452 lines
11 KiB
Markdown
452 lines
11 KiB
Markdown
just
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====
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[](https://crates.io/crates/just)
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[](https://travis-ci.org/casey/just)
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`just` is a handy way to save and run commands.
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Commands are stored in a file called `justfile` or `Justfile` with syntax inspired by `make`:
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```make
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build:
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cc *.c -o main
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# test everything
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test-all: build
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./test --all
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# run a specific test
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test TEST: build
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./test --test {{TEST}}
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```
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`just` produces detailed error messages and avoids `make`'s idiosyncrasies, so debugging a justfile is easier and less surprising than debugging a makefile.
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If you need help with `just` please feel free to send me an email. Feature requests and bug reports are also always welcome!
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getting started
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---------------
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`just` should run on any system with a reasonable `sh` and can be installed with `cargo`, the [rust language](https://www.rust-lang.org) package manager:
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1. Install rust and cargo by following the instructions at [rustup.rs](https://www.rustup.rs)
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2. Run `cargo install just`
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3. Add `~/.cargo/bin` to your PATH
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Optionally, you can also `alias j=just` for lighting fast command running.
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How do I just?
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--------------
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Once `just` is working, create a file called `justfile` in the root of your project and start adding recipes to it.
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Recipes look like this:
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```make
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recipe-name:
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echo 'This is a recipe!'
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# this is a comment
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another-recipe:
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@echo 'Another recipe.'
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```
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Running `just` with no arguments runs the first recipe in the `justfile`:
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```sh
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$ just
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echo 'This is a recipe!'
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This is a recipe!
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```
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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.
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One or more arguments specify the recipes to run:
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```sh
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$ just another-recipe
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Another recipe.
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```
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`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.
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A recipe name may be prefixed with '@' to invert the meaning of '@' before each line:
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```make
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@quiet:
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echo hello
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echo goodbye
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@# all done!
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```
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Now only the lines starting with '@' will be echoed:
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```sh
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$ j quiet
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hello
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goodbye
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# all done!
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```
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Recipes stop running if a command fails. Here `cargo publish` will only run if `cargo test` succeeds:
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```make
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publish:
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cargo test
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# tests passed, time to publish!
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cargo publish
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```
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Recipes can depend on other recipes. Here the `test` recipe depends on the `build` recipe, so `build` will run before `test`:
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```make
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build:
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cc main.c foo.c bar.c -o main
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test: build
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./test
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sloc:
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@echo "`wc -l *.c` lines of code"
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```
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```sh
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$ just test
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cc main.c foo.c bar.c -o main
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./test
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testing... all tests passed!
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```
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Recipes without dependencies will run in the order they're given on the command line:
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```sh
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$ just build sloc
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cc main.c foo.c bar.c -o main
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1337 lines of code
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```
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Dependencies will always run first, even if they are passed after a recipe that depends on them:
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```sh
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$ just test build
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cc main.c foo.c bar.c -o main
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./test
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testing... all tests passed!
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```
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Assignment, strings, concatination, and substitution with `{{...}}` are supported:
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```make
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version = "0.2.7"
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tardir = "awesomesauce-" + version
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tarball = tardir + ".tar.gz"
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publish:
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rm -f {{tarball}}
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mkdir {{tardir}}
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cp README.md *.c {{tardir}}
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tar zcvf {{tarball}} {{tardir}}
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scp {{tarball}} me@server.com:release/
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rm -rf {{tarball}} {{tardir}}
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```
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`{{...}}` substitutions may need to be quoted if they contains spaces. For example, if you have the following recipe:
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```make
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search QUERY:
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lynx https://www.google.com/?q={{QUERY}}
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```
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And you type:
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```sh
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$ just search "cat toupee"
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```
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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`.
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You can fix this by adding quotes:
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```make
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search QUERY:
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lynx 'https://www.google.com/?q={{QUERY}}'
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```
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Double-quoted strings support escape sequences:
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```make
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string-with-tab = "\t"
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string-with-newline = "\n"
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string-with-carriage-return = "\r"
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string-with-double-quote = "\""
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string-with-slash = "\\"
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```
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```sh
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$ just --evaluate
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"tring-with-carriage-return = "
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string-with-double-quote = """
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string-with-newline = "
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"
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string-with-slash = "\"
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string-with-tab = " "
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```
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Single-quoted strings do not recognize escape sequences and may contain line breaks:
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```make
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escapes = '\t\n\r\"\\'
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line-breaks = 'hello
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this
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is
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a
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raw
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string!
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'
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```
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```sh
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$ just --evaluate
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escapes = "\t\n\r\"\\"
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line-breaks = "hello
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this
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is
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a
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raw
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string!
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"
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```
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Recipes may have parameters. Here recipe `build` has a parameter called `target`:
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```make
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build target:
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@echo 'Building {{target}}...'
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cd {{target}} && make
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```
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Recipes with parameters have limitations. Other recipes may not depend on them, and only one recipe with parameters may be given on the command line.
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To pass arguments, put them after the recipe name:
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```sh
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$ just build my-awesome-project
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Building my-awesome-project...
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cd my-awesome-project && make
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```
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Parameters may have default values:
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```make
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test target tests='all':
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@echo 'Testing {{target}}:{{tests}}...'
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./test --tests {{tests}} {{target}}
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```
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Parameters with default values may be omitted:
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```sh
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$ just test server
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Testing server:all...
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./test --tests all server
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```
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Or supplied:
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```sh
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$ just test server unit
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Testing server:unit...
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./test --tests unit server
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```
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Variables can be exported to recipes as environment variables:
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```make
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export RUST_BACKTRACE = "1"
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test:
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# will print a stack trace if it crashes
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cargo test
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```
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Variables can also be overridden from the command line:
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```make
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os = "linux"
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test: build
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./test --test {{os}}
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build:
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./build {{os}}
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```
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```sh
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$ just
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./build linux
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./test --test linux
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```
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You can pass any number of arguments of the form `NAME=VALUE` before recipes:
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```sh
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$ just os=plan9
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./build plan9
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./test --test plan9
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```
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Or you can use the `--set` flag:
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```sh
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$ just --set os bsd
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./build bsd
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./test --test bsd
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```
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Backticks can be used to store the result of commands:
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```make
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localhost = `dumpinterfaces | cut -d: -f2 | sed 's/\/.*//' | sed 's/ //g'`
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serve:
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./serve {{localhost}} 8080
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```
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Recipes that start with a `#!` are executed as scripts, so you can write recipes in other languages:
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```make
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polyglot: python js perl sh ruby
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python:
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#!/usr/bin/env python3
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print('Hello from python!')
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js:
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#!/usr/bin/env node
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console.log('Greetings from JavaScript!')
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perl:
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#!/usr/bin/env perl
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print "Larry Wall says Hi!\n";
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sh:
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#!/usr/bin/env sh
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hello='Yo'
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echo "$hello from a shell script!"
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ruby:
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#!/usr/bin/env ruby
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puts "Hello from ruby!"
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```
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```sh
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$ just polyglot
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Hello from python!
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Greetings from JavaScript!
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Larry Wall says Hi!
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Yo from a shell script!
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Hello from ruby!
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```
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`just` also supports a number of useful command line options for listing, dumping, and debugging recipes and variable:
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```sh
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$ just --list
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Available recipes:
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js
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perl
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polyglot
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python
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ruby
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$ just --show perl
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perl:
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#!/usr/bin/env perl
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print "Larry Wall says Hi!\n";
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$ just --show polyglot
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polyglot: python js perl sh ruby
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```
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Run `just --help` to see all the options.
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miscellanea
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-----------
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### syntax hilighting
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`justfile` syntax is close enough to `make` that you may want to tell your editor to use make syntax hilighting for just.
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For vim, you can put the following in `~/.vim/filetype.vim`:
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```vimscript
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if exists("did_load_filetypes")
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finish
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endif
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augroup filetypedetect
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au BufNewFile,BufRead justfile setf make
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augroup END
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```
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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.
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### justfile grammar
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A description of the grammar of justfiles can be found in [GRAMMAR.md](GRAMMAR.md).
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### just.sh
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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](extras/just.sh).
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### non-project specific justfile
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If you want some commands to be available everwhere, put them in `~/.justfile` and add the following to your shell's initialization file:
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```sh
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alias .j='just --justfile ~/.justfile --working-directory ~'
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```
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Or, if you'd rather they run in the current directory:
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```sh
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alias .j='just --justfile ~/.justfile --working-directory .'
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```
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further ramblings
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-----------------
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I personally find it very useful to write a `justfile` for almost every project, big or small.
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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.
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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.
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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.
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Some ideas for recipes:
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* Deploying/publishing the project
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* Building in release mode vs debug mode
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* Running in debug mode or with logging enabled
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* Complex git workflows
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* Updating dependencies
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* Running different sets of tests, for example fast tests vs slow tests, or running them with verbose output
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* Any complex set of commands that you really should write down somewhere, if only to be able to remember them
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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.
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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?utf8=%E2%9C%93&q=filename%3Ajustfile).
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Anyways, I think that's about it for this incredibly long-winded README.
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I hope you enjoy using `just` and find great success and satisfaction in all your computational endeavors!
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😸
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