muskanmahajan37 / zx

A tool for writing better scripts

🐚 zx

#!/usr/bin/env zx

await $`cat package.json | grep name`

let branch = await $`git branch --show-current`
await $`dep deploy --branch=${branch}`

await Promise.all([
  $`sleep 1; echo 1`,
  $`sleep 2; echo 2`,
  $`sleep 3; echo 3`,
])

let name = 'foo bar'
await $`mkdir /tmp/${name}`

Bash is great, but when it comes to writing scripts, people usually choose a more convenient programming language. JavaScript is a perfect choice, but standard Node.js library requires additional hassle before using. zx package provides useful wrappers around child_process, escapes arguments and gives sensible defaults.

Install

npm i -g zx

Documentation

Write your scripts in a file with .mjs extension in order to be able to use await on top level. If you prefer .js extension, wrap your script in something like void async function () {...}().

Add next shebang at the beginning of your script:

#!/usr/bin/env zx

Now you will be able to run your script as:

chmod +x ./script.mjs
./script.mjs

Or via zx bin:

zx ./script.mjs

When using zx via bin or shebang, all $, cd, fetch, etc are available without imports.

$`command`

Executes given string using exec function from child_process package and returns Promise<ProcessOutput>.

let count = parseInt(await $`ls -1 | wc -l`)
console.log(`Files count: ${count}`)

Example. Upload files in parallel:

let hosts = [...]
await Promise.all(hosts.map(host =>
  $`rsync -azP ./src ${host}:/var/www`  
))

If executed program returns non-zero exit code, ProcessOutput will be thrown.

try {
  await $`exit 1`
} catch (p) {
  console.log(`Exit code: ${p.exitCode}`)
  console.log(`Error: ${p.stderr}`)
}

ProcessOutput

class ProcessOutput {
  readonly exitCode: number
  readonly stdout: string
  readonly stderr: string
  toString(): string
}

cd()

Changes working directory.

cd('/tmp')
await $`pwd` // outputs /tmp 

fetch()

This is a wrapper around node-fetch package.

let resp = await fetch('http://wttr.in')
if (resp.ok) {
  console.log(await resp.text())
}

question()

This is a wrapper around readline package.

type QuestionOptions = { choices: string[] }

function question(query?: string, options?: QuestionOptions): Promise<string>

Usage:

let username = await question('What is your username? ')
let token = await question('Choose env variable: ', {
  choices: Object.keys(process.env)
})

chalk package

The chalk package is available without importing inside scripts.

console.log(chalk.blue('Hello world!'))

fs package

The fs package is available without importing inside scripts.

let content = await fs.readFile('./package.json')

Promisified version imported by default. Same as if you write:

import {promises as fs} from 'fs'

os package

The os package is available without importing inside scripts.

await $`cd ${os.homedir()} && mkdir example`

$.shell

Specifies what shell is used. Default is which bash.

$.shell = '/usr/bin/bash'

$.prefix

Specifies command what will be added to all command.

Default is set -euo pipefail;.

$.quote

Specifies a function what will be used for escaping special characters in command substitution.

Default is shq package.

$.verbose

Specifies verbosity. Default: true.

In verbose mode prints executed commands with outputs of it. Same as set -x in bash.

__filename & __dirname

In ESM modules, Node.js does not provide __filename and __dirname globals. As such globals really handy in scripts, zx provides such globals, so they can be used in .mjs files (via using zx binary).

Importing from other scripts

It's possible to use $ and others with explicit import.

#!/usr/bin/env node
import {$} from 'zx'
await $`date`

Passing env variables

process.env.FOO = 'bar'
await $`echo $FOO`

Executing remote scripts

If arg to zx bin starts with https://, it will be downloaded and executed.

zx https://medv.io/example-script.mjs

License

Apache-2.0

Disclaimer: This is not an officially supported Google product.