🐚 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. The 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 the .js extension,
wrap your scripts in something like void async function () {...}().
Add the following shebang to the beginning of your zx scripts:
#!/usr/bin/env zx
Now you will be able to run your script like so:
chmod +x ./script.mjs
./script.mjs
Or via the zx executable:
zx ./script.mjs
When using zx via the executable or a shebang, all of the functions
($, cd, fetch, etc) are available straight away without any imports.
$`command`
Executes a given string using the exec function from the
child_process package and returns ProcessPromise<ProcessOutput>.
let count = parseInt(await $`ls -1 | wc -l`)
console.log(`Files count: ${count}`)
For example, to upload files in parallel:
let hosts = [...]
await Promise.all(hosts.map(host =>
$`rsync -azP ./src ${host}:/var/www`
))
If the executed program returns a 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}`)
}
ProcessPromise
class ProcessPromise<T> extends Promise<T> {
readonly stdin: Writable
readonly stdout: Readable
readonly stderr: Readable
pipe(dest): ProcessPromise<T>
}
The pipe() method can be used to redirect stdout:
await $`cat file.txt`.pipe(process.stdout)
Read more about pipelines.
ProcessOutput
class ProcessOutput {
readonly exitCode: number
readonly stdout: string
readonly stderr: string
toString(): string
}
cd()
Changes the current working directory.
cd('/tmp')
await $`pwd` // outputs /tmp
fetch()
A wrapper around the node-fetch package.
let resp = await fetch('http://wttr.in')
if (resp.ok) {
console.log(await resp.text())
}
question()
A wrapper around the readline package.
Usage:
let bear = await question('What kind of bear is best? ')
let token = await question('Choose env variable: ', {
choices: Object.keys(process.env)
})
In second argument, array of choices for Tab autocompletion can be specified.
function question(query?: string, options?: QuestionOptions): Promise<string>
type QuestionOptions = { choices: string[] }
sleep()
A wrapper around the setTimeout function.
function sleep(ms: number): Promise<void>
Usage:
await sleep(1000)
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. It is asynchronous by default.
let content = await fs.readFile('./package.json')
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 the command what will be prefixed to all commands run.
Default is set -euo pipefail;.
$.quote
Specifies a function what will be used for escaping special characters during
command substitution.
Default is the shq package.
$.verbose
Specifies verbosity. Default is true.
In verbose mode, the zx prints all executed commands alongside with their
outputs.
__filename & __dirname
In ESM modules, Node.js does not provide
__filename and __dirname globals. As such globals are really handy in scripts,
zx provides these for use in .mjs files (when using the zx executable).
require()
In ESM
modules, the require() function is not defined.
The zx provides require() function, so it can be used with imports in .mjs
files (when using zx executable).
let {version} = require('./package.json')
Passing env variables
process.env.FOO = 'bar'
await $`echo $FOO`
Passing array of values
If array of values passed as argument to $, items of the array will be escaped
individually and concatenated via space.
Example:
let files = [...]
await $`tar cz ${files}`
Importing from other scripts
It is possible to make use of $ and other functions via explicit imports:
#!/usr/bin/env node
import {$} from 'zx'
await $`date`
Scripts without extensions
If script does not have a file extension (like .git/hooks/pre-commit), zx
assumes what it is a ESM
module.
Markdown scripts
The zx can execute scripts written in markdown
(examples/index.md):
zx examples/index.md
Executing remote scripts
If the argument to the zx executable starts with https://, the file 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.
