead of sh:
set shell := ["powershell.exe", "-c"]

hello:
  Write-Host "Hello, world!"

Packages

Operating System	Package Manager	Package	Command
Various	Cargo	just	`cargo install just`
Microsoft Windows	Scoop	just	`scoop install just`
macOS	Homebrew	just	`brew install just`
macOS	MacPorts	just	`port install just`
Arch Linux	Yay	just ^AUR	`yay -S just`
NixOS, Linux, macOS	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`

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

Quick Start

See Installation for how to install just on your computer. Try running just --version to make sure that it’s installed correctly.

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.

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 '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 example justfiles can be found in the examples directory.

Features

Listing Available Recipes

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

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

Aliases

Aliases allow recipes to be invoked with alternative names:

alias b := build

build:
  echo 'Building!'

$ just b
build
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	Description
`shell`	`[COMMAND, ARGS…]`	Set the command used to invoke recipes and evaluate backticks.

Shell

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}}")

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

Variables and Substitution

Variables, strings, concatenation, and substitution using {{…}} are supported:

version := "0.2.7"
tardir  := "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}}

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!'}}'

Strings

Double-quoted strings support escape sequences:

string-with-tab             := "\t"
string-with-newline         := "\n"
string-with-carriage-return := "\r"
string-with-double-quote    := "\""
string-with-slash           := "\\"

$ just --evaluate
"tring-with-carriage-return := "
string-with-double-quote    := """
string-with-newline         := "
"
string-with-slash           := "\"
string-with-tab             := "     "

Single-quoted strings do not recognize escape sequences and may contain line breaks:

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

line-breaks := 'hello
this
is
  a
     raw
string!
'

$ just --evaluate
escapes := "\t\n\r\"\\"

line-breaks := "hello
this
is
  a
     raw
string!
"

Ignoring Errors

Normally, if a command returns a nonzero 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.

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".
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

Environment Variables

env_var(key) – Retrieves the environment variable with name key, aborting if it is not present.
env_var_or_default(key, default) – Retrieves the environment variable with name key, returning default if it is not present.

Invocation Directory

invocation_directory() - Retrieves the path of the current working directory, before just 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 and Justfile Directory

justfile() - Retrieves the path of the current justfile.
justfile_directory() - Retrieves the path of the parent directory of the current justfile.

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

script:
  ./{{justfile_directory()}}/scripts/some_script

Dotenv Integration

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:

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

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

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
abc

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.

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

Environment 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

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

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 must be parenthesized:

arch := "wasm"

test triple=(arch + "-unknown-unknown"):
  ./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 contains 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}}'

Running recipes at the end of a recipe

Dependencies of a recipes always run before a recipe starts. That is to say, the dependee always runs before the depender.

You can call Just recursively to run a recipe after a recipe ends. Given the following justfile:

a:
  echo 'A!'

b: a
  echo 'B!'
  just c

c:
  echo 'C!'

…running 'b' prints:

$ just b
echo 'A!'
A!
echo 'B!'
B!
echo 'C!'
C!

This has some 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.

Writing Recipes in Other Languages

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!"

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!

Safer Bash Shebang Recipes

If you’re writing a Bash shebang recipe, consider adding set -euxo pipefail:

foo:
    #!/usr/bin/env bash
    set -euxo pipefail
    hello='Yo'
    echo "$hello from Bash!"

It isn’t strictly necessary, but set -euxo pipefail turns on a few useful features that make Bash shebang recipes behave more like normal, linewise Just recipe:

set -e makes bash exit if a command fails.
set -u makes bash exit if a variable is undefined.
set -x makes bash print each script line before it’s run.
set -o pipefail makes bash exit if a command in a pipeline fails.

Together, these avoid a lot of shell scripting gotchas.

Shebang Recipe Execution on Windows

On Windows, shebang interpreter paths containing a / are translated from Unix-style paths to Windows-style paths using cygpath, a utility that ships with Cygwin.

For example, to execute this recipe on Windows:

echo:
  #!/bin/sh

  echo "Hello!"

The interpreter path /bin/sh will be translated to a Windows-style path using cygpath before being executed.

If the interpreter path does not contain a / it will be executed without being translated. This is useful if cygpath is not available, or you wish to use a Windows style path to the interpreter.

Setting Variables in a Recipe

Recipe lines are interpreted by the shell, not Just, so it’s not possible to set Just variables in the middle of a recipe:

foo:
  x := "hello" # This doesn't work!
  echo {{x}}

It is possible to use shell variables, but there’s another problem. Every recipe line is run by a new shell instance, so variables set in one line won’t be set in the next:

foo:
  x=hello && echo $x # This works!
  y=bye
  echo $y            # This doesn't, `y` is undefined here!

The best way to work around this is to use a shebang recipe. Shebang recipe bodies are extracted and run as scripts, so a single shell instance will run the whole thing:

foo:
  #!/usr/bin/env bash
  set -euxo pipefail
  x=hello
  echo $x

Changing the Working Directory in a Recipe

Each recipe line is executed by a new shell, so if you change the working directory on one line, it won’t have an effect on later lines:

foo:
  pwd    # This `pwd` will print the same directory…
  cd bar
  pwd    # …as this `pwd`!

There are a couple ways around this. One is to call cd on the same line as the command you want to run:

foo:
  cd bar && pwd

The other is to use a shebang recipe. Shebang recipe bodies are extracted and run as scripts, so a single shell instance will run the whole thing, and thus a pwd on one line will affect later lines, just like a shell script:

foo:
  #!/usr/bin/env bash
  set -euxo pipefail
  cd bar
  pwd

Multi-line Constructs

Recipes without an initial shebang are evaluated and run line-by-line, which means that multi-line constructs probably won’t do what you want.

For example, with the following justfile:

conditional:
    if true; then
        echo 'True!'
    fi

The extra leading whitespace before the second line of the conditional recipe will produce a parse error:

$ just conditional
error: Recipe line has extra leading whitespace
  |
3 |         echo 'True!'
  |     ^^^^^^^^^^^^^^^^

To work around this, you can write conditionals on one line, escape newlines with slashes, or add a shebang to your recipe. Some examples of multi-line constructs are provided for reference.

`if` statements

conditional:
    if true; then echo 'True!'; fi

conditional:
    if true; then \
        echo 'True!'; \
    fi

conditional:
    #!/usr/bin/env sh
    if true; then
        echo 'True!'
    fi

`for` loops

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

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

for:
    #!/usr/bin/env sh
    for file in `ls .`; do
        echo $file
    done

`while` loops

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

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

while:
    #!/usr/bin/env sh
    while `server-is-dead`; do
        do ping -c 1 server
    done

Command Line Options

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.

Private Recipes

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

test: _test-helper
  ./bin/test

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

$ just --list
Available recipes:
    test

And from just --summary:

$ just --summary
test

This is useful for helper recipes which are only meant to be used as dependencies of other recipes.

Quiet Recipes

A recipe name may be prefixed with '@' to invert the meaning of '@' before each line:

@quiet:
  echo hello
  echo goodbye
  @# all done!

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

$ 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                                                                                    ~/src/just
#!/usr/bin/env bash
echo 'Bar!'
Bar!

Selecting Recipes to Run With an Interactive Chooser

The --choose subcommand makes just invoke a chooser to select which recipes to run. Choosers should read lines containing recipe names from standard input and print one or more of those names separated by spaces to standard output.

Because there is currenly no way to run a recipe that requires arguments with --choose, such recipes will not be given to the chooser. Private recipes and aliases are also skipped.

The chooser can be overridden with the --chooser flag. If --chooser is not given, then just first checks if $JUST_CHOOSER is set. If it isn’t, then the chooser defaults to fzf, a popular fuzzy finder.

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

The chooser is invoked in the same way as recipe lines. For example, if the chooser is fzf, it will be invoked with sh -cu 'fzf', and if the shell, or the shell arguments are overridden, the chooser invocation will respect those overrides.

If you’d like just to default to selecting recipes with a chooser, you can use this as your default recipe:

default:
  @just --choose

Invoking Justfiles in Other Directories

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

The argument is split at the last /.
The part before the last / is treated as a directory. Just will start its search for the justfile 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 Scripts

By adding a shebang line to the top of a justfile and making it executable, just can be used as an interpreter for scripts:

$ cat > script <<EOF
#!/usr/bin/env just --justfile

foo:
  echo foo
EOF
$ chmod +x script
$ ./script foo
echo foo
foo

When a script with a shebang is executed, the system supplies the path to the script as an argument to the command in the shebang. So, with a shebang of #!/usr/bin/env just --justfile, the command will be /usr/bin/env just --justfile PATH_TO_SCRIPT.

With the above shebang, just will change its working directory to the location of the script. If you’d rather leave the working directory unchanged, use #!/usr/bin/env just --working-directory . --justfile.

Note: Shebang line splitting is not consistent across operating systems. The previous examples have only been tested on macOS. On Linux, you may need to pass the -S flag to env:

#!/usr/bin/env -S just --justfile

default:
  echo foo

Miscellanea

Companion Tools

Tools that pair nicely with just include:

watchexec — a simple tool that watches a path and runs a command whenever it detects modifications.

GitHub Actions

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

Shell Alias

For lightning-fast command running, put alias j=just in your shell’s configuration file.

Shell Completion Scripts

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

Syntax Highlighting

justfile syntax is close enough to make that you may want to tell your editor to use make syntax highlighting for just.

Vim

For vim, 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

Vim and Emacs

Include the following in a justfile to enable syntax highlighting in vim and emacs:

# Local Variables:
# mode: makefile
# End:
# vim: set ft=make :

Visual Studio Code

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

Kakoune

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

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.

Grammar

A non-normative grammar of justfiles can be found in GRAMMAR.md.

just.sh

Before just was a fancy rust program it was a tiny shell script that called make. You can find the old version in extras/just.sh.

Non-Project Specific Justfile

If you want some commands to be available everywhere, put them in ~/.justfile and add the following to your shell’s initialization file:

alias .j='just --justfile ~/.justfile --working-directory ~'

Or, if you’d rather they run in the current directory:

alias .j='just --justfile ~/.justfile --working-directory .'

I’m pretty sure that nobody actually uses this feature, but it’s there.

¯\_(ツ)_/¯

Contributing

just welcomes your contributions! just is released under the maximally permissive CC0 public domain dedication and fallback license, so your changes must also released under this license.

Janus

Janus is a tool that collects and analyzes justfiles, and can determine if a new version of just breaks or changes the interpretation of existing justfiles.

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.

Frequently Asked Questions

What are the idiosyncrasies of Make that Just avoids?

Make has some behaviors which are confusing, complicated, or make it unsuitable for use as a general command runner.

One example is that under some circumstances, Make won’t actually run the commands in a recipe. For example, if you have a file called test and the following makefile:

test:
  ./test

Make will refuse to run your tests:

$ make test
make: `test' is up to date.

Make assumes that the test recipe produces a file called test. Since this file exists and the recipe has no other dependencies, Make thinks that it doesn’t have anything to do and exits.

To be fair, this behavior is desirable when using Make as a build system, but not when using it as a command runner. You can disable this behavior for specific targets using Make’s built-in .PHONY target name, but the syntax is verbose and can be hard to remember. The explicit list of phony targets, written separately from the recipe definitions, also introduces the risk of accidentally defining a new non-phony target. In just, all recipes are treated as if they were phony.

Other examples of Make’s idiosyncrasies include the difference between = and := in assignments, the confusing error messages that are produced if you mess up your makefile, needing $$ to use environment variables in recipes, and incompatibilities between different flavors of Make.

What’s the relationship between just and cargo build scripts?

Cargo build scripts have a pretty specific use, which is to control how cargo builds your rust project. This might include adding flags to rustc invocations, building an external dependency, or running some kind of codegen step.

just, on the other hand, is for all the other miscellaneous commands you might run as part of development. Things like running tests in different configurations, linting your code, pushing build artifacts to a server, removing temporary files, and the like.

Also, although just is written in rust, it can be used regardless of the language or build system your project uses.

Further Ramblings

I personally find it very useful to write a justfile for almost every project, big or small.

On a big project with multiple contributors, it’s very useful to have a file with all the commands needed to work on the project close at hand.

There are probably different commands to test, build, lint, deploy, and the like, and having them all in one place is useful and cuts down on the time you have to spend telling people which commands to run and how to type them.

And, with an easy place to put commands, it’s likely that you’ll come up with other useful things which are part of the project’s collective wisdom, but which aren’t written down anywhere, like the arcane commands needed for some part of your revision control workflow, 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 justfiles 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!

😸

Comments

Cross-platform justfiles
It would be useful to be able to write single justfiles that work on a variety of systems.

Concretely, justfile authors should be able to write a single justfile that can be deployed on different platforms, where the same command (i.e. just build) can be used to invoke the justfile and run a particular recipe or set of recipes.

I just released version v0.5.0 (see #530), which allows setting the shell used to interpret backticks and recipe lines on a per-justfile basis. This allows writing justfiles that work on platforms where sh is not available, but it still requires writing a different justfile for each different platform.

This feature has been discussed before, in particular in #326 and #161, however those issues have been addressed and closed, so I'm opening this issue to track the feature more directly.

The design which I currently favor is to add annotations to recipes that control:

Which shell is used: e.g "this recipe should be run with cmd.exe /c instead of sh -cu"

In which circumstances a recipe should run: e.g. "this recipe should be run when sh is not available"

Example:

[sh] foo: ls / [powershell] foo: dir C:\\

Since this feature is primarily intended to make just usable when sh is not available, it seems like different versions of the same recipe should be selected not based on which OS just is running on, but rather whether or a particular shell is available. (Since windows machines may have sh, and if sh is available it is probably desirable to use it.)

I suggest initially starting with three annotations, sh, powershell, and cmd. Each annotation has an associated test, which, if multiple recipes have the same name but different annotations, just will use to select which version should run.

| annotation | test | shell | | - | - | - | | sh | sh -cu echo OK | sh -cu | | cmd | cmd.exe /c Echo OK | cmd.exe /c | | powershell | powershell -c "Write-Host OK" | powershell -c |

Recipes with no annotation will default to sh, to preserve backwards compatibility.

I think the above design is solid, but there are still a couple of unresolved questions:

Should it be possible for the user to override recipe selection from the command line, e.g. to run a powershell-annotated recipe even if sh is available? If so how?

Should it be possible to specify that recipe selection should be based on OS, and not shell availability? If so, how is OS-detection performed? If a recipe must run OS-specific commands, for example, it might be desirable to select recipe variants based on OS, and not shell availability, and even have a windows-specific recipe that still uses sh.

enhancement large
opened by casey 36

Add ability to include other justfiles

Would it be possible to add file inclusion to Justfiles?

A semi-common pattern I have with makefiles is to use separate makefiles for different environments with a common Makefile included between them.

A trimmed down example I'm currently using is below. There are three files:

Makefile.include: Contains common configuration and targets.
Makefile.vagrant: Configuration and targets specific to the development install.
Makefile.staging: Configuration and targets specific to the cloud staging environment.

# Makefile.include  Common configuration and targets

ENVIRONMENT_TYPE ?= Default
INVENTORY ?= ./inventory
ANSIBLE_ARGS ?= --verbose
INSTALL_PLAYBOOK ?= playbooks/install.yml
DEPLOY_PLAYBOOK ?= playbooks/deploy.yml
UPGRADE_PLAYBOOK ?= playbooks/upgrade.yml
ANSIBLE = ansible-playbook $(ANSIBLE_ARGS) --inventory=$(INVENTORY)

all: provision install deploy

install:
	$(ANSIBLE) $(INSTALL_PLAYBOOK)

deploy:
	$(ANSIBLE) $(DEPLOY_PLAYBOOK)

upgrade:
	$(ANSIBLE) $(UPGRADE_PLAYBOOK)

# Makefile.vagrant   Local installs using vagrant.
INVENTORY ?= .vagrant/provisioners/ansible/inventory/vagrant_ansible_inventory
ENVIRONMENT_TYPE = Vagrant

include Makefile.include

provision:
	vagrant up

nuke:
	vagrant destroy -f
	rm -rf .vagrant

# Makefile.staging  Build staging environment in the cloud
INVENTORY ?= ./inventory/gce.py

PROVISION_PLAYBOOK ?= gcloud/provision.yml
ENVIRONMENT_TYPE = Staging

include Makefile.include

provision:
	$(ANSIBLE) $(PROVISION_PLAYBOOK)
	./inventory/gce.py --refresh-cache > /dev/null

nuke:
	$(ANSIBLE) gcloud/teardown.yml

If you have a better suggestion for solving my use case that doesn't include multiple files, I'm all ears. I'm always happy to learn. :smiley:

enhancement large

opened by cledoux 35

Add usage gif to README

Fixes #916

Like we briefly discussed in the issue; asciinema is a nice tool, but it's not suitable for embedding in READMEs. I'm using asciinema/asciicast2gif to convert to a gif. Is this in line with what you're looking for? Where do you want it in the README?

If you could do me a favor, toss the "hacktoberfest" label on the issue and PR. ;)
hacktoberfest-accepted

opened by Celeo 30
Consider requiring a statement in justfile to load .env file
If you're here because of a warning, sorry for the inconvenience!

When just 1.0 is released, it will stop loading .env files by default. Automatically loading .env files seemed like it might lead to unexpected behavior, especially because .env files are often sitting around, and might be present locally but not present in production, or vice-versa.

In order to avoid unexpected breakages, just will issue a warning if a .env file is found, but dotenv-load, the setting that controls .env file loading, is not set. dotenv-load currently defaults to true, but will be changed to default to false.

To silence the warning and continue to load .env files, add the following to your justfile:

set dotenv-load := true

To silence the warning and no longer load .env files, add the following to your justfile:

set dotenv-load := false

You can also suppress the warning by seting the environment variable JUST_SUPPRESS_DOTENV_LOAD_WARNING to 1.

In order to give users plenty of time to update, the change will be made over multiple releases:

[x] 2021-03-28 v0.8.7 – Add dotenv-load setting

[x] 2021-07-28 v0.x.y – Warn if .env file loaded without dotenv-load being set.

[x] 2022-02-01 v1.0.0 – Change dotenv-load default to false.

This is probably a non-issue. But it strikes me that some users might be surprised when just loads their .env file. It might be wise to not load .env files by default, and let users opt-in with a setting, like so:

set load-dotenv := true

Of course, that would be a breaking change, so it's probably not worth it.

Update: I more and more think there's a bit too much magic and potential for unexpected behavior with automatic .env file loading, so I'm more leaning towards doing this.

I'd like to let users control:

Whether or not a dotenv file is loaded at all

The name of the dotenv file

Whether or not to search recursively up to the root for the dotenv file

Eventually, I'd like the default behavior to be to not load a dotenv file, unless the user asks for it with a setting in their justfile, or a command line argument.

In order to avoid disruption, we can have a transitionary period during which Just will emit a warning if it finds a .env file but there was no directive in the Justfile, suggesting that the user add a directive to load the .env file.

I'm eager to hear from people who would be annoyed by this change, i.e who would now have to write a statement to load a .env file.

As for the actual way of controlling these settings, here's an idea. Dotenv loading would be controlled by the following settings, shown with their default settings:

# control whether or not to load a dotenv file at all. defaults to `false`, so no dotenv file is loaded by default set dotenv-load := false # controls the file name of the dotenv file. defaults to `.env` set dotenv-name := ".env" # controls whether or not to search parent directories recursively, up to the root, defaults to `true` set dotenv-recursive := true

I'm not sure whether dotenv-recursive should be true or false by default. We should probably do whatever other dotenv implementations do by default.

As an additional convenience, if dotenv-name or dotenv-recursive are set in a justfile, dotenv-load will also be set to to true, if it isn't set explicitly to false.
enhancement good first issue
opened by casey 29
Supress the "error: Recipe `...` failed on line ... with exit code ..." without suppressing the exit code
If you're wrapping some binary CLI with just, e.g.

$ just some-command --some --flags

It will often return a non-zero exit code (e.g. 2) while you trying to browse through some arguments (especially if there's incomplete subcommands that have further nested subcommands etc). It's pretty annoying to have the error: Recipe...failed on line ... with exit code ... message pop up every time, making it feel somewhat alien.

Suppressing the error is not the right solution though, because it should remain to be a non-zero exit code! (especially if called from some scripts)

Is there a way to make just even more transparent and a bit more quiet? I.e., don't suppress exit codes but don't print anything extra to the output, at all (unless there's some fatal errors in the justfile itself).

// Apologies in advance if I'm missing something obvious here but I couldn't find anything except @ and -.
good first issue
opened by aldanor 27
Add support for generating shell completions

clap supports generating shell completions either at buildtime or at runtime. It would be helpful to add them. I'm willing to do the work on it, but I wanted to ask if you would prefer having a completions option to generate them at runtime, or a build script to generate them at compile time?
enhancement

opened by chrisvittal 26
How to invoke a virtual environment for Python on Windows with just?
Thank you for a great tool. It is fun and makes one productive.

I noticed calling a bacthc file on Windows fails:

λ just env-start call env1\Scripts\activate.bat sh: call: command not found

Any ideas how to fix?

In my justfile I have:

env-start: call env1\Scripts\activate.bat

call env1\Scripts\activate.bat passes on command line

Many thanks!
question
opened by epogrebnyak 24
Allow an alternative runner for shebang tasks
Currently the shell setting lets users customise the runner for single-line commands. But this doesn't affect shebang tasks. On Windows, the default shell may not exist, so this makes shebang tasks unusable. However, the "Python Launcher" shipped with Python includes a shebang interpreter, so it would be entirely possible on Windows to say

set shebang_shell := ["py"]

at the top of the justfile to get shebang support.

This should be a different setting variable, not shell, as py doesn't handle command lines, and a shell like Powershell doesn't handle shebangs. So a single setting won't work for both.

On an unrelated note, it would be nice to have systemwide settings, so that I didn't have to set shell (and shebang_shell, if it was added) in every justfile.
opened by pfmoore 23
Support cmd.exe on windows

Currently, just uses sh to execute all recipes on windows. This requires users to have installed sh, usually from cygwin or git-bash.

I would like to make this dependency optional. It should be possible for a user to create a justfile that uses cmd.exe to execute recipes.

I'm not sure the best way to indicate that a justfile uses cmd.exe for recipe execution, but my thought it to have just search for a file called justfile.com, and if it finds it use cmd.exe to execute all recipes within. It may be desirable to allow individual recipes to use cmd.exe, or to give some kind of syntax within a justfile, aside from the name, for using cmd.exe so all that is up in the air.

I don't know enough about windows to be able to do this, so I'm looking for help! If you're a windows dev and would like to implement this, do reach out!
enhancement

opened by casey 22
Add support for Snap
This partially fixes #429 by adding support for Snap.

Now you will have to create a Ubuntu account and then install Snapcraft from your terminal

sudo snap install snapcraft --classic => this should also install multipass or else it will ask for you to install

snapcraft login

snapcraft export-login file.txt - you might have to enter your username and password again

Create a GitHub secrets with SNAPCRAFT_LOGIN as your key and the values from the file.

You might probably want to try this on your local system. I think this should do it.
opened by akshaybabloo 21
allow bash completion to complete tasks in other directories

Today, I learned about just's ability to invoke justfiles in other directories.

I moved part of my tasks into ./ci/justfile. Then, with bash completion on, typed just ci/ + tab. It completed with files, not with just tasks.

This change here solves that problem.

If the current text being completed has a / char, we'll run a different just --summary command.

opened by jpbochi 20
Support including a justfile from another justfile

This PR adds support for including the contents of another justfile verbatim, using the syntax !include <path-to-file>. There is also some basic checking that justfiles cannot recursively include an already-processed justfile.

Should close https://github.com/casey/just/issues/1407

opened by neunenak 12
Avoid confusing released and unreleased features in docs
The docs in the readme and the docs at https://just.systems reflect the current master branch, not the current release, which is confusing. This came up most recently in #1467.

One possible solution is:

Only update the docs at just.systems on new releases, not on every change to master

Note at the beginning of the readme that the docs are for current mster, not the current release, and point users to the docs at just.systems for the current release documentation
opened by casey 0
Allow pass-through shell completion (if possible?)
I sometimes wrap a shell command with some extra steps in a justfile, and pass all extra arguments to that command. For example:

# set up some global environment vars init-env: # some magic init goes here [no-exit-message] git *ARGS: init-env git {{ARGS}}

This way I can run j git push, which would init some env vars, possibly other steps, and as the last step run the git push with any extra args I may pass in. It works great, but has no autocomplete in the shell.

It would be great if I could somehow indicate to just/shell that j git ... should use git autocomplete.
opened by nyurik 1
Feature Request: Support linting of shebang recipes
I like that just lets me put a lot of what I would normally write as a mass of shell scripts into a Justfile. But when recipe logic and documentation as code leads me to write a shebang recipe it is not long before I wish I could use a linter to make sure I have not blundered in writing that. Since most of my shebang recipes are using bash I personally would like some way to have just save a recipe to its temporary file and then, instead of executing it, have it run a locally installed linter like ShellCheck against that file. Those using other languages would likely need a way to specify their own linters of choice, however.

Implementation-wise, perhaps a new just variable linter could be defined as a companion to shell to specify the default linter for recipe lines.

As an initial implementation perhaps it would be sufficient to have a just --lint [recipe] option that would write the designated recipe's body to the "temporary file" and have just simply output the path to that for users to lint manually. That might enable the maximum flexibility for users and other tools that might incorporate just capabilities. Or maybe a --linter option would work similarly to --shell to invoke the designated linter on recipe bodies. Another possibility might have just recursively call itself to invoke lint: target: recipes. Maybe recipe attributes could be extended to cover different shebang languages, i.e.,

[bash] lint target: shellcheck {{target}} [python3] lint target: pylint {{target}}

where again, the target path would come from just's temporary path generation. Perhaps ~/.user.justfile is a mechanism to leverage to specify user preferences for shell/linter correspondences via a map/associative array or recipe attributes as above.

I could do something with junk -s [recipe] | tail -n +3 | shellcheck - but then I have to figure out how to deal with variable substitutions. I'm not a rust developer nor familiar with just internals so I'm spit-balling here as a happy just user wanting to be happier.

Finally, perhaps this request overlaps somewhat with #1094 Question: Language Server, though that seems to me like a much bigger ask. Thanks for considering it, and for just.
opened by JonathanDoughty 3
Feature Request: Unlisted aliases without a `_` prefix

I've been using just a lot lately. I have several commands that will let me deploy a game I'm working on to development hardware. So I have a recipe named launch-sdk.

But sometimes I don't remember if the recipe's name is launch-sdk or sdk-launch. There might be other synonyms I could've used as well; am I certain that I didn't name the recipe run-sdk, for instance?

And when I want to kill the process running on the SDK, I could use kill-sdk. Or maybe it was sdk-kill? sdk-terminate? stop-sdk?

That's what aliases are for, sure. But I have a lot of aliases, enough that they distract from actual recipes.

My proposed solution: The ability to specify that an alias should be unlisted without giving it an explicit _ prefix.

opened by JesseTG 4
an include feature for justfiles

This design takes all lines that look like this: @include "relative/path/to/file" and replaces them with the contents of the pointed-to file. The resulting buffer is passed along to be parsed and executed as before. That's it: no attempt to look at the file or do anything with the contents. This is pure concatenation.

Feel free to tweak as needed!

Implements #1407

opened by kbknapp 9