just
is a handy way to save and run project-specific commands.
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}}
just
produces detailed error messages and avoids make
âs 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!
- Installation
- Quick Start
- Features
- Listing Available Recipes
- Documentation Comments
- Variables and Substitution
- Strings
- Command Evaluation using Backticks
- Setting Variables from the Command Line
- Environment Variables
- Recipe Parameters
- Write Recipes in other Languages
- Command Line Options
- Private Recipes
- Quiet Recipes
- Invoking Justfiles in Other Directories
- Frequently Asked Questions
- Miscellanea
- Further Ramblings
just
should run on any system with a reasonable sh
.
On Windows, youâll need to install git or GitHub Desktop.
just
can be installed using cargo
, the rust language package manager:
-
Install rust and cargo by following the instructions here
-
Run
cargo install just
-
Add
~/.cargo/bin
to your shellâs $PATH.
rustup
may have done #3 for you. If this doesnât work, put export PATH="$HOME/.cargo/bin:$PATH"
in your shellâs configuration file
On MacOS, just
is a available through the Homebrew package manager. Install Homebrew using the instructions at https://brew.sh, then run:
brew install just
Pre-built binaries for Linux, macOS, and Windows can be found on the releases page.
See Installation for how to install just
on your computer. Try running just --version
to make sure that itâs 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
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 theyâre 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!
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
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, strings, concatenation, and substitution using {{âŚâ}}
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}}
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!
"
Backticks can be used to store the result of commands:
localhost = `dumpinterfaces | cut -d: -f2 | sed 's/\/.*//' | sed 's/ //g'`
serve:
./serve {{localhost}} 8080
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
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:
test target tests='all':
@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
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
{{âŚâ}}
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}}'
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!
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 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!
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 itâs 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/
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 wonât run the commands in a recipe. For example, if you have a file called test
and the 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 doesnât 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.
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.
For lightning-fast command running, put alias j=just
in your shellâs configuration file.
justfile
syntax is close enough to make
that you may want to tell your editor to use make syntax highlighting for just.
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
Include the following in a justfile
to enable syntax highlighting in vim and emacs:
# Local Variables:
# mode: makefile
# End:
# vim: set ft=make :
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.
A non-normative grammar of justfiles 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 commands to be available everwhere, put them in ~/.justfile
and add the following to your shellâs initialization file:
alias .j='just --justfile ~/.justfile --working-directory ~'
Or, if youâd rather they run in the current directory:
alias .j='just --justfile ~/.justfile --working-directory .'
Iâm pretty sure that nobody actually uses this feature, but itâs there.
ÂŻ\_(ă)_/ÂŻ
I personally find it very useful to write a justfile
for almost every project, big or small.
On a big project with multiple contributors, itâs 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, itâs likely that youâll come up with other useful things which are part of the projectâs collective wisdom, but which arenât written down anywhere, like the arcane commands needed for some part of your revision control workflow, install all your projectâs 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 itâs nice to be able to remember commands by name instead of ^Reverse searching your shell history, and itâs 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 projectâs justfile
, or some of the `justfile`s out in the wild.
Anyways, I think thatâs 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!
đ¸