diff --git a/doc/api/child_process.md b/doc/api/child_process.md index 2c8665be58f548..3a9c4016e37d0f 100644 --- a/doc/api/child_process.md +++ b/doc/api/child_process.md @@ -3,8 +3,8 @@ Stability: 2 - Stable The `child_process` module provides the ability to spawn child processes in -a manner that is similar, but not identical, to [`popen(3)`][]. This capability -is primarily provided by the `child_process.spawn()` function: +a manner that is similar, but not identical, to popen(3). This capability +is primarily provided by the [`child_process.spawn()`][] function: ```js const spawn = require('child_process').spawn; @@ -29,27 +29,27 @@ through these pipes in a non-blocking way. *Note, however, that some programs use line-buffered I/O internally. While that does not affect Node.js, it can mean that data sent to the child process may not be immediately consumed.* -The `child_process.spawn()` method spawns the child process asynchronously, -without blocking the Node.js event loop. The `child_process.spawnSync()` +The [`child_process.spawn()`][] method spawns the child process asynchronously, +without blocking the Node.js event loop. The [`child_process.spawnSync()`][] function provides equivalent functionality in a synchronous manner that blocks the event loop until the spawned process either exits or is terminated. For convenience, the `child_process` module provides a handful of synchronous and asynchronous alternatives to [`child_process.spawn()`][] and [`child_process.spawnSync()`][]. *Note that each of these alternatives are -implemented on top of `child_process.spawn()` or `child_process.spawnSync()`.* +implemented on top of [`child_process.spawn()`][] or [`child_process.spawnSync()`][].* - * `child_process.exec()`: spawns a shell and runs a command within that shell, + * [`child_process.exec()`][]: spawns a shell and runs a command within that shell, passing the `stdout` and `stderr` to a callback function when complete. - * `child_process.execFile()`: similar to `child_process.exec()` except that + * [`child_process.execFile()`][]: similar to [`child_process.exec()`][] except that it spawns the command directly without first spawning a shell. - * `child_process.fork()`: spawns a new Node.js process and invokes a + * [`child_process.fork()`][]: 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. - * `child_process.execSync()`: a synchronous version of - `child_process.exec()` that *will* block the Node.js event loop. - * `child_process.execFileSync()`: a synchronous version of - `child_process.execFile()` that *will* block the Node.js event loop. + * [`child_process.execSync()`][]: a synchronous version of + [`child_process.exec()`][] that *will* block the Node.js event loop. + * [`child_process.execFileSync()`][]: a synchronous version of + [`child_process.execFile()`][] that *will* block the Node.js event loop. For certain use cases, such as automating shell scripts, the [synchronous counterparts][] may be more convenient. In many cases, however, @@ -58,8 +58,8 @@ stalling the event loop while spawned processes complete. ## Asynchronous Process Creation -The `child_process.spawn()`, `child_process.fork()`, `child_process.exec()`, -and `child_process.execFile()` methods all follow the idiomatic asynchronous +The [`child_process.spawn()`][], [`child_process.fork()`][], [`child_process.exec()`][], +and [`child_process.execFile()`][] methods all follow the idiomatic asynchronous programming pattern typical of other Node.js APIs. Each of the methods returns a [`ChildProcess`][] instance. These objects @@ -67,22 +67,22 @@ implement the Node.js [`EventEmitter`][] API, allowing the parent process to register listener functions that are called when certain events occur during the life cycle of the child process. -The `child_process.exec()` and `child_process.execFile()` methods additionally +The [`child_process.exec()`][] and [`child_process.execFile()`][] methods additionally allow for an optional `callback` function to be specified that is invoked when the child process terminates. ### Spawning `.bat` and `.cmd` files on Windows -The importance of the distinction between `child_process.exec()` and -`child_process.execFile()` can vary based on platform. On Unix-type operating -systems (Unix, Linux, OSX) `child_process.execFile()` can be more efficient +The importance of the distinction between [`child_process.exec()`][] and +[`child_process.execFile()`][] can vary based on platform. On Unix-type operating +systems (Unix, Linux, OSX) [`child_process.execFile()`][] can be more efficient because it does not spawn a shell. On Windows, however, `.bat` and `.cmd` files are not executable on their own without a terminal, and therefore cannot -be launched using `child_process.execFile()`. When running on Windows, `.bat` -and `.cmd` files can be invoked using `child_process.spawn()` with the `shell` -option set, with `child_process.exec()`, or by spawning `cmd.exe` and passing +be launched using [`child_process.execFile()`][]. When running on Windows, `.bat` +and `.cmd` files can be invoked using [`child_process.spawn()`][] with the `shell` +option set, with [`child_process.exec()`][], or by spawning `cmd.exe` and passing the `.bat` or `.cmd` file as an argument (which is what the `shell` option and -`child_process.exec()` do). +[`child_process.exec()`][] do). ```js // On Windows Only ... @@ -118,15 +118,15 @@ exec('my.bat', (err, stdout, stderr) => { * `options` {Object} * `cwd` {String} Current working directory of the child process * `env` {Object} Environment key-value pairs - * `encoding` {String} (Default: 'utf8') + * `encoding` {String} (Default: `'utf8'`) * `shell` {String} Shell to execute the command with - (Default: '/bin/sh' on UNIX, 'cmd.exe' on Windows, The shell should + (Default: `'/bin/sh'` on UNIX, `'cmd.exe'` on Windows, The shell should understand the `-c` switch on UNIX or `/s /c` on Windows. On Windows, command line parsing should be compatible with `cmd.exe`.) - * `timeout` {Number} (Default: 0) + * `timeout` {Number} (Default: `0`) * [`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on - stdout or stderr - if exceeded child process is killed (Default: `200*1024`) - * `killSignal` {String} (Default: 'SIGTERM') + stdout or stderr - if exceeded child process is killed (Default: `200\*1024`) + * `killSignal` {String} (Default: `'SIGTERM'`) * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * `callback` {Function} called with the output when process terminates @@ -182,7 +182,7 @@ If `timeout` is greater than `0`, the parent will send the the signal identified by the `killSignal` property (the default is `'SIGTERM'`) if the child runs longer than `timeout` milliseconds. -*Note: Unlike the `exec()` POSIX system call, `child_process.exec()` does not +*Note: Unlike the exec(3) POSIX system call, `child_process.exec()` does not replace the existing process and uses a shell to execute the command.* ### child_process.execFile(file[, args][, options][, callback]) @@ -192,11 +192,11 @@ replace the existing process and uses a shell to execute the command.* * `options` {Object} * `cwd` {String} Current working directory of the child process * `env` {Object} Environment key-value pairs - * `encoding` {String} (Default: 'utf8') - * `timeout` {Number} (Default: 0) + * `encoding` {String} (Default: `'utf8'`) + * `timeout` {Number} (Default: `0`) * [`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on - stdout or stderr - if exceeded child process is killed (Default: 200\*1024) - * `killSignal` {String} (Default: 'SIGTERM') + stdout or stderr - if exceeded child process is killed (Default: `200\*1024`) + * `killSignal` {String} (Default: `'SIGTERM'`) * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * `callback` {Function} called with the output when process terminates @@ -210,7 +210,7 @@ except that it does not spawn a shell. Rather, the specified executable `file` is spawned directly as a new process making it slightly more efficient than [`child_process.exec()`][]. -The same options as `child_process.exec()` are supported. Since a shell is not +The same options as [`child_process.exec()`][] are supported. Since a shell is not spawned, behaviors such as I/O redirection and file globbing are not supported. ```js @@ -240,20 +240,20 @@ the callback instead. * `execPath` {String} Executable used to create the child process * `execArgv` {Array} List of string arguments passed to the executable (Default: `process.execArgv`) - * `silent` {Boolean} If true, stdin, stdout, and stderr of the child will be + * `silent` {Boolean} If `true`, stdin, stdout, and stderr of the child will be piped to the parent, otherwise they will be inherited from the parent, see the `'pipe'` and `'inherit'` options for [`child_process.spawn()`][]'s - [`stdio`][] for more details (default is false) + [`stdio`][] for more details (Default: `false`) * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * Return: {ChildProcess} The `child_process.fork()` method is a special case of [`child_process.spawn()`][] used specifically to spawn new Node.js processes. -Like `child_process.spawn()`, a `ChildProcess` object is returned. The returned -`ChildProcess` will have an additional communication channel built-in that +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 -[`ChildProcess#send()`][] for details. +[`child.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 @@ -263,7 +263,7 @@ required, spawning a large number of child Node.js processes is not recommended. By default, `child_process.fork()` will spawn new Node.js instances using the -`process.execPath` of the parent process. The `execPath` property in the +[`process.execPath`][] of the parent process. The `execPath` property in the `options` object allows for an alternative execution path to be used. Node.js processes launched with a custom `execPath` will communicate with the @@ -271,7 +271,7 @@ parent process using the file descriptor (fd) identified using the environment variable `NODE_CHANNEL_FD` on the child process. The input and output on this fd is expected to be line delimited JSON objects. -*Note: Unlike the `fork()` POSIX system call, [`child_process.fork()`][] does +*Note: Unlike the fork(2) POSIX system call, `child_process.fork()` does not clone the current process.* ### child_process.spawn(command[, args][, options]) @@ -282,14 +282,14 @@ not clone the current process.* * `cwd` {String} Current working directory of the child process * `env` {Object} Environment key-value pairs * `stdio` {Array|String} Child's stdio configuration. (See - [`options.stdio`][]) + [`options.stdio`][`stdio`]) * `detached` {Boolean} Prepare child to run independently of its parent process. Specific behavior depends on the platform, see [`options.detached`][]) * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * `shell` {Boolean|String} If `true`, runs `command` inside of a shell. Uses - '/bin/sh' on UNIX, and 'cmd.exe' on Windows. A different shell can be + `'/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 `/s /c` on Windows. Defaults to `false` (no shell). * return: {ChildProcess} @@ -311,7 +311,7 @@ Use `cwd` to specify the working directory from which the process is spawned. If not given, the default is to inherit the current working directory. Use `env` to specify environment variables that will be visible to the new -process, the default is `process.env`. +process, the default is [`process.env`][]. Example of running `ls -lh /usr`, capturing `stdout`, `stderr`, and the exit code: @@ -334,7 +334,7 @@ ls.on('close', (code) => { ``` -Example: A very elaborate way to run 'ps ax | grep ssh' +Example: A very elaborate way to run `ps ax | grep ssh` ```js const spawn = require('child_process').spawn; @@ -393,7 +393,7 @@ disabled*. On non-Windows platforms, if `options.detached` is set to `true`, the child process will be made the leader of a new process group and session. Note that child processes may continue running after the parent exits regardless of -whether they are detached or not. See `setsid(2)` for more information. +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. @@ -441,8 +441,8 @@ child.unref(); 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 +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']`. For convenience, `options.stdio` may be one of the following strings: @@ -452,29 +452,29 @@ For convenience, `options.stdio` may be one of the following strings: * `'inherit'` - equivalent to `[process.stdin, process.stdout, process.stderr]` or `[0,1,2]` -Otherwise, the value of `option.stdio` is an array where each index corresponds +Otherwise, the value of `options.stdio` is an array where each index corresponds to an fd in the child. The fds 0, 1, and 2 correspond to stdin, stdout, and stderr, respectively. Additional fds can be specified to create additional 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 `ChildProcess.stdio[fd]`. Pipes created for - fds 0 - 2 are also available as ChildProcess.stdin, ChildProcess.stdout - and ChildProcess.stderr, respectively. + `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. 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 ChildProcess.send() method. + 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 - `ChildProcess.on('message')` event handler will be triggered in the parent. + [`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. + [`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 child's fd. -4. `Stream` object - Share a readable or writable stream that refers to a tty, +4. {Stream} object - Share a readable or writable stream that refers to a tty, file, socket, or a pipe with the child process. The stream's underlying file descriptor is duplicated in the child process to the fd that corresponds to the index in the `stdio` array. Note that the stream must @@ -482,7 +482,7 @@ pipes between the parent and child. The value is one of the following: event has occurred). 5. Positive integer - The integer value is interpreted as a file descriptor that is is currently open in the parent process. It is shared with the child - process, similar to how `Stream` objects can be shared. + process, similar to how {Stream} objects can be shared. 6. `null`, `undefined` - Use default value. For stdio fds 0, 1 and 2 (in other words, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the default is `'ignore'`. @@ -506,7 +506,7 @@ spawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] }); *It is worth noting that when an IPC channel is established between the parent and child processes, and the child is a Node.js process, the child is launched with the IPC channel unreferenced (using `unref()`) until the -child registers an event handler for the `process.on('disconnected')` event. +child registers an event handler for the [`process.on('disconnect')`][] event. This allows the child to exit normally without the process being held open by the open IPC channel.* @@ -514,8 +514,8 @@ See also: [`child_process.exec()`][] and [`child_process.fork()`][] ## Synchronous Process Creation -The `child_process.spawnSync()`, `child_process.execSync()`, and -`child_process.execFileSync()` methods are **synchronous** and **WILL** block +The [`child_process.spawnSync()`][], [`child_process.execSync()`][], and +[`child_process.execFileSync()`][] methods are **synchronous** and **WILL** block the Node.js event loop, pausing execution of any additional code until the spawned process exits. @@ -532,23 +532,23 @@ configuration at startup. * `input` {String|Buffer} The value which will be passed as stdin to the spawned process - supplying this value will override `stdio[0]` - * `stdio` {Array} Child's stdio configuration. (Default: 'pipe') + * `stdio` {Array} Child's stdio configuration. (Default: `'pipe'`) - `stderr` by default will be output to the parent process' stderr unless `stdio` is specified * `env` {Object} Environment key-value pairs * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * `timeout` {Number} In milliseconds the maximum amount of time the process - is allowed to run. (Default: undefined) + is allowed to run. (Default: `undefined`) * `killSignal` {String} The signal value to be used when the spawned process - will be killed. (Default: 'SIGTERM') + will be killed. (Default: `'SIGTERM'`) * [`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed - * `encoding` {String} The encoding used for all stdio inputs and outputs. (Default: 'buffer') + * `encoding` {String} The encoding used for all stdio inputs and outputs. (Default: `'buffer'`) * return: {Buffer|String} The stdout from the command The `child_process.execFileSync()` method is generally identical to -`child_process.execFile()` with the exception that the method will not return +[`child_process.execFile()`][] with the exception that the method will not return until the child process has fully closed. When a timeout has been encountered and `killSignal` is sent, the method won't return until the process has completely exited. *Note that if the child process intercepts and handles @@ -567,28 +567,28 @@ throw. The [`Error`][] object will contain the entire result from * `input` {String|Buffer} The value which will be passed as stdin to the spawned process - supplying this value will override `stdio[0]` - * `stdio` {Array} Child's stdio configuration. (Default: 'pipe') + * `stdio` {Array} Child's stdio configuration. (Default: `'pipe'`) - `stderr` by default will be output to the parent process' stderr unless `stdio` is specified * `env` {Object} Environment key-value pairs * `shell` {String} Shell to execute the command with - (Default: '/bin/sh' on UNIX, 'cmd.exe' on Windows, The shell should + (Default: `'/bin/sh'` on UNIX, `'cmd.exe'` on Windows, The shell should understand the `-c` switch on UNIX or `/s /c` on Windows. On Windows, command line parsing should be compatible with `cmd.exe`.) * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * `timeout` {Number} In milliseconds the maximum amount of time the process - is allowed to run. (Default: undefined) + is allowed to run. (Default: `undefined`) * `killSignal` {String} The signal value to be used when the spawned process - will be killed. (Default: 'SIGTERM') + will be killed. (Default: `'SIGTERM'`) * [`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed * `encoding` {String} The encoding used for all stdio inputs and outputs. - (Default: 'buffer') + (Default: `'buffer'`) * return: {Buffer|String} The stdout from the command The `child_process.execSync()` method is generally identical to -`child_process.exec()` with the exception that the method will not return until +[`child_process.exec()`][] with the exception that the method will not return until the child process has fully closed. When a timeout has been encountered and `killSignal` is sent, the method won't return until the process has completely exited. *Note that if the child process intercepts and handles the `SIGTERM` @@ -613,15 +613,15 @@ throw. The [`Error`][] object will contain the entire result from * `uid` {Number} Sets the user identity of the process. (See setuid(2).) * `gid` {Number} Sets the group identity of the process. (See setgid(2).) * `timeout` {Number} In milliseconds the maximum amount of time the process - is allowed to run. (Default: undefined) + is allowed to run. (Default: `undefined`) * `killSignal` {String} The signal value to be used when the spawned process - will be killed. (Default: 'SIGTERM') + will be killed. (Default: `'SIGTERM'`) * [`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed * `encoding` {String} The encoding used for all stdio inputs and outputs. - (Default: 'buffer') + (Default: `'buffer'`) * `shell` {Boolean|String} If `true`, runs `command` inside of a shell. Uses - '/bin/sh' on UNIX, and 'cmd.exe' on Windows. A different shell can be + `'/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 `/s /c` on Windows. Defaults to `false` (no shell). * return: {Object} @@ -634,7 +634,7 @@ throw. The [`Error`][] object will contain the entire result from * `error` {Error} The error object if the child process failed or timed out The `child_process.spawnSync()` method is generally identical to -`child_process.spawn()` with the exception that the function will not return +[`child_process.spawn()`][] with the exception that the function will not return until the child process has fully closed. When a timeout has been encountered and `killSignal` is sent, the method won't return until the process has completely exited. Note that if the process intercepts and handles the @@ -643,7 +643,7 @@ process has exited. ## Class: ChildProcess -Instances of the `ChildProcess` class are [`EventEmitters`][] that represent +Instances of the `ChildProcess` class are [`EventEmitters`][`EventEmitter`] that represent spawned child processes. Instances of `ChildProcess` are not intended to be created directly. Rather, @@ -657,15 +657,15 @@ instances of `ChildProcess`. * `signal` {String} the signal by which the child process was terminated. The `'close'` event is emitted when the stdio streams of a child process have -been closed. This is distinct from the `'exit'` event, since multiple +been closed. This is distinct from the [`'exit'`][] event, since multiple processes might share the same stdio streams. ### Event: 'disconnect' The `'disconnect'` event is emitted after calling the -`ChildProcess.disconnect()` method in the parent or child process. After +[`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 -`ChildProcess.connected` property is false. +[`child.connected`][] property is `false`. ### Event: 'error' @@ -681,7 +681,7 @@ 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 [`ChildProcess#kill()`][] and [`ChildProcess#send()`][]. +See also [`child.kill()`][] and [`child.send()`][]. ### Event: 'exit' @@ -701,7 +701,7 @@ Also, note that Node.js establishes signal handlers for `SIGINT` and of those signals. Rather, Node.js will perform a sequence of cleanup actions and then will re-raise the handled signal. -See `waitpid(2)`. +See waitpid(2). ### Event: 'message' @@ -709,15 +709,15 @@ See `waitpid(2)`. * `sendHandle` {Handle} a [`net.Socket`][] or [`net.Server`][] object, or undefined. -The `'message'` event is triggered when a child process uses `process.send()` +The `'message'` event is triggered when a child process uses [`process.send()`][] to send messages. ### child.connected -* {Boolean} Set to false after `.disconnect` is called +* {Boolean} Set to `false` after `child.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 +and receive messages from a child process. When `child.connected` is `false`, it is no longer possible to send or receive messages. ### child.disconnect() @@ -757,7 +757,7 @@ grep.on('close', (code, signal) => { grep.kill('SIGHUP'); ``` -The `ChildProcess` object may emit an `'error'` event if the signal cannot be +The [`ChildProcess`][] object may emit an [`'error'`][] event if the signal cannot be delivered. Sending a signal to a child process that has already exited is not an error but may have unforeseen consequences. Specifically, if the process identifier (PID) has been reassigned to another process, the signal will be @@ -766,7 +766,7 @@ delivered to that process instead which can have unexpected results. Note that while the function is called `kill`, the signal delivered to the child process may not actually terminate the process. -See `kill(2)` for reference. +See kill(2) for reference. Also note: on Linux, child processes of child processes will not be terminated when attempting to kill their parent. This is likely to happen when running a @@ -817,7 +817,7 @@ grep.stdin.end(); 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. +instance, these messages can be received via the [`process.on('message')`][] event. For example, in the parent script: @@ -842,13 +842,13 @@ process.on('message', (m) => { process.send({ foo: 'bar' }); ``` -Child Node.js processes will have a `process.send()` method of their own that +Child Node.js processes will have a [`process.send()`][] method of their own that allows the child to send messages back to the parent. There is a special case when sending a `{cmd: 'NODE_foo'}` message. All messages containing a `NODE_` prefix in its `cmd` property are considered to be reserved for use within Node.js core and will not be emitted in the child's -`process.on('message')` event. Rather, such messages are emitted using the +[`process.on('message')`][] event. Rather, such messages are emitted using the `process.on('internalMessage')` event and are consumed internally by Node.js. Applications should avoid using such messages or listening for `'internalMessage'` events as it is subject to change without notice. @@ -856,7 +856,7 @@ Applications should avoid using such messages or listening for 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 receive the object as the second argument passed to the callback function -registered on the `process.on('message')` event. +registered on the [`process.on('message')`][] event. The `options` argument, if present, is an object used to parameterize the sending of certain types of handles. `options` supports the following @@ -871,7 +871,7 @@ sent but before the child may have received it. The function is called with a single argument: `null` on success, or an [`Error`][] object on failure. 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, +`'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 @@ -914,8 +914,8 @@ can be handled by the parent and some by the child. While the example above uses a server created using the `net` module, `dgram` module servers use exactly the same workflow with the exceptions of listening on -a `'message'` event instead of `'connection'` and using `server.bind` instead of -`server.listen`. This is, however, currently only supported on UNIX platforms. +a `'message'` event instead of `'connection'` and using `server.bind()` instead of +`server.listen()`. This is, however, currently only supported on UNIX platforms. #### Example: sending a socket object @@ -1050,23 +1050,36 @@ although there are only 4 characters: console.log('中文测试'); ``` -[`popen(3)`]: http://linux.die.net/man/3/popen -[`ChildProcess`]: #child_process_child_process +[`'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 [`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 +[`child_process.execSync()`]: #child_process_child_process_execsync_command_options [`child_process.fork()`]: #child_process_child_process_fork_modulepath_args_options [`child_process.spawn()`]: #child_process_child_process_spawn_command_args_options [`child_process.spawnSync()`]: #child_process_child_process_spawnsync_command_args_options -[`ChildProcess#kill()`]: #child_process_child_kill_signal -[`ChildProcess#send()`]: #child_process_child_send_message_sendhandle_options_callback +[`ChildProcess`]: #child_process_child_process [`Error`]: errors.html#errors_class_error -[`EventEmitter`]: events.html#events_class_eventemitter -[`EventEmitters`]: events.html#events_class_eventemitter +[`EventEmitter`]: events.html#events_class_events_eventemitter +[`JSON.stringify()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify +[`maxBuffer`]: #child_process_maxbuffer_and_unicode [`net.Server`]: net.html#net_class_net_server [`net.Socket`]: net.html#net_class_net_socket [`options.detached`]: #child_process_options_detached -[`options.stdio`]: #child_process_options_stdio +[`process.disconnect()`]: process.html#process_process_disconnect +[`process.env`]: process.html#process_process_env +[`process.execPath`]: process.html#process_process_execpath +[`process.on('disconnect')`]: process.html#process_event_disconnect +[`process.on('message')`]: process.html#process_event_message +[`process.send()`]: process.html#process_process_send_message_sendhandle_callback [`stdio`]: #child_process_options_stdio [synchronous counterparts]: #child_process_synchronous_process_creation -[`JSON.stringify()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify -[`maxBuffer`]: #child_process_maxbuffer_and_unicode diff --git a/doc/api/process.md b/doc/api/process.md index 5020ae25d8a146..0951e7cb433525 100644 --- a/doc/api/process.md +++ b/doc/api/process.md @@ -16,6 +16,11 @@ continue. as [`process.exit()`][] or uncaught exceptions, and should not be used as an alternative to the `'exit'` event unless the intention is to schedule more work. +## Event: 'disconnect' + +If process is spawned with an IPC channel, `'disconnect'` will be emitted when +IPC channel is closed. Read more in [child_process `'disconnect'` event][] doc. + ## Event: 'exit' Emitted when the process is about to exit. There is no way to prevent the @@ -52,7 +57,7 @@ event on the child's process object. ## Event: 'rejectionHandled' Emitted whenever a Promise was rejected and an error handler was attached to it -(for example with `.catch()`) later than after an event loop turn. This event +(for example with [`promise.catch()`][]) later than after an event loop turn. This event is emitted with the following arguments: - `p` the promise that was previously emitted in an `'unhandledRejection'` @@ -140,7 +145,7 @@ down the process. It is not safe to resume normal operation after Emitted whenever a `Promise` is rejected and no error handler is attached to the promise within a turn of the event loop. When programming with promises exceptions are encapsulated as rejected promises. Such promises can be caught -and handled using [`promise.catch(...)`][] and rejections are propagated through +and handled using [`promise.catch()`][] and rejections are propagated through a promise chain. This event is useful for detecting and keeping track of promises that were rejected whose rejections were not handled yet. This event is emitted with the following arguments: @@ -182,7 +187,7 @@ var resource = new SomeResource(); In cases like this, you may not want to track the rejection as a developer error like you would for other `'unhandledRejection'` events. To address -this, you can either attach a dummy `.catch(() => { })` handler to +this, you can either attach a dummy [`.catch(() => { })`][`promise.catch()`] handler to `resource.loaded`, preventing the `'unhandledRejection'` event from being emitted, or you can use the [`'rejectionHandled'`][] event. @@ -307,7 +312,7 @@ operations are pending. The following status codes are used in other cases: * `1` **Uncaught Fatal Exception** - There was an uncaught exception, - and it was not handled by a domain or an `'uncaughtException'` event + and it was not handled by a domain or an [`'uncaughtException'`][] event handler. * `2` - Unused (reserved by Bash for builtin misuse) * `3` **Internal JavaScript Parse Error** - The JavaScript source code @@ -327,7 +332,7 @@ cases: * `7` **Internal Exception Handler Run-Time Failure** - There was an uncaught exception, and the internal fatal exception handler function itself threw an error while attempting to handle it. This - can happen, for example, if a `process.on('uncaughtException')` or + can happen, for example, if a [`'uncaughtException'`][] or `domain.on('error')` handler throws an error. * `8` - Unused. In previous versions of Node.js, exit code 8 sometimes indicated an uncaught exception. @@ -397,7 +402,7 @@ Note: - `SIGSTOP` cannot have a listener installed. Note that Windows does not support sending Signals, but Node.js offers some -emulation with `process.kill()`, and `child_process.kill()`. Sending signal `0` +emulation with [`process.kill()`][], and [`ChildProcess.kill()`][]. Sending signal `0` can be used to test for the existence of a process. Sending `SIGINT`, `SIGTERM`, and `SIGKILL` cause the unconditional termination of the target process. @@ -495,9 +500,9 @@ the value of `process.config`.* ## process.connected -* {Boolean} Set to false after `process.disconnect()` is called +* {Boolean} Set to `false` after `process.disconnect()` is called -If `process.connected` is false, it is no longer possible to send messages. +If `process.connected` is `false`, it is no longer possible to send messages. ## process.cwd() @@ -665,7 +670,7 @@ emitMyWarning(); This is the set of Node.js-specific command line options from the executable that started the process. These options do not show up in -`process.argv`, and do not include the Node.js executable, the name of +[`process.argv`][], and do not include the Node.js executable, the name of the script, or any options following the script name. These options are useful in order to spawn child processes with the same execution environment as the parent. @@ -719,7 +724,7 @@ A number which will be the process exit code, when the process either exits gracefully, or is exited via [`process.exit()`][] without specifying a code. -Specifying a code to `process.exit(code)` will override any previous +Specifying a code to [`process.exit(code)`][`process.exit()`] will override any previous setting of `process.exitCode`. @@ -837,7 +842,7 @@ console.log(process.getgroups()); // [ 27, 30, 46, 1000 ] Send a signal to a process. `pid` is the process id and `signal` is the string describing the signal to send. Signal names are strings like -`SIGINT` or `SIGHUP`. If omitted, the signal will be `SIGTERM`. +`'SIGINT'` or `'SIGHUP'`. If omitted, the signal will be `'SIGTERM'`. See [Signal Events][] and kill(2) for more information. Will throw an error if target does not exist, and as a special case, a signal @@ -869,11 +874,11 @@ Note: When SIGUSR1 is received by Node.js it starts the debugger, see ## process.mainModule Alternate way to retrieve [`require.main`][]. The difference is that if the main -module changes at runtime, `require.main` might still refer to the original main +module changes at runtime, [`require.main`][] might still refer to the original main module in modules that were required before the change occurred. Generally it's safe to assume that the two refer to the same module. -As with `require.main`, it will be `undefined` if there was no entry script. +As with [`require.main`][], it will be `undefined` if there was no entry script. ## process.memoryUsage() @@ -1043,7 +1048,7 @@ relied upon to exist. When Node.js is spawned with an IPC channel attached, it can send messages to its parent process using `process.send()`. Each will be received as a -[`'message'`][] event on the parent's `ChildProcess` object. +[`'message'`][] event on the parent's [`ChildProcess`][] object. *Note: this function uses [`JSON.stringify()`][] internally to serialize the `message`.* @@ -1055,7 +1060,7 @@ Note: this function is only available on POSIX platforms (i.e. not Windows, Android) Sets the effective group identity of the process. (See setegid(2).) -This accepts either a numerical ID or a groupname string. If a groupname +This accepts either a numerical ID or a group name string. If a group name is specified, this method blocks while resolving it to a numerical ID. ```js @@ -1099,7 +1104,7 @@ Note: this function is only available on POSIX platforms (i.e. not Windows, Android) Sets the group identity of the process. (See setgid(2).) This accepts either -a numerical ID or a groupname string. If a groupname is specified, this method +a numerical ID or a group name string. If a group name is specified, this method blocks while resolving it to a numerical ID. ```js @@ -1152,7 +1157,7 @@ if (process.getuid && process.setuid) { A writable stream to stderr (on fd `2`). `process.stderr` and `process.stdout` are unlike other streams in Node.js in -that they cannot be closed (`end()` will throw), they never emit the `finish` +that they cannot be closed ([`end()`][] will throw), they never emit the [`'finish'`][] event and that writes can block when output is redirected to a file (although disks are fast and operating systems normally employ write-back caching so it should be a very rare occurrence indeed.) @@ -1202,7 +1207,7 @@ console.log = (msg) => { ``` `process.stderr` and `process.stdout` are unlike other streams in Node.js in -that they cannot be closed (`end()` will throw), they never emit the `'finish'` +that they cannot be closed ([`end()`][] will throw), they never emit the [`'finish'`][] event and that writes can block when output is redirected to a file (although disks are fast and operating systems normally employ write-back caching so it should be a very rare occurrence indeed.) @@ -1287,21 +1292,30 @@ Will print something like: openssl: '1.0.1k' } ``` +[`'finish'`]: stream.html#stream_event_finish [`'message'`]: child_process.html#child_process_event_message +[`'rejectionHandled'`]: #process_event_rejectionhandled +[`'uncaughtException'`]: #process_event_uncaughtexception [`ChildProcess.disconnect()`]: child_process.html#child_process_child_disconnect +[`ChildProcess.kill()`]: child_process.html#child_process_child_kill_signal [`ChildProcess.send()`]: child_process.html#child_process_child_send_message_sendhandle_options_callback +[`ChildProcess`]: child_process.html#child_process_class_childprocess +[`end()`]: stream.html#stream_writable_end_chunk_encoding_callback [`Error`]: errors.html#errors_class_error [`EventEmitter`]: events.html#events_class_eventemitter +[`EventEmitter`]: events.html#events_class_events_eventemitter +[`JSON.stringify()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify [`net.Server`]: net.html#net_class_net_server [`net.Socket`]: net.html#net_class_net_socket +[`process.argv`]: #process_process_argv [`process.exit()`]: #process_process_exit_code -[`promise.catch(...)`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch -[`'rejectionHandled'`]: #process_event_rejectionhandled +[`process.kill()`]: #process_process_kill_pid_signal +[`promise.catch()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch [`require.main`]: modules.html#modules_accessing_the_main_module [`setTimeout(fn, 0)`]: timers.html#timers_settimeout_callback_delay_arg +[child_process `'disconnect'` event]: child_process.html#child_process_event_disconnect +[process_emit_warning]: #process_emitwarning_warning_name_ctor +[process_warning]: #process_event_warning [Signal Events]: #process_signal_events [Stream compatibility]: stream.html#stream_compatibility_with_older_node_js_versions [the tty docs]: tty.html#tty_tty -[`JSON.stringify()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify -[process_warning]: #process_event_warning -[process_emit_warning]: #process_process_emitwarning_warning_name_ctor