casey/just: Just a command runner
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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 are stored in a file called justfile
or 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 COMMAND
:
$ just test-all cc *.c -o main ./test --all Yay, all your tests passed!
just
produces detailed error messages and avoids make
’s idiosyncrasies, so debugging a justfile is easier and less surprising than debugging a makefile.
If you need help with just
please feel free to open an issue or let me know on gitter
. Feature requests and bug reports are always welcome!
Manual
Installation
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
.
Pre-built Binaries
Pre-built binaries for Linux, MacOS, and Windows can be found on the releases page .
You can use the following command to download the latest binary for MacOS or Windows, just replace DESTINATION_DIRECTORY
with the directory where you’d like to put just
:
curl -LSfs https://japaric.github.io/trust/install.sh | \ sh -s -- --git casey/just --to DESTINATION_DIRECTORY
On Linux, use:
curl -LSfs https://japaric.github.io/trust/install.sh | \ sh -s -- --git casey/just --target x86_64-unknown-linux-musl --to DESTINATION_DIRECTORY
Homebrew
On MacOS, just
can be installed using the Homebrew package manager
. Install Homebrew using the instructions here
, then run:
brew install just
Scoop
On Windows, just
can be installed using the Scoop package manager
. Install Scoop using the instractions here
, then run:
scoop install just
Arch Linux
On Arch Linux, just
is packaged as just
in AUR, the Arch User Repository
. Several tools are available to install packages from AUR, including yay
and yaourt
.
Nix
On NixOS, Linux, and MacOS, just
can be installed using the Nix package manager
. Install Nix
or NixOS
, then run:
nix-env -i just
Cargo
On Windows, Linux, and macOS, just
can be installed using Cargo, the rust language package manager
. Install Cargo using the instructions here
, then run:
cargo install just
(You might also need to add ~/.cargo/bin
to your shell’s $PATH
. If you can’t run just after installing it, put export PATH="$HOME/.cargo/bin:$PATH"
in your shell’s configuration file.)
Quick Start
Seefor 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 a justfile
in the current directory and upwards, so you can invoke it from any subdirectory of your project.
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!
Features
Listing Available Recipes
Recipes can be listed with just --list
:
$ just --list Available recipes: build test deploy lint
just --summary
is more concise:
$ just --summary build test deploy lint
Aliases
Aliases allow recipes to be invoked with alternative names:
alias b := build build: echo 'Building!'
$ just b build echo 'Building!' Building!
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! "
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 namekey
, aborting if it is not present. -
env_var_or_default(key, default)
– Retrieves the environment variable with namekey
, returningdefault
if it is not present.
Invocation Directory
-
invocation_directory()
- Retrieves the path of the current working directory, 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
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
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
Other recipes may not depend on a recipe with parameters.
To pass arguments, put them after the recipe name:
$ just build my-awesome-project Building my-awesome-project... cd my-awesome-project && 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 a +
before the argument name:
backup +FILES: scp {{FILES}} [email protected]:
Variadic parameters 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
A variadic parameter with a default argument will accept zero or more arguments:
commit MESSAGE +FLAGS='': git commit {{FLAGS}} -m "{{MESSAGE}}"
{{…}}
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}}'
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!
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!
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
.
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.
Shell Alias
For lightning-fast command running, put alias j=just
in your shell’s configuration file.
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,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]( https://creativecommons.org/publicdomain/zero/1.0/legalcode.txt
) public domain dedication and fallback license, so your changes must also released under this license.
Janus
[Janus]( https://github.com/casey/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 either confusing, complicated, or make it unsuitable for use as a general command runner.
One example is that sometimes make won’t run the commands in a recipe. For example, if you have a file called test
and the following makefile that runs it:
test: ./test
Make will actually refuse to run it:
$ make test make: `test' is up to date.
Make sees the recipe test
and assumes that it produces a file called test
. It then sees that this file exists and thus assumes that the recipe doesn’t need to be run.
To be fair, this behavior is desirable when using make as a build system, but not when using it as a command runner.
Some other examples include having to understand the difference between =
and :=
assignment, the confusing error messages that can be produced if you mess up your makefile, having to use $$
to write recipes that use environment variables, and incompatibilites 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 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!
:smile_cat:
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