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JSON</a> </li> <li class="version-picker"> <a href="#">View another version <span>▼</span></a> <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v12.x/api/child_process.html">12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v11.x/api/child_process.html">11.x</a></li> <li><a href="https://nodejs.org/docs/latest-v10.x/api/child_process.html">10.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v9.x/api/child_process.html">9.x</a></li> <li><a href="https://nodejs.org/docs/latest-v8.x/api/child_process.html">8.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v7.x/api/child_process.html">7.x</a></li> <li><a href="https://nodejs.org/docs/latest-v6.x/api/child_process.html">6.x</a></li> <li><a href="https://nodejs.org/docs/latest-v5.x/api/child_process.html">5.x</a></li> <li><a href="https://nodejs.org/docs/latest-v4.x/api/child_process.html">4.x</a></li> <li><a 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href="#child_process_asynchronous_process_creation">Asynchronous Process Creation</a></p> <ul> <li><a href="#child_process_spawning_bat_and_cmd_files_on_windows">Spawning <code>.bat</code> and <code>.cmd</code> files on Windows</a></li> <li><a href="#child_process_child_process_exec_command_options_callback">child_process.exec(command[, options][, callback])</a></li> <li><a href="#child_process_child_process_execfile_file_args_options_callback">child_process.execFile(file[, args][, options][, callback])</a></li> <li><a href="#child_process_child_process_fork_modulepath_args_options">child_process.fork(modulePath[, args][, options])</a></li> <li> <p><a href="#child_process_child_process_spawn_command_args_options">child_process.spawn(command[, args][, options])</a></p> <ul> <li><a href="#child_process_options_detached">options.detached</a></li> <li><a href="#child_process_options_stdio">options.stdio</a></li> </ul> </li> </ul> </li> <li> <p><a href="#child_process_synchronous_process_creation">Synchronous Process Creation</a></p> <ul> <li><a href="#child_process_child_process_execfilesync_file_args_options">child_process.execFileSync(file[, args][, options])</a></li> <li><a href="#child_process_child_process_execsync_command_options">child_process.execSync(command[, options])</a></li> <li><a href="#child_process_child_process_spawnsync_command_args_options">child_process.spawnSync(command[, args][, options])</a></li> </ul> </li> <li> <p><a href="#child_process_class_childprocess">Class: ChildProcess</a></p> <ul> <li><a href="#child_process_event_close">Event: 'close'</a></li> <li><a href="#child_process_event_disconnect">Event: 'disconnect'</a></li> <li><a href="#child_process_event_error">Event: 'error'</a></li> <li><a href="#child_process_event_exit">Event: 'exit'</a></li> <li><a href="#child_process_event_message">Event: 'message'</a></li> <li><a href="#child_process_subprocess_channel">subprocess.channel</a></li> <li><a href="#child_process_subprocess_connected">subprocess.connected</a></li> <li><a href="#child_process_subprocess_disconnect">subprocess.disconnect()</a></li> <li><a href="#child_process_subprocess_kill_signal">subprocess.kill([signal])</a></li> <li><a href="#child_process_subprocess_killed">subprocess.killed</a></li> <li><a href="#child_process_subprocess_pid">subprocess.pid</a></li> <li><a href="#child_process_subprocess_ref">subprocess.ref()</a></li> <li> <p><a href="#child_process_subprocess_send_message_sendhandle_options_callback">subprocess.send(message[, sendHandle[, options]][, callback])</a></p> <ul> <li><a href="#child_process_example_sending_a_server_object">Example: sending a server object</a></li> <li><a href="#child_process_example_sending_a_socket_object">Example: sending a socket object</a></li> </ul> </li> <li><a href="#child_process_subprocess_stderr">subprocess.stderr</a></li> <li><a href="#child_process_subprocess_stdin">subprocess.stdin</a></li> <li><a href="#child_process_subprocess_stdio">subprocess.stdio</a></li> <li><a href="#child_process_subprocess_stdout">subprocess.stdout</a></li> <li><a href="#child_process_subprocess_unref">subprocess.unref()</a></li> </ul> </li> <li><a href="#child_process_maxbuffer_and_unicode"><code>maxBuffer</code> and Unicode</a></li> <li><a href="#child_process_shell_requirements">Shell Requirements</a></li> <li><a href="#child_process_default_windows_shell">Default Windows Shell</a></li> </ul> </li> </ul> </div> <div id="apicontent"> <h1>Child Process<span><a class="mark" href="#child_process_child_process" id="child_process_child_process">#</a></span></h1> <p></p><div class="api_stability api_stability_2"><a href="https://nodejs.org/api/documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> <p>The <code>child_process</code> module provides the ability to spawn child processes in a manner that is similar, but not identical, to <a href="http://man7.org/linux/man-pages/man3/popen.3.html"><code>popen(3)</code></a>. This capability is primarily provided by the <a href="#child_process_child_process_spawn_command_args_options"><code>child_process.spawn()</code></a> function:</p> <pre><code class="language-js">const { spawn } = require('child_process'); const ls = spawn('ls', ['-lh', '/usr']); ls.stdout.on('data', (data) => { console.log(`stdout: ${data}`); }); ls.stderr.on('data', (data) => { console.error(`stderr: ${data}`); }); ls.on('close', (code) => { console.log(`child process exited with code ${code}`); }); </code></pre> <p>By default, pipes for <code>stdin</code>, <code>stdout</code>, and <code>stderr</code> are established between the parent Node.js process and the spawned child. These pipes have limited (and platform-specific) capacity. If the child process writes to stdout in excess of that limit without the output being captured, the child process will block waiting for the pipe buffer to accept more data. This is identical to the behavior of pipes in the shell. Use the <code>{ stdio: 'ignore' }</code> option if the output will not be consumed.</p> <p>The <a href="#child_process_child_process_spawn_command_args_options"><code>child_process.spawn()</code></a> method spawns the child process asynchronously, without blocking the Node.js event loop. The <a href="#child_process_child_process_spawnsync_command_args_options"><code>child_process.spawnSync()</code></a> function provides equivalent functionality in a synchronous manner that blocks the event loop until the spawned process either exits or is terminated.</p> <p>For convenience, the <code>child_process</code> module provides a handful of synchronous and asynchronous alternatives to <a href="#child_process_child_process_spawn_command_args_options"><code>child_process.spawn()</code></a> and <a href="#child_process_child_process_spawnsync_command_args_options"><code>child_process.spawnSync()</code></a>. Each of these alternatives are implemented on top of <a href="#child_process_child_process_spawn_command_args_options"><code>child_process.spawn()</code></a> or <a href="#child_process_child_process_spawnsync_command_args_options"><code>child_process.spawnSync()</code></a>.</p> <ul> <li><a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a>: spawns a shell and runs a command within that shell, passing the <code>stdout</code> and <code>stderr</code> to a callback function when complete.</li> <li><a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a>: similar to <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a> except that it spawns the command directly without first spawning a shell by default.</li> <li><a href="#child_process_child_process_fork_modulepath_args_options"><code>child_process.fork()</code></a>: spawns a new Node.js process and invokes a specified module with an IPC communication channel established that allows sending messages between parent and child.</li> <li><a href="#child_process_child_process_execsync_command_options"><code>child_process.execSync()</code></a>: a synchronous version of <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a> that will block the Node.js event loop.</li> <li><a href="#child_process_child_process_execfilesync_file_args_options"><code>child_process.execFileSync()</code></a>: a synchronous version of <a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a> that will block the Node.js event loop.</li> </ul> <p>For certain use cases, such as automating shell scripts, the <a href="#child_process_synchronous_process_creation">synchronous counterparts</a> may be more convenient. In many cases, however, the synchronous methods can have significant impact on performance due to stalling the event loop while spawned processes complete.</p> <h2>Asynchronous Process Creation<span><a class="mark" href="#child_process_asynchronous_process_creation" id="child_process_asynchronous_process_creation">#</a></span></h2> <p>The <a href="#child_process_child_process_spawn_command_args_options"><code>child_process.spawn()</code></a>, <a href="#child_process_child_process_fork_modulepath_args_options"><code>child_process.fork()</code></a>, <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a>, and <a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a> methods all follow the idiomatic asynchronous programming pattern typical of other Node.js APIs.</p> <p>Each of the methods returns a <a href="#child_process_child_process"><code>ChildProcess</code></a> instance. These objects implement the Node.js <a href="https://nodejs.org/api/events.html#events_class_eventemitter"><code>EventEmitter</code></a> API, allowing the parent process to register listener functions that are called when certain events occur during the life cycle of the child process.</p> <p>The <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a> and <a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a> methods additionally allow for an optional <code>callback</code> function to be specified that is invoked when the child process terminates.</p> <h3>Spawning <code>.bat</code> and <code>.cmd</code> files on Windows<span><a class="mark" href="#child_process_spawning_bat_and_cmd_files_on_windows" id="child_process_spawning_bat_and_cmd_files_on_windows">#</a></span></h3> <p>The importance of the distinction between <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a> and <a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a> can vary based on platform. On Unix-type operating systems (Unix, Linux, macOS) <a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a> can be more efficient because it does not spawn a shell by default. On Windows, however, <code>.bat</code> and <code>.cmd</code> files are not executable on their own without a terminal, and therefore cannot be launched using <a href="#child_process_child_process_execfile_file_args_options_callback"><code>child_process.execFile()</code></a>. When running on Windows, <code>.bat</code> and <code>.cmd</code> files can be invoked using <a href="#child_process_child_process_spawn_command_args_options"><code>child_process.spawn()</code></a> with the <code>shell</code> option set, with <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a>, or by spawning <code>cmd.exe</code> and passing the <code>.bat</code> or <code>.cmd</code> file as an argument (which is what the <code>shell</code> option and <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a> do). In any case, if the script filename contains spaces it needs to be quoted.</p> <pre><code class="language-js">// On Windows Only... const { spawn } = require('child_process'); const bat = spawn('cmd.exe', ['/c', 'my.bat']); bat.stdout.on('data', (data) => { console.log(data.toString()); }); bat.stderr.on('data', (data) => { console.error(data.toString()); }); bat.on('exit', (code) => { console.log(`Child exited with code ${code}`); }); </code></pre> <pre><code class="language-js">// OR... const { exec } = require('child_process'); exec('my.bat', (err, stdout, stderr) => { if (err) { console.error(err); return; } console.log(stdout); }); // Script with spaces in the filename: const bat = spawn('"my script.cmd"', ['a', 'b'], { shell: true }); // or: exec('"my script.cmd" a b', (err, stdout, stderr) => { // ... }); </code></pre> <h3>child_process.exec(command[, options][, callback])<a class="srclink" href="https://github.com/nodejs/node/blob/3a2e75d9a5c31d20e429d505b82dd182e33f459a/lib/child_process.js#L143">[src]</a><span><a class="mark" href="#child_process_child_process_exec_command_options_callback" id="child_process_child_process_exec_command_options_callback">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.8.0</td> <td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> <tr><td>v0.1.90</td> <td><p><span>Added in: v0.1.90</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>command</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The command to run, with space-separated arguments.</li> <li> <p><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></p> <ul> <li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Current working directory of the child process. <strong>Default:</strong> <code>null</code>.</li> <li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'utf8'</code></li> <li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Shell to execute the command with. See <a href="#child_process_shell_requirements">Shell Requirements</a> and <a href="#child_process_default_windows_shell">Default Windows Shell</a>. <strong>Default:</strong> <code>'/bin/sh'</code> on Unix, <code>process.env.ComSpec</code> on Windows.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> <strong>Default:</strong> <code>0</code></li> <li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at <a href="#child_process_maxbuffer_and_unicode"><code>maxBuffer</code> and Unicode</a>. <strong>Default:</strong> <code>1024 * 1024</code>.</li> <li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>'SIGTERM'</code></li> <li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> <li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> <li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would normally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> </ul> </li> <li> <p><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> called with the output when process terminates.</p> <ul> <li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> <li><code>stdout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://nodejs.org/api/buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> <li><code>stderr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://nodejs.org/api/buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> </ul> </li> <li>Returns: <a href="https://nodejs.org/api/child_process.html#child_process_class_childprocess" class="type"><ChildProcess></a></li> </ul> <p>Spawns a shell then executes the <code>command</code> within that shell, buffering any generated output. The <code>command</code> string passed to the exec function is processed directly by the shell and special characters (vary based on <a href="https://en.wikipedia.org/wiki/List_of_command-line_interpreters">shell</a>) need to be dealt with accordingly:</p> <pre><code class="language-js">exec('"/path/to/test file/test.sh" arg1 arg2'); // Double quotes are used so that the space in the path is not interpreted as // a delimiter of multiple arguments. exec('echo "The \\$HOME variable is $HOME"'); // The $HOME variable is escaped in the first instance, but not in the second. </code></pre> <p><strong>Never pass unsanitized user input to this function. Any input containing shell metacharacters may be used to trigger arbitrary command execution.</strong></p> <p>If a <code>callback</code> function is provided, it is called with the arguments <code>(error, stdout, stderr)</code>. On success, <code>error</code> will be <code>null</code>. On error, <code>error</code> will be an instance of <a href="https://nodejs.org/api/errors.html#errors_class_error"><code>Error</code></a>. The <code>error.code</code> property will be the exit code of the child process while <code>error.signal</code> will be set to the signal that terminated the process. Any exit code other than <code>0</code> is considered to be an error.</p> <p>The <code>stdout</code> and <code>stderr</code> arguments passed to the callback will contain the stdout and stderr output of the child process. By default, Node.js will decode the output as UTF-8 and pass strings to the callback. The <code>encoding</code> option can be used to specify the character encoding used to decode the stdout and stderr output. If <code>encoding</code> is <code>'buffer'</code>, or an unrecognized character encoding, <code>Buffer</code> objects will be passed to the callback instead.</p> <pre><code class="language-js">const { exec } = require('child_process'); exec('cat *.js missing_file | wc -l', (error, stdout, stderr) => { if (error) { console.error(`exec error: ${error}`); return; } console.log(`stdout: ${stdout}`); console.error(`stderr: ${stderr}`); }); </code></pre> <p>If <code>timeout</code> is greater than <code>0</code>, the parent will send the signal identified by the <code>killSignal</code> property (the default is <code>'SIGTERM'</code>) if the child runs longer than <code>timeout</code> milliseconds.</p> <p>Unlike the <a href="http://man7.org/linux/man-pages/man3/exec.3.html"><code>exec(3)</code></a> POSIX system call, <code>child_process.exec()</code> does not replace the existing process and uses a shell to execute the command.</p> <p>If this method is invoked as its <a href="https://nodejs.org/api/util.html#util_util_promisify_original"><code>util.promisify()</code></a>ed version, it returns a <code>Promise</code> for an <code>Object</code> with <code>stdout</code> and <code>stderr</code> properties. The returned <code>ChildProcess</code> instance is attached to the <code>Promise</code> as a <code>child</code> property. In case of an error (including any error resulting in an exit code other than 0), a rejected promise is returned, with the same <code>error</code> object given in the callback, but with two additional properties <code>stdout</code> and <code>stderr</code>.</p> <pre><code class="language-js">const util = require('util'); const exec = util.promisify(require('child_process').exec); async function lsExample() { const { stdout, stderr } = await exec('ls'); console.log('stdout:', stdout); console.error('stderr:', stderr); } lsExample(); </code></pre> <h3>child_process.execFile(file[, args][, options][, callback])<a class="srclink" href="https://github.com/nodejs/node/blob/3a2e75d9a5c31d20e429d505b82dd182e33f459a/lib/child_process.js#L178">[src]</a><span><a class="mark" href="#child_process_child_process_execfile_file_args_options_callback" id="child_process_child_process_execfile_file_args_options_callback">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.8.0</td> <td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> <tr><td>v0.1.91</td> <td><p><span>Added in: v0.1.91</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>file</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name or path of the executable file to run.</li> <li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments.</li> <li> <p><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></p> <ul> <li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Current working directory of the child process.</li> <li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'utf8'</code></li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> <strong>Default:</strong> <code>0</code></li> <li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at <a href="#child_process_maxbuffer_and_unicode"><code>maxBuffer</code> and Unicode</a>. <strong>Default:</strong> <code>1024 * 1024</code>.</li> <li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>'SIGTERM'</code></li> <li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> <li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> <li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would normally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> <li><code>windowsVerbatimArguments</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> No quoting or escaping of arguments is done on Windows. Ignored on Unix. <strong>Default:</strong> <code>false</code>.</li> <li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>true</code>, runs <code>command</code> inside of a shell. Uses <code>'/bin/sh'</code> on Unix, and <code>process.env.ComSpec</code> on Windows. A different shell can be specified as a string. See <a href="#child_process_shell_requirements">Shell Requirements</a> and <a href="#child_process_default_windows_shell">Default Windows Shell</a>. <strong>Default:</strong> <code>false</code> (no shell).</li> </ul> </li> <li> <p><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called with the output when process terminates.</p> <ul> <li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> <li><code>stdout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://nodejs.org/api/buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> <li><code>stderr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://nodejs.org/api/buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> </ul> </li> <li>Returns: <a href="https://nodejs.org/api/child_process.html#child_process_class_childprocess" class="type"><ChildProcess></a></li> </ul> <p>The <code>child_process.execFile()</code> function is similar to <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a> except that it does not spawn a shell by default. Rather, the specified executable <code>file</code> is spawned directly as a new process making it slightly more efficient than <a href="#child_process_child_process_exec_command_options_callback"><code>child_process.exec()</code></a>.</p> <p>The sam