just
just
is a handy way to save and run commands.
Commands are stored in a file called justfile
or Justfile
with syntax inspired by make
:
:
# test everything
: # run a specific test
:
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. Feature requests and bug reports are also always welcome!
installation
just
should run on any system with a reasonable sh
.
prebuilts
Prebuilt binaries for Linux and macOS can be found on the releases page.
cargo
Alternately, just
can be installed with cargo
, the rust language package manager:
- Install rust and cargo by following the instructions at rustup.rs
- Run
cargo install just
- Add
~/.cargo/bin
to your PATH
alias
You can put alias j=just
in your shell's config file for lighting fast command running.
How do I just?
Once just
is working, create a file called justfile
in the root of your project and start adding recipes to it.
Recipes look like this:
:
# this is a comment
:
Running just
with no arguments runs the first recipe in the justfile
:
When you invoke just
it looks for a justfile
in the current directory and upwards, so you can invoke just
from any subdirectory of your project.
One or more arguments specify the recipes to run:
just
prints each command to standard error before running it, which is why echo 'This is a recipe!'
was printed. Lines starting with @
will not be printed which is why echo 'Another recipe.'
was not printed.
A recipe name may be prefixed with '@' to invert the meaning of '@' before each line:
:
Now only the lines starting with '@' will be echoed:
# all done!
Recipes stop running if a command fails. Here cargo publish
will only run if cargo test
succeeds:
:
Recipes can depend on other recipes. Here the test
recipe depends on the build
recipe, so build
will run before test
:
:
: :
Recipes without dependencies will run in the order they're given on the command line:
Dependencies will always run first, even if they are passed after a recipe that depends on them:
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 justfile with the recipe build
, which is also the default recipe, the following are all equivalent:
&& )
Assignment, strings, concatination, and substitution with {{...}}
are supported:
version = tardir =
tarball =
:
{{...}}
substitutions may need to be quoted if they contains spaces. For example, if you have the following recipe:
:
And you type:
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:
:
Double-quoted strings support escape sequences:
string-with-tab = string-with-newline =
string-with-carriage-return =
string-with-double-quote =
string-with-slash =
Single-quoted strings do not recognize escape sequences and may contain line breaks:
escapes = line-breaks =
this
is
a
raw
string!
'
Recipes may have parameters. Here recipe build
has a parameter called target
:
:
Other recipes may not depend on a recipe with parameters.
To pass arguments, put them after the recipe name:
&&
Parameters may have default values:
:
Parameters with default values may be omitted:
Or supplied:
The last parameter to a recipe may be variadic, indicated with a +
before the argument name:
:
Variadic parameters accept one or more arguments and expand to a string containing those arguments separated by spaces:
Variables can be exported to recipes as environment variables:
export RUST_BACKTRACE =
:
Variables can also be overridden from the command line:
os = : :
You can pass any number of arguments of the form NAME=VALUE
before recipes:
Or you can use the --set
flag:
Backticks can be used to store the result of commands:
:
:
Recipes that start with a #!
are executed as scripts, so you can write recipes in other languages:
:
:
:
:
:
:
just
also supports a number of useful command line options for listing, dumping, and debugging recipes and variable:
#!/usr/bin/env perl
;
Run just --help
to see all the options.
miscellanea
syntax hilighting
justfile
syntax is close enough to make
that you may want to tell your editor to use make syntax hilighting 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 hilighting working in your editor of choice so that I may include them here.
justfile grammar
A description of the grammar of justfiles can be found in GRAMMAR.md.
just.sh
Before just
was a bloated rust program it was a tiny shell script that called make
. If you can't or would rather not install rust you can find the old version in extras/just.sh.
non-project specific justfile
If you want some commands to be available everwhere, put them in ~/.justfile
and add the following to your shell's initialization file:
Or, if you'd rather they run in the current directory:
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 contributers, 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!
😸