import type {Options} from '../arguments/options.js';
import type {ResultPromise} from '../subprocess/subprocess.js';
import type {TemplateString} from './template.js';
/**
Executes a command using `file ...arguments`.
When `command` is a template string, it includes both the `file` and its `arguments`.
`execa(options)` can be used to return a new instance of this method but with different default `options`. Consecutive calls are merged to previous ones.
@param file - The program/script to execute, as a string or file URL
@param arguments - Arguments to pass to `file` on execution.
@returns A `ResultPromise` that is both:
- the subprocess.
- a `Promise` either resolving with its successful `result`, or rejecting with its `error`.
@throws `ExecaError`
@example
Simple syntax
```
import {execa} from 'execa';
const {stdout} = await execa`npm run build`;
// Print command's output
console.log(stdout);
```
@example Script
```
import {$} from 'execa';
const {stdout: name} = await $`cat package.json`.pipe`grep name`;
console.log(name);
const branch = await $`git branch --show-current`;
await $`dep deploy --branch=${branch}`;
await Promise.all([
$`sleep 1`,
$`sleep 2`,
$`sleep 3`,
]);
const directoryName = 'foo bar';
await $`mkdir /tmp/${directoryName}`;
```
@example Local binaries
```
$ npm install -D eslint
```
```
await execa({preferLocal: true})`eslint`;
```
@example Pipe multiple subprocesses
```
const {stdout, pipedFrom} = await execa`npm run build`
.pipe`sort`
.pipe`head -n 2`;
// Output of `npm run build | sort | head -n 2`
console.log(stdout);
// Output of `npm run build | sort`
console.log(pipedFrom[0].stdout);
// Output of `npm run build`
console.log(pipedFrom[0].pipedFrom[0].stdout);
```
@example Interleaved output
```
const {all} = await execa({all: true})`npm run build`;
// stdout + stderr, interleaved
console.log(all);
```
@example Programmatic + terminal output
```
const {stdout} = await execa({stdout: ['pipe', 'inherit']})`npm run build`;
// stdout is also printed to the terminal
console.log(stdout);
```
@example Simple input
```
const getInputString = () => { /* ... *\/ };
const {stdout} = await execa({input: getInputString()})`sort`;
console.log(stdout);
```
@example File input
```
// Similar to: npm run build < input.txt
await execa({stdin: {file: 'input.txt'}})`npm run build`;
```
@example File output
```
// Similar to: npm run build > output.txt
await execa({stdout: {file: 'output.txt'}})`npm run build`;
```
@example Split into text lines
```
const {stdout} = await execa({lines: true})`npm run build`;
// Print first 10 lines
console.log(stdout.slice(0, 10).join('\n'));
```
@example Iterate over text lines
```
for await (const line of execa`npm run build`) {
if (line.includes('WARN')) {
console.warn(line);
}
}
```
@example Transform/filter output
```
let count = 0;
// Filter out secret lines, then prepend the line number
const transform = function * (line) {
if (!line.includes('secret')) {
yield `[${count++}] ${line}`;
}
};
await execa({stdout: transform})`npm run build`;
```
@example Web streams
```
const response = await fetch('https://example.com');
await execa({stdin: response.body})`sort`;
```
@example Convert to Duplex stream
```
import {execa} from 'execa';
import {pipeline} from 'node:stream/promises';
import {createReadStream, createWriteStream} from 'node:fs';
await pipeline(
createReadStream('./input.txt'),
execa`node ./transform.js`.duplex(),
createWriteStream('./output.txt'),
);
```
@example Exchange messages
```
// parent.js
import {execaNode} from 'execa';
const subprocess = execaNode`child.js`;
await subprocess.sendMessage('Hello from parent');
const message = await subprocess.getOneMessage();
console.log(message); // 'Hello from child'
```
```
// child.js
import {getOneMessage, sendMessage} from 'execa';
const message = await getOneMessage(); // 'Hello from parent'
const newMessage = message.replace('parent', 'child'); // 'Hello from child'
await sendMessage(newMessage);
```
@example Any input type
```
// main.js
import {execaNode} from 'execa';
const ipcInput = [
{task: 'lint', ignore: /test\.js/},
{task: 'copy', files: new Set(['main.js', 'index.js']),
}];
await execaNode({ipcInput})`build.js`;
```
```
// build.js
import {getOneMessage} from 'execa';
const ipcInput = await getOneMessage();
```
@example Any output type
```
// main.js
import {execaNode} from 'execa';
const {ipcOutput} = await execaNode`build.js`;
console.log(ipcOutput[0]); // {kind: 'start', timestamp: date}
console.log(ipcOutput[1]); // {kind: 'stop', timestamp: date}
```
```
// build.js
import {sendMessage} from 'execa';
const runBuild = () => { /* ... *\/ };
await sendMessage({kind: 'start', timestamp: new Date()});
await runBuild();
await sendMessage({kind: 'stop', timestamp: new Date()});
```
@example Graceful termination
```
// main.js
import {execaNode} from 'execa';
const controller = new AbortController();
setTimeout(() => {
controller.abort();
}, 5000);
await execaNode({
cancelSignal: controller.signal,
gracefulCancel: true,
})`build.js`;
```
```
// build.js
import {getCancelSignal} from 'execa';
const cancelSignal = await getCancelSignal();
const url = 'https://example.com/build/info';
const response = await fetch(url, {signal: cancelSignal});
```
@example Detailed error
```
import {execa, ExecaError} from 'execa';
try {
await execa`unknown command`;
} catch (error) {
if (error instanceof ExecaError) {
console.log(error);
}
/*
ExecaError: Command failed with ENOENT: unknown command
spawn unknown ENOENT
at ...
at ... {
shortMessage: 'Command failed with ENOENT: unknown command\nspawn unknown ENOENT',
originalMessage: 'spawn unknown ENOENT',
command: 'unknown command',
escapedCommand: 'unknown command',
cwd: '/path/to/cwd',
durationMs: 28.217566,
failed: true,
timedOut: false,
isCanceled: false,
isTerminated: false,
isMaxBuffer: false,
code: 'ENOENT',
stdout: '',
stderr: '',
stdio: [undefined, '', ''],
pipedFrom: []
[cause]: Error: spawn unknown ENOENT
at ...
at ... {
errno: -2,
code: 'ENOENT',
syscall: 'spawn unknown',
path: 'unknown',
spawnargs: [ 'command' ]
}
}
*\/
}
```
@example Verbose mode
```
await execa`npm run build`;
await execa`npm run test`;
```
```
$ NODE_DEBUG=execa node build.js
[00:57:44.581] [0] $ npm run build
[00:57:44.653] [0] Building application...
[00:57:44.653] [0] Done building.
[00:57:44.658] [0] ✔ (done in 78ms)
[00:57:44.658] [1] $ npm run test
[00:57:44.740] [1] Running tests...
[00:57:44.740] [1] Error: the entrypoint is invalid.
[00:57:44.747] [1] ✘ Command failed with exit code 1: npm run test
[00:57:44.747] [1] ✘ (done in 89ms)
```
@example Custom logging
```
import {execa as execa_} from 'execa';
import {createLogger, transports} from 'winston';
// Log to a file using Winston
const transport = new transports.File({filename: 'logs.txt'});
const logger = createLogger({transports: [transport]});
const LOG_LEVELS = {
command: 'info',
output: 'verbose',
ipc: 'verbose',
error: 'error',
duration: 'info',
};
const execa = execa_({
verbose(verboseLine, {message, ...verboseObject}) {
const level = LOG_LEVELS[verboseObject.type];
logger[level](message, verboseObject);
},
});
await execa`npm run build`;
await execa`npm run test`;
```
*/
export declare const execa: ExecaMethod<{}>;
/**
`execa()` method either exported by Execa, or bound using `execa(options)`.
*/
export type ExecaMethod =
& ExecaBind
& ExecaTemplate
& ExecaArrayLong
& ExecaArrayShort;
// `execa(options)` binding
type ExecaBind =
(options: NewOptionsType)
=> ExecaMethod;
// `execa`command`` template syntax
type ExecaTemplate =
(...templateString: TemplateString)
=> ResultPromise;
// `execa('file', ['argument'], {})` array syntax
type ExecaArrayLong =
(file: string | URL, arguments?: readonly string[], options?: NewOptionsType)
=> ResultPromise;
// `execa('file', {})` array syntax
type ExecaArrayShort =
(file: string | URL, options?: NewOptionsType)
=> ResultPromise;