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Cheulong Sear
Cheulong Sear

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Justfile make your life easier

#just #ubuntu #programming #cli

What is Just?

just is a handy way to save and run project-specific commands.
Commands, called recipes, are stored in a file called justfile with syntax inspired by make.

Why use Just?

just gives you cleaner, safer, more portable project commands than ad-hoc shell scripts or long README copy-paste commands.

just has a ton of useful features, and many improvements over make:

  • just is a command runner, not a build system, so it avoids much of make's complexity and idiosyncrasies. No need for .PHONY recipes!

  • Linux, MacOS, Windows, and other reasonable unices are supported with no additional dependencies. (Although if your system doesn't have an sh, you'll need to choose a different shell.)

  • Errors are specific and informative, and syntax errors are reported along with their source context.

  • Recipes can accept command line arguments.

  • Wherever possible, errors are resolved statically. Unknown recipes and circular dependencies are reported before anything runs.

  • just loads .env files, making it easy to populate environment variables.

  • Recipes can be listed from the command line.

  • Command line completion scripts are available for most popular shells.

  • Recipes can be written in arbitrary languages, like Python or NodeJS.

And much more!

Installation

just should run on any system with a reasonable sh, including Linux, MacOS, and the BSDs.

For Ubuntu:

sudo apt install just
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Example

Here is the example of just with vitest in bun:

# sum.ts

console.log('environment is', process.env.NODE_ENV);

export const sum = (a: number, b: number) => {
    return a + b;
}

console.log(sum(1, 2));
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# sum.test.ts

import { expect, test } from 'vitest'
import { sum } from './sum.ts'

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3)
})
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  "scripts": {
    "start": "bun run sum.ts",
    "test": "vitest"
  }
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Create justfile in the root directory of the project:

default:
    just --list --unsorted

start:
    bun run start

test:
    vitest
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Run just:

just
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just start
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just test
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Other Arguments

Env

For example, if your .env file contains:

DATABASE_ADDRESS=localhost:6379
SERVER_PORT=1337
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And your justfile contains:

set dotenv-load

serve:
  @echo "Starting server with database $DATABASE_ADDRESS on port $SERVER_PORT…"
  ./server --database $DATABASE_ADDRESS --port $SERVER_PORT
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just serve will output:

$ just serve
Starting server with database localhost:6379 on port 1337…
./server --database $DATABASE_ADDRESS --port $SERVER_PORT
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### Export

The export setting causes all just variables to be exported as environment variables. Defaults to false.

set export

a := "hello"

@foo b:
  echo $a
  echo $b
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$ just foo goodbye
hello
goodbye
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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.

For example, running this recipe:

set positional-arguments

@foo bar:
  echo $0
  echo $1
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Will produce the following output:

$ just foo hello
foo
hello
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=== Done ===

Leave a comment if you have any questions.

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