151 lines
4.6 KiB
Markdown
151 lines
4.6 KiB
Markdown
# execa [](https://travis-ci.org/sindresorhus/execa) [](https://ci.appveyor.com/project/sindresorhus/execa/branch/master) [](https://coveralls.io/github/sindresorhus/execa?branch=master)
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> A better [`child_process`](https://nodejs.org/api/child_process.html)
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## Why
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- Promise interface.
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- [Strips EOF](https://github.com/sindresorhus/strip-eof) from the output so you don't have to `stdout.trim()`.
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- Supports [shebang](https://en.wikipedia.org/wiki/Shebang_(Unix)) binaries cross-platform.
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- [Improved Windows support.](https://github.com/IndigoUnited/node-cross-spawn#why)
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- Higher max buffer. 10 MB instead of 200 KB.
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- [Executes locally installed binaries by name.](#preferlocal)
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- [Cleans up spawned processes when the parent process dies.](#cleanup)
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## Install
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```
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$ npm install --save execa
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```
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## Usage
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```js
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const execa = require('execa');
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execa('echo', ['unicorns']).then(result => {
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console.log(result.stdout);
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//=> 'unicorns'
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});
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// pipe the child process stdout to the current stdout
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execa('echo', ['unicorns']).stdout.pipe(process.stdout);
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execa.shell('echo unicorns').then(result => {
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console.log(result.stdout);
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//=> 'unicorns'
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});
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// example of catching an error
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execa.shell('exit 3').catch(error => {
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console.log(error);
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/*
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{
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message: 'Command failed: /bin/sh -c exit 3'
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killed: false,
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code: 3,
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signal: null,
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cmd: '/bin/sh -c exit 3',
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stdout: '',
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stderr: '',
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timedOut: false
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}
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*/
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});
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```
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## API
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### execa(file, [arguments], [options])
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Execute a file.
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Same options as [`child_process.execFile`](https://nodejs.org/api/child_process.html#child_process_child_process_execfile_file_args_options_callback).
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Think of this as a mix of `child_process.execFile` and `child_process.spawn`.
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Returns a [`child_process` instance](https://nodejs.org/api/child_process.html#child_process_class_childprocess), which is enhanced to also be a `Promise` for a result `Object` with `stdout` and `stderr` properties.
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### execa.stdout(file, [arguments], [options])
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Same as `execa()`, but returns only `stdout`.
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### execa.stderr(file, [arguments], [options])
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Same as `execa()`, but returns only `stderr`.
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### execa.shell(command, [options])
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Execute a command through the system shell. Prefer `execa()` whenever possible, as it's both faster and safer.
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Same options as [`child_process.exec`](https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback).
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Returns a [`child_process` instance](https://nodejs.org/api/child_process.html#child_process_class_childprocess).
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The `child_process` instance is enhanced to also be promise for a result object with `stdout` and `stderr` properties.
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### execa.sync(file, [arguments], [options])
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Execute a file synchronously.
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Same options as [`child_process.execFileSync`](https://nodejs.org/api/child_process.html#child_process_child_process_execfilesync_file_args_options), except the default encoding is `utf8` instead of `buffer`.
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Returns the same result object as [`child_process.spawnSync`](https://nodejs.org/api/child_process.html#child_process_child_process_spawnsync_command_args_options).
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### execa.shellSync(file, [options])
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Execute a command synchronously through the system shell.
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Same options as [`child_process.execSync`](https://nodejs.org/api/child_process.html#child_process_child_process_execsync_command_options), except the default encoding is `utf8` instead of `buffer`.
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Returns the same result object as [`child_process.spawnSync`](https://nodejs.org/api/child_process.html#child_process_child_process_spawnsync_command_args_options).
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### options
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Additional options:
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#### stripEof
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Type: `boolean`<br>
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Default: `true`
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[Strip EOF](https://github.com/sindresorhus/strip-eof) (last newline) from the output.
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#### preferLocal
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Type: `boolean`<br>
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Default: `true`
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Prefer locally installed binaries when looking for a binary to execute.<br>
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If you `$ npm install foo`, you can then `execa('foo')`.
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#### input
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Type: `string` `Buffer` `ReadableStream`
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Write some input to the `stdin` of your binary.<br>
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Streams are not allowed when using the synchronous methods.
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#### reject
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Type: `boolean`<br>
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Default: `true`
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Setting this to `false` resolves the promise with the error instead of rejecting it.
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#### cleanup
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Type: `boolean`<br>
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Default: `true`
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Keep track of the spawned process and `kill` it when the parent process exits.
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## License
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MIT © [Sindre Sorhus](https://sindresorhus.com)
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