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663 lines
19 KiB
663 lines
19 KiB
<img src="media/logo.svg" width="400"> |
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<br> |
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[![Coverage Status](https://codecov.io/gh/sindresorhus/execa/branch/main/graph/badge.svg)](https://codecov.io/gh/sindresorhus/execa) |
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> Process execution for humans |
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## Why |
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This package improves [`child_process`](https://nodejs.org/api/child_process.html) methods with: |
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- Promise interface. |
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- [Strips the final newline](#stripfinalnewline) from the output so you don't have to do `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. 100 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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- [Get interleaved output](#all) from `stdout` and `stderr` similar to what is printed on the terminal. [*(Async only)*](#execasyncfile-arguments-options) |
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- [Can specify file and arguments as a single string without a shell](#execacommandcommand-options) |
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- More descriptive errors. |
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## Install |
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``` |
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$ npm install 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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(async () => { |
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const {stdout} = await execa('echo', ['unicorns']); |
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console.log(stdout); |
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//=> 'unicorns' |
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})(); |
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``` |
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### Pipe the child process stdout to the parent |
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```js |
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const execa = require('execa'); |
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execa('echo', ['unicorns']).stdout.pipe(process.stdout); |
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``` |
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### Handling Errors |
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```js |
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const execa = require('execa'); |
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(async () => { |
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// Catching an error |
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try { |
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await execa('unknown', ['command']); |
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} catch (error) { |
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console.log(error); |
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/* |
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{ |
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message: 'Command failed with ENOENT: unknown command spawn unknown ENOENT', |
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errno: -2, |
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code: 'ENOENT', |
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syscall: 'spawn unknown', |
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path: 'unknown', |
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spawnargs: ['command'], |
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originalMessage: 'spawn unknown ENOENT', |
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shortMessage: 'Command failed with ENOENT: unknown command spawn unknown ENOENT', |
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command: 'unknown command', |
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escapedCommand: 'unknown command', |
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stdout: '', |
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stderr: '', |
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all: '', |
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failed: true, |
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timedOut: false, |
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isCanceled: false, |
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killed: false |
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} |
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*/ |
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} |
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})(); |
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``` |
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### Cancelling a spawned process |
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```js |
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const execa = require('execa'); |
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(async () => { |
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const subprocess = execa('node'); |
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setTimeout(() => { |
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subprocess.cancel(); |
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}, 1000); |
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try { |
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await subprocess; |
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} catch (error) { |
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console.log(subprocess.killed); // true |
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console.log(error.isCanceled); // true |
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} |
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})() |
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``` |
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### Catching an error with the sync method |
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```js |
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try { |
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execa.sync('unknown', ['command']); |
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} catch (error) { |
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console.log(error); |
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/* |
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{ |
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message: 'Command failed with ENOENT: unknown command spawnSync unknown ENOENT', |
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errno: -2, |
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code: 'ENOENT', |
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syscall: 'spawnSync unknown', |
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path: 'unknown', |
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spawnargs: ['command'], |
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originalMessage: 'spawnSync unknown ENOENT', |
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shortMessage: 'Command failed with ENOENT: unknown command spawnSync unknown ENOENT', |
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command: 'unknown command', |
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escapedCommand: 'unknown command', |
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stdout: '', |
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stderr: '', |
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all: '', |
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failed: true, |
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timedOut: false, |
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isCanceled: false, |
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killed: false |
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} |
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*/ |
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} |
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``` |
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### Kill a process |
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Using SIGTERM, and after 2 seconds, kill it with SIGKILL. |
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```js |
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const subprocess = execa('node'); |
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setTimeout(() => { |
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subprocess.kill('SIGTERM', { |
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forceKillAfterTimeout: 2000 |
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}); |
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}, 1000); |
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``` |
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## API |
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### execa(file, arguments, options?) |
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Execute a file. Think of this as a mix of [`child_process.execFile()`](https://nodejs.org/api/child_process.html#child_process_child_process_execfile_file_args_options_callback) and [`child_process.spawn()`](https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options). |
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No escaping/quoting is needed. |
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Unless the [`shell`](#shell) option is used, no shell interpreter (Bash, `cmd.exe`, etc.) is used, so shell features such as variables substitution (`echo $PATH`) are not allowed. |
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Returns a [`child_process` instance](https://nodejs.org/api/child_process.html#child_process_class_childprocess) which: |
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- is also a `Promise` resolving or rejecting with a [`childProcessResult`](#childProcessResult). |
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- exposes the following additional methods and properties. |
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#### kill(signal?, options?) |
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Same as the original [`child_process#kill()`](https://nodejs.org/api/child_process.html#child_process_subprocess_kill_signal) except: if `signal` is `SIGTERM` (the default value) and the child process is not terminated after 5 seconds, force it by sending `SIGKILL`. |
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##### options.forceKillAfterTimeout |
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Type: `number | false`\ |
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Default: `5000` |
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Milliseconds to wait for the child process to terminate before sending `SIGKILL`. |
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Can be disabled with `false`. |
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#### cancel() |
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Similar to [`childProcess.kill()`](https://nodejs.org/api/child_process.html#child_process_subprocess_kill_signal). This is preferred when cancelling the child process execution as the error is more descriptive and [`childProcessResult.isCanceled`](#iscanceled) is set to `true`. |
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#### all |
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Type: `ReadableStream | undefined` |
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Stream combining/interleaving [`stdout`](https://nodejs.org/api/child_process.html#child_process_subprocess_stdout) and [`stderr`](https://nodejs.org/api/child_process.html#child_process_subprocess_stderr). |
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This is `undefined` if either: |
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- the [`all` option](#all-2) is `false` (the default value) |
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- both [`stdout`](#stdout-1) and [`stderr`](#stderr-1) options are set to [`'inherit'`, `'ipc'`, `Stream` or `integer`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio) |
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### execa.sync(file, arguments?, options?) |
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Execute a file synchronously. |
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Returns or throws a [`childProcessResult`](#childProcessResult). |
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### execa.command(command, options?) |
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Same as [`execa()`](#execafile-arguments-options) except both file and arguments are specified in a single `command` string. For example, `execa('echo', ['unicorns'])` is the same as `execa.command('echo unicorns')`. |
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If the file or an argument contains spaces, they must be escaped with backslashes. This matters especially if `command` is not a constant but a variable, for example with `__dirname` or `process.cwd()`. Except for spaces, no escaping/quoting is needed. |
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The [`shell` option](#shell) must be used if the `command` uses shell-specific features (for example, `&&` or `||`), as opposed to being a simple `file` followed by its `arguments`. |
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### execa.commandSync(command, options?) |
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Same as [`execa.command()`](#execacommand-command-options) but synchronous. |
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Returns or throws a [`childProcessResult`](#childProcessResult). |
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### execa.node(scriptPath, arguments?, options?) |
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Execute a Node.js script as a child process. |
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Same as `execa('node', [scriptPath, ...arguments], options)` except (like [`child_process#fork()`](https://nodejs.org/api/child_process.html#child_process_child_process_fork_modulepath_args_options)): |
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- the current Node version and options are used. This can be overridden using the [`nodePath`](#nodepath-for-node-only) and [`nodeOptions`](#nodeoptions-for-node-only) options. |
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- the [`shell`](#shell) option cannot be used |
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- an extra channel [`ipc`](https://nodejs.org/api/child_process.html#child_process_options_stdio) is passed to [`stdio`](#stdio) |
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### childProcessResult |
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Type: `object` |
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Result of a child process execution. On success this is a plain object. On failure this is also an `Error` instance. |
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The child process [fails](#failed) when: |
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- its [exit code](#exitcode) is not `0` |
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- it was [killed](#killed) with a [signal](#signal) |
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- [timing out](#timedout) |
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- [being canceled](#iscanceled) |
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- there's not enough memory or there are already too many child processes |
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#### command |
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Type: `string` |
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The file and arguments that were run, for logging purposes. |
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This is not escaped and should not be executed directly as a process, including using [`execa()`](#execafile-arguments-options) or [`execa.command()`](#execacommandcommand-options). |
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#### escapedCommand |
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Type: `string` |
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Same as [`command`](#command) but escaped. |
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This is meant to be copy and pasted into a shell, for debugging purposes. |
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Since the escaping is fairly basic, this should not be executed directly as a process, including using [`execa()`](#execafile-arguments-options) or [`execa.command()`](#execacommandcommand-options). |
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#### exitCode |
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Type: `number` |
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The numeric exit code of the process that was run. |
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#### stdout |
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Type: `string | Buffer` |
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The output of the process on stdout. |
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#### stderr |
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Type: `string | Buffer` |
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The output of the process on stderr. |
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#### all |
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Type: `string | Buffer | undefined` |
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The output of the process with `stdout` and `stderr` interleaved. |
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This is `undefined` if either: |
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- the [`all` option](#all-2) is `false` (the default value) |
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- `execa.sync()` was used |
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#### failed |
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Type: `boolean` |
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Whether the process failed to run. |
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#### timedOut |
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Type: `boolean` |
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Whether the process timed out. |
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#### isCanceled |
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Type: `boolean` |
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Whether the process was canceled. |
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#### killed |
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Type: `boolean` |
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Whether the process was killed. |
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#### signal |
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Type: `string | undefined` |
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The name of the signal that was used to terminate the process. For example, `SIGFPE`. |
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If a signal terminated the process, this property is defined and included in the error message. Otherwise it is `undefined`. |
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#### signalDescription |
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Type: `string | undefined` |
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A human-friendly description of the signal that was used to terminate the process. For example, `Floating point arithmetic error`. |
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If a signal terminated the process, this property is defined and included in the error message. Otherwise it is `undefined`. It is also `undefined` when the signal is very uncommon which should seldomly happen. |
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#### message |
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Type: `string` |
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Error message when the child process failed to run. In addition to the [underlying error message](#originalMessage), it also contains some information related to why the child process errored. |
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The child process [stderr](#stderr) then [stdout](#stdout) are appended to the end, separated with newlines and not interleaved. |
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#### shortMessage |
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Type: `string` |
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This is the same as the [`message` property](#message) except it does not include the child process stdout/stderr. |
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#### originalMessage |
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Type: `string | undefined` |
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Original error message. This is the same as the `message` property except it includes neither the child process stdout/stderr nor some additional information added by Execa. |
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This is `undefined` unless the child process exited due to an `error` event or a timeout. |
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### options |
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Type: `object` |
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#### cleanup |
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Type: `boolean`\ |
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Default: `true` |
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Kill the spawned process when the parent process exits unless either: |
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- the spawned process is [`detached`](https://nodejs.org/api/child_process.html#child_process_options_detached) |
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- the parent process is terminated abruptly, for example, with `SIGKILL` as opposed to `SIGTERM` or a normal exit |
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#### preferLocal |
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Type: `boolean`\ |
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Default: `false` |
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Prefer locally installed binaries when looking for a binary to execute.\ |
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If you `$ npm install foo`, you can then `execa('foo')`. |
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#### localDir |
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Type: `string`\ |
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Default: `process.cwd()` |
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Preferred path to find locally installed binaries in (use with `preferLocal`). |
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#### execPath |
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Type: `string`\ |
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Default: `process.execPath` (Current Node.js executable) |
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Path to the Node.js executable to use in child processes. |
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This can be either an absolute path or a path relative to the [`cwd` option](#cwd). |
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Requires [`preferLocal`](#preferlocal) to be `true`. |
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For example, this can be used together with [`get-node`](https://github.com/ehmicky/get-node) to run a specific Node.js version in a child process. |
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#### buffer |
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Type: `boolean`\ |
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Default: `true` |
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Buffer the output from the spawned process. When set to `false`, you must read the output of [`stdout`](#stdout-1) and [`stderr`](#stderr-1) (or [`all`](#all) if the [`all`](#all-2) option is `true`). Otherwise the returned promise will not be resolved/rejected. |
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If the spawned process fails, [`error.stdout`](#stdout), [`error.stderr`](#stderr), and [`error.all`](#all) will contain the buffered data. |
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#### input |
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Type: `string | Buffer | stream.Readable` |
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Write some input to the `stdin` of your binary.\ |
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Streams are not allowed when using the synchronous methods. |
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#### stdin |
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Type: `string | number | Stream | undefined`\ |
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Default: `pipe` |
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Same options as [`stdio`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio). |
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#### stdout |
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Type: `string | number | Stream | undefined`\ |
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Default: `pipe` |
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Same options as [`stdio`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio). |
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#### stderr |
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Type: `string | number | Stream | undefined`\ |
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Default: `pipe` |
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Same options as [`stdio`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio). |
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#### all |
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Type: `boolean`\ |
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Default: `false` |
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Add an `.all` property on the [promise](#all) and the [resolved value](#all-1). The property contains the output of the process with `stdout` and `stderr` interleaved. |
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#### reject |
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Type: `boolean`\ |
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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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#### stripFinalNewline |
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Type: `boolean`\ |
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Default: `true` |
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Strip the final [newline character](https://en.wikipedia.org/wiki/Newline) from the output. |
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#### extendEnv |
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Type: `boolean`\ |
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Default: `true` |
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Set to `false` if you don't want to extend the environment variables when providing the `env` property. |
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--- |
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Execa also accepts the below options which are the same as the options for [`child_process#spawn()`](https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options)/[`child_process#exec()`](https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback) |
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#### cwd |
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Type: `string`\ |
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Default: `process.cwd()` |
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Current working directory of the child process. |
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#### env |
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Type: `object`\ |
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Default: `process.env` |
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Environment key-value pairs. Extends automatically from `process.env`. Set [`extendEnv`](#extendenv) to `false` if you don't want this. |
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#### argv0 |
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Type: `string` |
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Explicitly set the value of `argv[0]` sent to the child process. This will be set to `file` if not specified. |
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#### stdio |
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Type: `string | string[]`\ |
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Default: `pipe` |
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Child's [stdio](https://nodejs.org/api/child_process.html#child_process_options_stdio) configuration. |
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#### serialization |
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Type: `string`\ |
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Default: `'json'` |
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Specify the kind of serialization used for sending messages between processes when using the [`stdio: 'ipc'`](#stdio) option or [`execa.node()`](#execanodescriptpath-arguments-options): |
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- `json`: Uses `JSON.stringify()` and `JSON.parse()`. |
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- `advanced`: Uses [`v8.serialize()`](https://nodejs.org/api/v8.html#v8_v8_serialize_value) |
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Requires Node.js `13.2.0` or later. |
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[More info.](https://nodejs.org/api/child_process.html#child_process_advanced_serialization) |
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#### detached |
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Type: `boolean` |
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Prepare child to run independently of its parent process. Specific behavior [depends on the platform](https://nodejs.org/api/child_process.html#child_process_options_detached). |
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#### uid |
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Type: `number` |
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Sets the user identity of the process. |
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#### gid |
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Type: `number` |
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Sets the group identity of the process. |
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#### shell |
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Type: `boolean | string`\ |
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Default: `false` |
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If `true`, runs `file` inside of a shell. Uses `/bin/sh` on UNIX and `cmd.exe` on Windows. A different shell can be specified as a string. The shell should understand the `-c` switch on UNIX or `/d /s /c` on Windows. |
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We recommend against using this option since it is: |
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- not cross-platform, encouraging shell-specific syntax. |
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- slower, because of the additional shell interpretation. |
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- unsafe, potentially allowing command injection. |
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#### encoding |
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Type: `string | null`\ |
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Default: `utf8` |
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Specify the character encoding used to decode the `stdout` and `stderr` output. If set to `null`, then `stdout` and `stderr` will be a `Buffer` instead of a string. |
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#### timeout |
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Type: `number`\ |
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Default: `0` |
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If timeout is greater than `0`, the parent will send the signal identified by the `killSignal` property (the default is `SIGTERM`) if the child runs longer than timeout milliseconds. |
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#### maxBuffer |
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Type: `number`\ |
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Default: `100_000_000` (100 MB) |
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Largest amount of data in bytes allowed on `stdout` or `stderr`. |
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#### killSignal |
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Type: `string | number`\ |
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Default: `SIGTERM` |
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Signal value to be used when the spawned process will be killed. |
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#### windowsVerbatimArguments |
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Type: `boolean`\ |
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Default: `false` |
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If `true`, no quoting or escaping of arguments is done on Windows. Ignored on other platforms. This is set to `true` automatically when the `shell` option is `true`. |
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#### windowsHide |
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Type: `boolean`\ |
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Default: `true` |
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On Windows, do not create a new console window. Please note this also prevents `CTRL-C` [from working](https://github.com/nodejs/node/issues/29837) on Windows. |
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#### nodePath *(For `.node()` only)* |
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Type: `string`\ |
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Default: [`process.execPath`](https://nodejs.org/api/process.html#process_process_execpath) |
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Node.js executable used to create the child process. |
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#### nodeOptions *(For `.node()` only)* |
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Type: `string[]`\ |
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Default: [`process.execArgv`](https://nodejs.org/api/process.html#process_process_execargv) |
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List of [CLI options](https://nodejs.org/api/cli.html#cli_options) passed to the Node.js executable. |
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## Tips |
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### Retry on error |
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Gracefully handle failures by using automatic retries and exponential backoff with the [`p-retry`](https://github.com/sindresorhus/p-retry) package: |
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```js |
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const pRetry = require('p-retry'); |
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const run = async () => { |
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const results = await execa('curl', ['-sSL', 'https://sindresorhus.com/unicorn']); |
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return results; |
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}; |
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|
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(async () => { |
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console.log(await pRetry(run, {retries: 5})); |
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})(); |
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``` |
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|
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### Save and pipe output from a child process |
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|
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Let's say you want to show the output of a child process in real-time while also saving it to a variable. |
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|
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```js |
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const execa = require('execa'); |
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|
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const subprocess = execa('echo', ['foo']); |
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subprocess.stdout.pipe(process.stdout); |
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|
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(async () => { |
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const {stdout} = await subprocess; |
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console.log('child output:', stdout); |
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})(); |
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``` |
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|
|
### Redirect output to a file |
|
|
|
```js |
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const execa = require('execa'); |
|
|
|
const subprocess = execa('echo', ['foo']) |
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subprocess.stdout.pipe(fs.createWriteStream('stdout.txt')) |
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``` |
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|
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### Redirect input from a file |
|
|
|
```js |
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const execa = require('execa'); |
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|
|
const subprocess = execa('cat') |
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fs.createReadStream('stdin.txt').pipe(subprocess.stdin) |
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``` |
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|
|
### Execute the current package's binary |
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|
|
```js |
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const {getBinPathSync} = require('get-bin-path'); |
|
|
|
const binPath = getBinPathSync(); |
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const subprocess = execa(binPath); |
|
``` |
|
|
|
`execa` can be combined with [`get-bin-path`](https://github.com/ehmicky/get-bin-path) to test the current package's binary. As opposed to hard-coding the path to the binary, this validates that the `package.json` `bin` field is correctly set up. |
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|
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## Related |
|
|
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- [gulp-execa](https://github.com/ehmicky/gulp-execa) - Gulp plugin for `execa` |
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- [nvexeca](https://github.com/ehmicky/nvexeca) - Run `execa` using any Node.js version |
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- [sudo-prompt](https://github.com/jorangreef/sudo-prompt) - Run commands with elevated privileges. |
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|
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## Maintainers |
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|
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- [Sindre Sorhus](https://github.com/sindresorhus) |
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- [@ehmicky](https://github.com/ehmicky) |
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|
|
--- |
|
|
|
<div align="center"> |
|
<b> |
|
<a href="https://tidelift.com/subscription/pkg/npm-execa?utm_source=npm-execa&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a> |
|
</b> |
|
<br> |
|
<sub> |
|
Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies. |
|
</sub> |
|
</div>
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|