doc: change child to subprocess

Backport-PR-URL: #14633
PR-URL: #14578
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Refael Ackermann <[email protected]>

Author: Trott

doc/api/child_process.md

@@ -280,7 +280,7 @@ The `child_process.fork()` method is a special case of
 Like [`child_process.spawn()`][], a [`ChildProcess`][] object is returned. The returned
 [`ChildProcess`][] will have an additional communication channel built-in that
 allows messages to be passed back and forth between the parent and child. See
-[`child.send()`][] for details.
+[`subprocess.send()`][] for details.
 
 It is important to keep in mind that spawned Node.js child processes are
 independent of the parent with exception of the IPC communication channel
@@ -412,10 +412,10 @@ Example of checking for failed exec:
 
 ```js
 const spawn = require('child_process').spawn;
-const child = spawn('bad_command');
+const subprocess = spawn('bad_command');
 
-child.on('error', (err) => {
-  console.log('Failed to start child process.');
+subprocess.on('error', (err) => {
+  console.log('Failed to start subprocess.');
 });
 ```
 
@@ -443,10 +443,10 @@ child processes may continue running after the parent exits regardless of
 whether they are detached or not.  See setsid(2) for more information.
 
 By default, the parent will wait for the detached child to exit. To prevent
-the parent from waiting for a given `child`, use the `child.unref()` method.
-Doing so will cause the parent's event loop to not include the child in its
-reference count, allowing the parent to exit independently of the child, unless
-there is an established IPC channel between the child and parent.
+the parent from waiting for a given `subprocess`, use the `subprocess.unref()`
+method. Doing so will cause the parent's event loop to not include the child in
+its reference count, allowing the parent to exit independently of the child,
+unless there is an established IPC channel between the child and parent.
 
 When using the `detached` option to start a long-running process, the process
 will not stay running in the background after the parent exits unless it is
@@ -460,12 +460,12 @@ Example of a long-running process, by detaching and also ignoring its parent
 ```js
 const spawn = require('child_process').spawn;
 
-const child = spawn(process.argv[0], ['child_program.js'], {
+const subprocess = spawn(process.argv[0], ['child_program.js'], {
   detached: true,
   stdio: 'ignore'
 });
 
-child.unref();
+subprocess.unref();
 ```
 
 Alternatively one can redirect the child process' output into files:
@@ -476,12 +476,12 @@ const spawn = require('child_process').spawn;
 const out = fs.openSync('./out.log', 'a');
 const err = fs.openSync('./out.log', 'a');
 
-const child = spawn('prg', [], {
+const subprocess = spawn('prg', [], {
   detached: true,
   stdio: [ 'ignore', out, err ]
 });
 
-child.unref();
+subprocess.unref();
 ```
 
 #### options.stdio
@@ -491,9 +491,10 @@ added: v0.7.10
 
 The `options.stdio` option is used to configure the pipes that are established
 between the parent and child process. By default, the child's stdin, stdout,
-and stderr are redirected to corresponding [`child.stdin`][], [`child.stdout`][], and
-[`child.stderr`][] streams on the [`ChildProcess`][] object. This is equivalent to
-setting the `options.stdio` equal to `['pipe', 'pipe', 'pipe']`.
+and stderr are redirected to corresponding [`subprocess.stdin`][],
+[`subprocess.stdout`][], and [`subprocess.stderr`][] streams on the
+[`ChildProcess`][] object. This is equivalent to setting the `options.stdio`
+equal to `['pipe', 'pipe', 'pipe']`.
 
 For convenience, `options.stdio` may be one of the following strings:
 
@@ -509,17 +510,18 @@ pipes between the parent and child. The value is one of the following:
 
 1. `'pipe'` - Create a pipe between the child process and the parent process.
    The parent end of the pipe is exposed to the parent as a property on the
-   `child_process` object as [`child.stdio[fd]`][`stdio`]. Pipes created for
-   fds 0 - 2 are also available as [`child.stdin`][], [`child.stdout`][]
-   and [`child.stderr`][], respectively.
+   `child_process` object as [`subprocess.stdio[fd]`][`stdio`]. Pipes created
+   for fds 0 - 2 are also available as [`subprocess.stdin`][],
+   [`subprocess.stdout`][] and [`subprocess.stderr`][], respectively.
 2. `'ipc'` - Create an IPC channel for passing messages/file descriptors
    between parent and child. A [`ChildProcess`][] may have at most *one* IPC stdio
-   file descriptor. Setting this option enables the [`child.send()`][] method.
-   If the child writes JSON messages to this file descriptor, the
-   [`child.on('message')`][`'message'`] event handler will be triggered in the parent.
-   If the child is a Node.js process, the presence of an IPC channel will enable
-   [`process.send()`][], [`process.disconnect()`][], [`process.on('disconnect')`][], and
-   [`process.on('message')`] within the child.
+   file descriptor. Setting this option enables the [`subprocess.send()`][]
+   method. If the child writes JSON messages to this file descriptor, the
+   [`subprocess.on('message')`][`'message'`] event handler will be triggered in
+   the parent. If the child is a Node.js process, the presence of an IPC channel
+   will enable [`process.send()`][], [`process.disconnect()`][],
+   [`process.on('disconnect')`][], and [`process.on('message')`] within the
+   child.
 3. `'ignore'` - Instructs Node.js to ignore the fd in the child. While Node.js
    will always open fds 0 - 2 for the processes it spawns, setting the fd to
    `'ignore'` will cause Node.js to open `/dev/null` and attach it to the
@@ -739,9 +741,10 @@ added: v0.7.2
 -->
 
 The `'disconnect'` event is emitted after calling the
-[`child.disconnect()`][] method in parent process or [`process.disconnect()`][] in child process. After
-disconnecting it is no longer possible to send or receive messages, and the
-[`child.connected`][] property is `false`.
+[`subprocess.disconnect()`][] method in parent process or
+[`process.disconnect()`][] in child process. After disconnecting it is no longer
+possible to send or receive messages, and the [`subprocess.connected`][]
+property is `false`.
 
 ### Event: 'error'
 
@@ -757,7 +760,7 @@ Note that the `'exit'` event may or may not fire after an error has occurred.
 If you are listening to both the `'exit'` and `'error'` events, it is important
 to guard against accidentally invoking handler functions multiple times.
 
-See also [`child.kill()`][] and [`child.send()`][].
+See also [`subprocess.kill()`][] and [`subprocess.send()`][].
 
 ### Event: 'exit'
 <!-- YAML
@@ -794,46 +797,49 @@ added: v0.5.9
 The `'message'` event is triggered when a child process uses [`process.send()`][]
 to send messages.
 
-### child.connected
+<a name="child_process_child_connected"></a>
+### subprocess.connected
 <!-- YAML
 added: v0.7.2
 -->
 
-* {boolean} Set to `false` after `child.disconnect()` is called
+* {boolean} Set to `false` after `subprocess.disconnect()` is called
 
-The `child.connected` property indicates whether it is still possible to send
-and receive messages from a child process. When `child.connected` is `false`, it
-is no longer possible to send or receive messages.
+The `subprocess.connected` property indicates whether it is still possible to
+send and receive messages from a child process. When `subprocess.connected` is
+`false`, it is no longer possible to send or receive messages.
 
-### child.disconnect()
+<a name="child_process_child_disconnect"></a>
+### subprocess.disconnect()
 <!-- YAML
 added: v0.7.2
 -->
 
 Closes the IPC channel between parent and child, allowing the child to exit
 gracefully once there are no other connections keeping it alive. After calling
-this method the `child.connected` and `process.connected` properties in both
-the parent and child (respectively) will be set to `false`, and it will be no
-longer possible to pass messages between the processes.
+this method the `subprocess.connected` and `process.connected` properties in
+both the parent and child (respectively) will be set to `false`, and it will be
+no longer possible to pass messages between the processes.
 
 The `'disconnect'` event will be emitted when there are no messages in the
 process of being received. This will most often be triggered immediately after
-calling `child.disconnect()`.
+calling `subprocess.disconnect()`.
 
 Note that when the child process is a Node.js instance (e.g. spawned using
 [`child_process.fork()`]), the `process.disconnect()` method can be invoked
 within the child process to close the IPC channel as well.
 
-### child.kill([signal])
+<a name="child_process_child_kill_signal"></a>
+### subprocess.kill([signal])
 <!-- YAML
 added: v0.1.90
 -->
 
 * `signal` {string}
 
-The `child.kill()` methods sends a signal to the child process. If no argument
-is given, the process will be sent the `'SIGTERM'` signal. See signal(7) for
-a list of available signals.
+The `subprocess.kill()` methods sends a signal to the child process. If no
+argument is given, the process will be sent the `'SIGTERM'` signal. See
+signal(7) for a list of available signals.
 
 ```js
 const spawn = require('child_process').spawn;
@@ -868,7 +874,7 @@ as in this example:
 'use strict';
 const spawn = require('child_process').spawn;
 
-const child = spawn(
+const subprocess = spawn(
   'sh',
   [
     '-c',
@@ -881,11 +887,12 @@ const child = spawn(
 );
 
 setTimeout(() => {
-  child.kill(); // does not terminate the node process in the shell
+  subprocess.kill(); // does not terminate the node process in the shell
 }, 2000);
 ```
 
-### child.pid
+<a name="child_process_child_pid"></a>
+### subprocess.pid
 <!-- YAML
 added: v0.1.90
 -->
@@ -904,7 +911,8 @@ console.log(`Spawned child pid: ${grep.pid}`);
 grep.stdin.end();
 ```
 
-### child.send(message[, sendHandle[, options]][, callback])
+<a name="child_process_child_send_message_sendhandle_options_callback"></a>
+### subprocess.send(message[, sendHandle[, options]][, callback])
 <!-- YAML
 added: v0.5.9
 -->
@@ -916,9 +924,10 @@ added: v0.5.9
 * Returns: {boolean}
 
 When an IPC channel has been established between the parent and child (
-i.e. when using [`child_process.fork()`][]), the `child.send()` method can be
-used to send messages to the child process. When the child process is a Node.js
-instance, these messages can be received via the [`process.on('message')`][] event.
+i.e. when using [`child_process.fork()`][]), the `subprocess.send()` method can
+be used to send messages to the child process. When the child process is a
+Node.js instance, these messages can be received via the
+[`process.on('message')`][] event.
 
 For example, in the parent script:
 
@@ -954,8 +963,8 @@ for use within Node.js core and will not be emitted in the child's
 Applications should avoid using such messages or listening for
 `'internalMessage'` events as it is subject to change without notice.
 
-The optional `sendHandle` argument that may be passed to `child.send()` is for
-passing a TCP server or socket object to the child process. The child will
+The optional `sendHandle` argument that may be passed to `subprocess.send()` is
+for passing a TCP server or socket object to the child process. The child will
 receive the object as the second argument passed to the callback function
 registered on the [`process.on('message')`][] event. Any data that is received
 and buffered in the socket will not be sent to the child.
@@ -976,7 +985,7 @@ If no `callback` function is provided and the message cannot be sent, an
 `'error'` event will be emitted by the [`ChildProcess`][] object. This can happen,
 for instance, when the child process has already exited.
 
-`child.send()` will return `false` if the channel has closed or when the
+`subprocess.send()` will return `false` if the channel has closed or when the
 backlog of unsent messages exceeds a threshold that makes it unwise to send
 more. Otherwise, the method returns `true`. The `callback` function can be
 used to implement flow control.
@@ -987,15 +996,15 @@ The `sendHandle` argument can be used, for instance, to pass the handle of
 a TCP server object to the child process as illustrated in the example below:
 
 ```js
-const child = require('child_process').fork('child.js');
+const subprocess = require('child_process').fork('subprocess.js');
 
 // Open up the server object and send the handle.
 const server = require('net').createServer();
 server.on('connection', (socket) => {
   socket.end('handled by parent');
 });
 server.listen(1337, () => {
-  child.send('server', server);
+  subprocess.send('server', server);
 });
 ```
 
@@ -1026,8 +1035,8 @@ socket to the child process. The example below spawns two children that each
 handle connections with "normal" or "special" priority:
 
 ```js
-const normal = require('child_process').fork('child.js', ['normal']);
-const special = require('child_process').fork('child.js', ['special']);
+const normal = require('child_process').fork('subprocess.js', ['normal']);
+const special = require('child_process').fork('subprocess.js', ['special']);
 
 // Open up the server and send sockets to child
 const server = require('net').createServer();
@@ -1044,8 +1053,8 @@ server.on('connection', (socket) => {
 server.listen(1337);
 ```
 
-The `child.js` would receive the socket handle as the second argument passed
-to the event callback function:
+The `subprocess.js` would receive the socket handle as the second argument
+passed to the event callback function:
 
 ```js
 process.on('message', (m, socket) => {
@@ -1063,7 +1072,8 @@ this occurs.
 *Note: this function uses [`JSON.stringify()`][] internally to serialize the
 `message`.*
 
-### child.stderr
+<a name="child_process_child_stderr"></a>
+### subprocess.stderr
 <!-- YAML
 added: v0.1.90
 -->
@@ -1075,10 +1085,11 @@ A `Readable Stream` that represents the child process's `stderr`.
 If the child was spawned with `stdio[2]` set to anything other than `'pipe'`,
 then this will be `null`.
 
-`child.stderr` is an alias for `child.stdio[2]`. Both properties will refer to
-the same value.
+`subprocess.stderr` is an alias for `subprocess.stdio[2]`. Both properties will
+refer to the same value.
 
-### child.stdin
+<a name="child_process_child_stdin"></a>
+### subprocess.stdin
 <!-- YAML
 added: v0.1.90
 -->
@@ -1093,10 +1104,11 @@ continue until this stream has been closed via `end()`.*
 If the child was spawned with `stdio[0]` set to anything other than `'pipe'`,
 then this will be `null`.
 
-`child.stdin` is an alias for `child.stdio[0]`. Both properties will refer to
-the same value.
+`subprocess.stdin` is an alias for `subprocess.stdio[0]`. Both properties will
+refer to the same value.
 
-### child.stdio
+<a name="child_process_child_stdio"></a>
+### subprocess.stdio
 <!-- YAML
 added: v0.7.10
 -->
@@ -1105,38 +1117,39 @@ added: v0.7.10
 
 A sparse array of pipes to the child process, corresponding with positions in
 the [`stdio`][] option passed to [`child_process.spawn()`][] that have been set
-to the value `'pipe'`. Note that `child.stdio[0]`, `child.stdio[1]`, and
-`child.stdio[2]` are also available as `child.stdin`, `child.stdout`, and
-`child.stderr`, respectively.
+to the value `'pipe'`. Note that `subprocess.stdio[0]`, `subprocess.stdio[1]`,
+and `subprocess.stdio[2]` are also available as `subprocess.stdin`,
+`subprocess.stdout`, and `subprocess.stderr`, respectively.
 
 In the following example, only the child's fd `1` (stdout) is configured as a
-pipe, so only the parent's `child.stdio[1]` is a stream, all other values in
-the array are `null`.
+pipe, so only the parent's `subprocess.stdio[1]` is a stream, all other values
+in the array are `null`.
 
 ```js
 const assert = require('assert');
 const fs = require('fs');
 const child_process = require('child_process');
 
-const child = child_process.spawn('ls', {
+const subprocess = child_process.spawn('ls', {
   stdio: [
     0, // Use parent's stdin for child
     'pipe', // Pipe child's stdout to parent
     fs.openSync('err.out', 'w') // Direct child's stderr to a file
   ]
 });
 
-assert.strictEqual(child.stdio[0], null);
-assert.strictEqual(child.stdio[0], child.stdin);
+assert.strictEqual(subprocess.stdio[0], null);
+assert.strictEqual(subprocess.stdio[0], subprocess.stdin);
 
-assert(child.stdout);
-assert.strictEqual(child.stdio[1], child.stdout);
+assert(subprocess.stdout);
+assert.strictEqual(subprocess.stdio[1], subprocess.stdout);
 
-assert.strictEqual(child.stdio[2], null);
-assert.strictEqual(child.stdio[2], child.stderr);
+assert.strictEqual(subprocess.stdio[2], null);
+assert.strictEqual(subprocess.stdio[2], subprocess.stderr);
 ```
 
-### child.stdout
+<a name="child_process_child_stdout"></a>
+### subprocess.stdout
 <!-- YAML
 added: v0.1.90
 -->
@@ -1148,8 +1161,8 @@ A `Readable Stream` that represents the child process's `stdout`.
 If the child was spawned with `stdio[1]` set to anything other than `'pipe'`,
 then this will be `null`.
 
-`child.stdout` is an alias for `child.stdio[1]`. Both properties will refer
-to the same value.
+`subprocess.stdout` is an alias for `subprocess.stdio[1]`. Both properties will
+refer to the same value.
 
 ## `maxBuffer` and Unicode
 
@@ -1162,13 +1175,13 @@ to `stdout` although there are only 4 characters.
 [`'error'`]: #child_process_event_error
 [`'exit'`]: #child_process_event_exit
 [`'message'`]: #child_process_event_message
-[`child.connected`]: #child_process_child_connected
-[`child.disconnect()`]: #child_process_child_disconnect
-[`child.kill()`]: #child_process_child_kill_signal
-[`child.send()`]: #child_process_child_send_message_sendhandle_options_callback
-[`child.stderr`]: #child_process_child_stderr
-[`child.stdin`]: #child_process_child_stdin
-[`child.stdout`]: #child_process_child_stdout
+[`subprocess.connected`]: #child_process_subprocess_connected
+[`subprocess.disconnect()`]: #child_process_subprocess_disconnect
+[`subprocess.kill()`]: #child_process_subprocess_kill_signal
+[`subprocess.send()`]: #child_process_subprocess_send_message_sendhandle_options_callback
+[`subprocess.stderr`]: #child_process_subprocess_stderr
+[`subprocess.stdin`]: #child_process_subprocess_stdin
+[`subprocess.stdout`]: #child_process_subprocess_stdout
 [`child_process.exec()`]: #child_process_child_process_exec_command_options_callback
 [`child_process.execFile()`]: #child_process_child_process_execfile_file_args_options_callback
 [`child_process.execFileSync()`]: #child_process_child_process_execfilesync_file_args_options