-`just` is a command runner, not a build system, so it avoids much of [`make`'s complexity and idiosyncrasies](#what-are-the-idiosyncrasies-of-make-that-just-avoids). 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](#shell).)
If you need help with `just` please feel free to open an issue or ping me on [Discord](https://discord.gg/ezYScXR). Feature requests and bug reports are always welcome!
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](https://git-scm.com), [GitHub Desktop](https://desktop.github.com), or [Cygwin](http://www.cygwin.com).
You can also set the shell using command-line arguments. For example, to use PowerShell, launch `just` with `--shell powershell.exe --shell-arg -c`.
(PowerShell is installed by default on Windows 7 SP1 and Windows Server 2008 R2 S1 and later, and `cmd.exe` is quite fiddly, so PowerShell is recommended for most Windows users.)
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`:
`vim-just` is also available from [vim-polyglot](https://github.com/sheerun/vim-polyglot), a multi-language Vim plugin.
#### `tree-sitter-just`
[tree-sitter-just](https://github.com/IndianBoy42/tree-sitter-just) is an [Nvim Treesitter](https://github.com/nvim-treesitter/nvim-treesitter) plugin for Neovim.
Vim's built-in makefile syntax highlighting isn't perfect for `justfile`s, but it's better than nothing. You can put the following in `~/.vim/filetype.vim`:
[just-mode](https://github.com/leon-barrett/just-mode.el) provides syntax highlighting and automatic indentation of `justfile`s. It is available on [MELPA](https://melpa.org/) as [just-mode](https://melpa.org/#/just-mode).
An extension for VS Code by [skellock](https://github.com/skellock) is [available here](https://marketplace.visualstudio.com/items?itemName=skellock.just) ([repository](https://github.com/skellock/vscode-just)).
See [the installation section](#installation) for how to install `just` on your computer. Try running `just --version` to make sure that it's installed correctly.
The search for a `justfile` is case insensitive, so any case, like `Justfile`, `JUSTFILE`, or `JuStFiLe`, will work. `just` will also look for files with the name `.justfile`, in case you'd like to hide a `justfile`.
Running `just` with no arguments runs the first recipe in the `justfile`:
```sh
$ just
echo 'This is a recipe!'
This is a recipe!
```
One or more arguments specify the recipe(s) to run:
```sh
$ 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:
This [blog post](https://toniogela.dev/just/) discusses using `just` to improve management of shared machines, and includes a number of example `justfile`s.
When `just` is invoked without a recipe, it runs the first recipe in the `justfile`. This recipe might be the most frequently run command in the project, like running the tests:
The heading text can be customized with `--list-heading`:
```sh
$ just --list --list-heading $'Cool stuff…\n'
Cool stuff…
test
build
```
And the indentation can be customized with `--list-prefix`:
```sh
$ just --list --list-prefix ····
Available recipes:
····test
····build
```
The argument to `--list-heading` replaces both the heading and the newline following it, so it should contain a newline if non-empty. It works this way so you can suppress the heading line entirely by passing the empty string:
```sh
$ just --list --list-heading ''
test
build
```
### Aliases
Aliases allow recipes to be invoked with alternative names:
If `allow-duplicate-recipes` is set to `true`, defining multiple recipes with the same name is not an error and the last definition is used. Defaults to `false`.
The `export` setting causes all `just` variables to be exported as environment variables. Defaults to `false`.
```make
set export
a := "hello"
@foo b:
echo $a
echo $b
```
```sh
$ just foo goodbye
hello
goodbye
```
#### Positional Arguments
If `positional-arguments` is `true`, recipe arguments will be passed as positional arguments to commands. For linewise recipes, argument `$0` will be the name of the recipe.
When using an `sh`-compatible shell, such as `bash` or `zsh`, `$@` expands to the positional arguments given to the recipe, starting from one. When used within double quotes as `"$@"`, arguments including whitespace will be passed on as if they were double-quoted. That is, `"$@"` is equivalent to `"$1" "$2"`… When there are no positional parameters, `"$@"` and `$@` expand to nothing (i.e., they are removed).
The `shell` setting controls the command used to invoke recipe lines and backticks. Shebang recipes are unaffected.
```make
# use python3 to execute recipe lines and backticks
set shell := ["python3", "-c"]
# use print to capture result of evaluation
foos := `print("foo" * 4)`
foo:
print("Snake snake snake snake.")
print("{{foos}}")
```
`just` passes the command to be executed as an argument. Many shells will need an additional flag, often `-c`, to make them evaluate the first argument.
If `dotenv-load` is set to `true`, `just` will load environment variables from a file named `.env`. This file can be located in the same directory as your `justfile` or in a parent directory. These variables are environment variables, not `just` variables, and so must be accessed using `$VARIABLE_NAME` in recipes and backticks.
Single-quoted strings do not recognize escape sequences:
```make
escapes := '\t\n\r\"\\'
```
```sh
$ just --evaluate
escapes := "\t\n\r\"\\"
```
Indented versions of both single- and double-quoted strings, delimited by triple single- or triple double-quotes, are supported. Indented string lines are stripped of leading whitespace common to all non-blank lines:
```make
# this string will evaluate to `foo\nbar\n`
x := '''
foo
bar
'''
# this string will evaluate to `abc\n wuv\nbar\n`
y := """
abc
wuv
xyz
"""
```
Similar to unindented strings, indented double-quoted strings process escape sequences, and indented single-quoted strings ignore escape sequences. Escape sequence processing takes place after unindentation. The unindention algorithm does not take escape-sequence produced whitespace or newlines into account.
### Ignoring Errors
Normally, if a command returns a non-zero exit status, execution will stop. To continue execution after a command, even if it fails, prefix the command with `-`:
-`quote(s)` - Replace all single quotes with `'\''` and prepend and append single quotes to `s`. This is sufficient to escape special characters for many shells, including most Bourne shell descendants.
-`replace(s, from, to)` - Replace all occurrences of `from` in `s` to `to`.
-`trim(s)` - Remove leading and trailing whitespace from `s`.
-`trim_end(s)` - Remove trailing whitespace from `s`.
-`trim_end_match(s, pat)` - Remove suffix of `s` matching `pat`.
-`trim_end_matches(s, pat)` - Repeatedly remove suffixes of `s` matching `pat`.
-`trim_start(s)` - Remove leading whitespace from `s`.
-`trim_start_match(s, pat)` - Remove prefix of `s` matching `pat`.
-`trim_start_matches(s, pat)` - Repeatedly remove prefixes of `s` matching `pat`.
-`uppercase(s)` - Convert `s` to uppercase.
#### Path Manipulation
##### Fallible
-`extension(path)` - Extension of `path`. `extension("/foo/bar.txt")` is `txt`.
-`file_name(path)` - File name of `path` with any leading directory components removed. `file_name("/foo/bar.txt")` is `bar.txt`.
-`file_stem(path)` - File name of `path` without extension. `file_stem("/foo/bar.txt")` is `bar`.
-`parent_directory(path)` - Parent directory of `path`. `parent_directory("/foo/bar.txt")` is `/foo`.
-`without_extension(path)` - `path` without extension. `without_extension("/foo/bar.txt")` is `/foo/bar`.
These functions can fail, for example if a path does not have an extension, which will halt execution.
##### Infallible
-`join(a, b…)` - Join path `a` with path `b`. `join("foo/bar", "baz")` is `foo/bar/baz`. Accepts two or more arguments.
-`clean(path)` - Simplify `path` by removing extra path separators, intermediate `.` components, and `..` where possible. `clean("foo//bar")` is `foo/bar`, `clean("foo/..")` is `.`, `clean("foo/./bar")` is `foo/bar`.
### Command Evaluation Using Backticks
Backticks can be used to store the result of commands:
```make
localhost := `dumpinterfaces | cut -d: -f2 | sed 's/\/.*//' | sed 's/ //g'`
Regular expressions are provided by the [regex crate](https://github.com/rust-lang/regex), whose syntax is documented on [docs.rs](https://docs.rs/regex/1.5.4/regex/#syntax). Since regular expressions commonly use backslash escape sequences, consider using single-quoted string literals, which will pass slashes to the regex parser unmolested.
Conditional expressions short-circuit, which means they only evaluate one of their branches. This can be used to make sure that backtick expressions don't run when they shouldn't.
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:
`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`.
Parameters prefixed with a `$` will be exported as environment variables:
```make
foo $bar:
echo $bar
```
### Running Recipes at the End of a Recipe
Normal dependencies of a recipes always run before a recipe starts. That is to say, the dependee always runs before the depender. These dependencies are called "prior dependencies".
A recipe can also have subsequent dependencies, which run after the recipe and are introduced with an `&&`:
`just` doesn't support running recipes in the middle of another recipe, but you can call `just` recursively in the middle of a recipe. Given the following `justfile`:
This has limitations, since recipe `c` is run with an entirely new invocation of `just`: Assignments will be recalculated, dependencies might run twice, and command line arguments will not be propagated to the child `just` process.
### Writing Recipes in Other Languages
Recipes that start with a `#!` are executed as scripts, so you can write recipes in other languages:
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:
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](http://www.cygwin.com).
For example, to execute this recipe on Windows:
```make
echo:
#!/bin/sh
echo "Hello!"
```
The interpreter path `/bin/sh` will be translated to a Windows-style path using `cygpath` before being executed.
If the interpreter path does not contain a `/` it will be executed without being translated. This is useful if `cygpath` is not available, or you wish to pass a Windows-style path to the interpreter.
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:
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:
There are a couple ways around this. One is to call `cd` on the same line as the command you want to run:
```make
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:
The extra leading whitespace before the second line of the `conditional` recipe will produce a parse error:
```sh
$ 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.
### 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 currently no way to run a recipe that requires arguments with `--choose`, such recipes will not be given to the chooser. Private recipes and aliases are also skipped.
The chooser can be overridden with the `--chooser` flag. If `--chooser` is not given, then `just` first checks if `$JUST_CHOOSER` is set. If it isn't, then the chooser defaults to `fzf`, a popular fuzzy finder.
Arguments can be included in the chooser, i.e. `fzf --exact`.
The chooser is invoked in the same way as recipe lines. For example, if the chooser is `fzf`, it will be invoked with `sh -cu 'fzf'`, and if the shell, or the shell arguments are overridden, the chooser invocation will respect those overrides.
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:
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`:
The `--dump` command can be used with `--dump-format json` to print a JSON representation of a `justfile`. The JSON format is currently unstable, so the `--unstable` flag is required.
A changelog for the latest release is available in [CHANGELOG.md](CHANGELOG.md). Changelogs for previous releases are available on [the releases page](https://github.com/casey/just/releases). `just --changelog` can also be used to make a `just` binary print its changelog.
Miscellanea
-----------
### Companion Tools
Tools that pair nicely with `just` include:
- [`watchexec`](https://github.com/mattgreen/watchexec) — a simple tool that watches a path and runs a command whenever it detects modifications.
In `bash`, the aliased command may not keep the shell completion functionality described in the next section. Add the following line to your `.bashrc` to use the same completion function as `just` for your aliased command:
Shell completion scripts for Bash, Zsh, Fish, PowerShell, and Elvish are available in the [completions](completions) directory. Please refer to your shell's documentation for how to install them.
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](extras/just.sh).
If you want to call the recipes in `~/.user.justfile` by name, and don't mind creating an alias for every recipe, add the following to your shell's initialization script:
It took me way too long to realize that you could create recipe aliases like this. Notwithstanding my tardiness, I am very pleased to bring you this major advance in `justfile` technology.
You can customize the above aliases with additional options. For example, if you'd prefer to have the recipes in your `justfile` run in your home directory, instead of the current directory:
alias .j='just --justfile ~/.user.justfile --working-directory ~'
```
### Alternatives and Prior Art
There is no shortage of command runners out there! Some more or less similar alternatives to `just` include:
- [mmake](https://github.com/tj/mmake): A wrapper around `make` with a number of improvements, including remote includes.
- [robo](https://github.com/tj/robo): A YAML-based command runner written in Go.
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 be released under this license.
[Janus](https://github.com/casey/janus) is a tool that collects and analyzes `justfile`s, and can determine if a new version of `just` breaks or changes the interpretation of existing `justfile`s.
Before merging a particularly large or gruesome change, Janus should be run to make sure that nothing breaks. Don't worry about running Janus yourself, Casey will happily run it for you on changes that need it.
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:
`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](https://www.gnu.org/software/make/manual/html_node/Phony-Targets.html), but the syntax is verbose and can be hard to remember. The explicit list of phony targets, written separately from the recipe definitions, also introduces the risk of accidentally defining a new non-phony target. In `just`, all recipes are treated as if they were phony.
Other examples of `make`'s idiosyncrasies include the difference between `=` and `:=` in assignments, the confusing error messages that are produced if you mess up your makefile, needing `$$` to use environment variables in recipes, and incompatibilities between different flavors of `make`.
[`cargo` build scripts](http://doc.crates.io/build-script.html) 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.
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.
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`](justfile), or some of the `justfile`s [out in the wild](https://github.com/search?o=desc&q=filename%3Ajustfile&s=indexed&type=Code).
