标签：rmi proc .exe htm return message 需要 module run
child_process 这个模块可以生成一个子进程。nodejs提供了好几个API,本质上都是调用child_process.spawn()：
1 const spawn = require(‘child_process‘).spawn; 2 const ls = spawn(‘ls‘, [‘-lh‘, ‘/usr‘]); 3 4 ls.stdout.on(‘data‘, (data) => { 5 console.log(`stdout: ${data}`); 6 }); 7 8 ls.stderr.on(‘data‘, (data) => { 9 console.log(`stderr: ${data}`); 10 }); 11 12 ls.on(‘close‘, (code) => { 13 console.log(`child process exited with code ${code}`); 14 });
默认情况下：stdin, stdout and stderr 这3个管道会链接在父进程和子进程之间！这使得父子进程数据流的交互畅通无阻。注意：有些程序自身内部利用了I/0
Buffer,但是这并不影响Node.js. 它只是意味着父进程发送数据给子进程不能马上消耗掉而已。
Nodejs为了方便大家使用，提供了很多同步与异步的方法，本文只介绍异步的！异步的优点就是不会阻塞Nodejs的事件循环。
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 it spawns the command directly without first spawning a shell.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.spawn(), child_process.fork(), child_process.exec(), and child_process.execFile()
都会返回一个ChildProcess 实例。ChildProcess 实现了NodejsEventEmitter的 API,允许父进程注册监听函数，在子进程的生命周期内发生指定事件的时候调用。
child_process.exec() and child_process.execFile()还额外提供了callback选项，当子进程终止的时候调用！
.bat and .cmd files on Windowschild_process.exec() and child_process.execFile()最大的区别无疑是基于的平台不同！
在 Unix-type 这样类型的操作系统上 (Unix, Linux, OSX) ,child_process.execFile() 跑起来更高效，因为他不需要生成一个shell.
然后在Windows上，.bat and .cmd文件是无法离开终端独立执行的,玩Windows的同志只能用child_process.exec()来执行批处理文件。
或者说利用child_process.spawn() 配置项里设置shell.
或者说利用生成一个cmd.exe ，然后传 .bat or .cmd文件名作为参数。这里关键了。一定要带上 /? 不然在你无法生成一个新的shell实例。
1 // On Windows Only ... 2 const spawn = require(‘child_process‘).spawn; 3 const bat = spawn(‘cmd.exe‘, [‘/c‘, ‘my.bat‘]); 4 5 bat.stdout.on(‘data‘, (data) => { 6 console.log(data); 7 }); 8 9 bat.stderr.on(‘data‘, (data) => { 10 console.log(data); 11 }); 12 13 bat.on(‘exit‘, (code) => { 14 console.log(`Child exited with code ${code}`); 15 }); 16 17 // OR... 18 const exec = require(‘child_process‘).exec; 19 exec(‘my.bat‘, (err, stdout, stderr) => { 20 if (err) { 21 console.error(err); 22 return; 23 } 24 console.log(stdout); 25 }); 26 27 // Script with spaces in the filename: 28 const bat = spawn(‘"my script.cmd"‘, [‘a‘, ‘b‘], { shell:true }); 29 // or: 30 exec(‘"my script.cmd" a b‘, (err, stdout, stderr) => { 31 // ... 32 });
command <String> The command to run, with space-separated argumentsoptions <Object>
cwd <String> Current working directory of the child processenv <Object> Environment key-value pairsencoding <String> (Default: ‘utf8‘)shell <String> Shell to execute the command with (Default: ‘/bin/sh‘ on UNIX, ‘cmd.exe‘ on Windows, The shell should understand the -c switch on UNIX or /d /s /c on Windows. On Windows, command line parsing should be compatible with cmd.exe.)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‘)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
1 { 2 encoding: ‘utf8‘, 3 timeout: 0, 4 maxBuffer: 200*1024, 5 killSignal: ‘SIGTERM‘, 6 cwd: null, 7 env: null 8 }
注意回调里的3个参数，如果指定了encoding，那就是String，不然就是buffer。
timeout（如果大于0） 是为了规定子进程的执行时间，如果超过了，这时候就会用到 killSignal 属性了，默认父进程发送的是 ‘SIGTERM‘。
不同于exec(3) POSIX，child_process.exec() 是不会取代已经存在的进程的，使用shell来执行命令。
file <String> The name or path of the executable file to runargs <Array> List of string argumentsoptions <Object>
cwd <String> Current working directory of the child processenv <Object> Environment key-value pairsencoding <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‘)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
child_process.execFile()和child_process.exec()很像，除了 child_process.execFile() 执行的时候不会生成新的shell，这个指定的file将会被执行作为新进程。
这一点比child_process.exec() 更有效率。
这里部分一点：
开始学习child_process模块的时候以为spawn可以直接运行命令, 后来发现这是一个小陷阱就拿出来和大家分享一下.
先说下我碰到的情况由于在windos下写的所以根据docs上的例子我就写出了这么一句代码:"require(“child_process”).spawn(“dir”), 这么写是会有错误的,用error接受到的数据是没有此文件. 而用exec就不会有问题,于是得到了以前的猜想.
大家都知道在linux下, ls命令对应的是一个文件, 而在windows下是做为cmd的内置命令的. 所以像我那样写是会报错.
于是我查看了child_process的源码发现spawn是这样定义的var spawn = exports.spawn = function(file, args, options); 也就是说他传入的应该是一个文件, 例如ping, cmd等. 而exec的源码中有一段这样的代码:
if (process.platform === ‘win32‘) {
file = ‘cmd.exe‘;
args = [‘/s‘, ‘/c‘, ‘"‘ + command + ‘"‘];
// Make a shallow copy before patching so we don‘t clobber the user‘s
// options object.
options = util._extend({}, options);
options.windowsVerbatimArguments = true;
} else {
file = ‘/bin/sh‘;
args = [‘-c‘, command];
}所以想使用内置命令可以直接使用exec或者把spawn改成spawn(“cmd.exe”,["\s", “\c”, “dir”]);
总结起来就是spawn是调用一个文件! 不要被docs上的child_process.spawn(command, [args], [options])中的command给骗了
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在windows上，设置options.detached 为 true，可以保证父进程退出的时候，子进程还可以运行，子进程拥有自己的console窗口，一旦启动，就不可能停止。
非windows的话，设置options.detached 为 true，子进程将会新进程的控制者，不管父子进程有没有设置detached ，子进程都可以在父进程退出后保存运行！
默认情况下 ，父进程需要等子进程运行完毕才离开，但是我们可以调用child.unref() 来避免发生！这样允许父进程和子进程独立开来，除非他们建立了IPC信道。
看一眼为什么：
针对handle而言，判断loop是否存活只要看loop->active_handles是否大于0，大于0则存活。
具体代码参看 https://github.com/libuv/libuv/blob/v1.x/src/uv-common.h
uv__handle_init, uv__handle_start, uv__handle_stop, uv__handle_ref, uv__handle_unref
比较下面几种情况，可能会有利于理解unref的作用。
第一种
var timer1 = setTimeout(function(){
console.log(new Date, 1);
}, 1000);
// setTimeout=>uv_timer_start(timer1) active_handles = 1
var timer2 = setInterval(function(){
console.log(new Date, 2);
}, 1000);
// setInterval=>uv_timer_start(timer2) active_handles = 2
// 1: ative_handles > 0 => loop()
// timer1 timeout => uv_timer_stop(timer1) active_handles = 1 => callback()
// timer2 timeout => uv_timer_stop(timer2) active_handles = 0 => callback() => uv_timer_start(timer2) active_handles = 1
// 2: active_handles > 0 => loop()
// timer2 timeout => uv_timer_stop(timer2) active_handles = 0 => callback() => uv_timer_start(timer2) active_handles = 1
// goto 2第二种
var timer1 = setTimeout(function(){
console.log(new Date, 1);
}, 1000);
// setTimeout=>uv_timer_start(timer1) active_handles = 1
var timer2 = setInterval(function(){
console.log(new Date, 2);
}, 1000);
// setInterval=>uv_timer_start(timer2) active_handles = 2
timer2.unref();
// uv_unref(timer2) active_handles = 1
// ative_handles > 0 => loop()
// timer1 timeout => uv_timer_stop(timer1) active_handles = 0 => callback()
// timer2 timeout => uv_timer_stop(timer2) active_handles = 0 => callback() => uv_timer_start(timer2) active_handles = 0
// active_handles == 0 => exit_process第三种
var timer1 = setInterval(function(){
console.log(new Date, 1);
}, 1000);
// setInterval=>uv_timer_start(timer1) active_handles = 1
var timer2 = setInterval(function(){
console.log(new Date, 2);
}, 1000);
// setInterval=>uv_timer_start(timer2) active_handles = 2
// 1: ative_handles > 0 => loop()
// timer1 timeout => uv_timer_stop(timer1) active_handles = 1 => callback() => uv_timer_start(timer1) active_handles = 2
// timer2 timeout => uv_timer_stop(timer2) active_handles = 1 => callback() => uv_timer_start(timer2) active_handles = 2
// goto 1第四种
var timer1 = setInterval(function(){
console.log(new Date, 1);
}, 1000);
// setInterval=>uv_timer_start(timer1) active_handles = 1
var timer2 = setInterval(function(){
console.log(new Date, 2);
}, 1000);
// setInterval=>uv_timer_start(timer2) active_handles = 2
timer2.unref()
// uv_unref(timer2) active_handles = 1
// 1: ative_handles > 0 => loop()
// timer1 timeout => uv_timer_stop(timer1) active_handles = 0 => callback() => uv_timer_start(timer1) active_handles = 1
// timer2 timeout => uv_timer_stop(timer2) active_handles = 1 => callback() => uv_timer_start(timer2) active_handles = 1
// goto 1第五种
var timer1 = setInterval(function(){
console.log(new Date, 1);
}, 1000);
// setInterval=>uv_timer_start(timer1) active_handles = 1
timer1.unref()
// uv_unref(timer1) active_handles = 0
var timer2 = setInterval(function(){
console.log(new Date, 2);
}, 1000);
// setInterval=>uv_timer_start(timer2) active_handles = 1
timer2.unref()
// uv_unref(timer2) active_handles = 0
// ative_handles == 0 => exit process
--------------------------------------------------------------------------
标签：rmi proc .exe htm return message 需要 module run
原文地址：http://www.cnblogs.com/huenchao/p/6216240.html
