In-depth understanding of the process object in nodejs

console.log(process === global.process);//true

console.log(process);

console.log(process.argv);//[ 'D:\\nodejs\\node.exe', 'D:\\project\\main.js' ]

console.log(process.execArgv);

console.log(process.execPath);//D:\nodejs\node.exe

/*
{ PROCESSOR_ARCHITEW6432: 'AMD64',
  PROCESSOR_LEVEL: '6',
  COMMONPROGRAMW6432: 'C:\\Program Files\\Common Files',
  PROMPT: '$P$G',
  PSMODULEPATH: 'C:\\WINDOWS\\system32\\WindowsPowerShell\\v1.0\\Modules\\',
  APPDATA: 'C:\\Users\\Administrator\\AppData\\Roaming',
  COMPUTERNAME: 'BAI',
  COMSPEC: 'C:\\WINDOWS\\system32\\cmd.exe',
  FPS_BROWSER_APP_PROFILE_STRING: 'Internet Explorer',
  USERPROFILE: 'C:\\Users\\Administrator',
  HOMEDRIVE: 'C:',
  USERNAME: 'Administrator',
  FP_NO_HOST_CHECK: 'NO',
  WINDIR: 'C:\\WINDOWS',
  PROCESSOR_REVISION: '3c03',
  FPS_BROWSER_USER_PROFILE_STRING: 'Default',
  TMP: 'C:\\Users\\ADMINI~1\\AppData\\Local\\Temp',
  _DFX_INSTALL_UNSIGNED_DRIVER: '1',
  PUBLIC: 'C:\\Users\\Public',
  'COMMONPROGRAMFILES(X86)': 'C:\\Program Files (x86)\\Common Files',
  NUMBER_OF_PROCESSORS: '8',
  SYSTEMROOT: 'C:\\WINDOWS',
  TEMP: 'C:\\Users\\ADMINI~1\\AppData\\Local\\Temp',
  PROCESSOR_ARCHITECTURE: 'x86',
  LOCALAPPDATA: 'C:\\Users\\Administrator\\AppData\\Local',
  VISUALSVN_SERVER: 'D:\\soft\\svn1\\',
  COMMONPROGRAMFILES: 'C:\\Program Files (x86)\\Common Files',
  NODE_PATH: 'D:\\nodejs\\node_modules',
  ALLUSERSPROFILE: 'C:\\ProgramData',
  HOMEPATH: '\\Users\\Administrator',
  USERDOMAIN: 'BAI',
  WINDOWS_TRACING_LOGFILE: 'C:\\BVTBin\\Tests\\installpackage\\csilogfile.log',
  PROGRAMFILES: 'C:\\Program Files (x86)',
  VBOX_MSI_INSTALL_PATH: 'D:\\soft\\va\\',
  SYSTEMDRIVE: 'C:',
  PATH: 'C:\\WINDOWS\\system32;C:\\WINDOWS;C:\\WINDOWS\\System32\\Wbem;C:\\WINDOWS\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\syswow64;C:\\Program Files (x86)\\Microsoft SQL Server\\80\\Tools\\Binn\\;d:\\;D:\\nodejs;D:\\nodejs\\;D:\\Git\\cmd;D:\\soft\\svn1\\bin;D:\\soft\\svn2\\bin;C:\\Ruby23\\bin;D:\\soft\\Sublime Text 3\\less.js-windows-master;C:\\Users\\Administrator\\AppData\\Local\\Microsoft\\WindowsApps;D:\\wamp\\bin\\mysql\\mysql5.6.17\\bin;C:\\Users\\Administrator\\AppData\\Roaming\\npm',
  PROGRAMW6432: 'C:\\Program Files',
  PATHEXT: '.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC',
  WINDOWS_TRACING_FLAGS: '3',
  PROCESSOR_IDENTIFIER: 'Intel64 Family 6 Model 60 Stepping 3, GenuineIntel',
  USERDOMAIN_ROAMINGPROFILE: 'BAI',
  LOGONSERVER: '\\\\BAI',
  PROGRAMDATA: 'C:\\ProgramData',
  SESSIONNAME: 'Console',
  'PROGRAMFILES(X86)': 'C:\\Program Files (x86)',
  OS: 'Windows_NT' }
 */
console.log(process.env);

console.log(process.env.USERNAME);//Administrator

console.log(process.version);//v6.9.2

/*
{ http_parser: '2.7.0',
  node: '6.9.2',
  v8: '5.1.281.88',
  uv: '1.9.1',
  zlib: '1.2.8',
  ares: '1.10.1-DEV',
  icu: '57.1',
  modules: '48',
  openssl: '1.0.2j' }
 */
console.log(process.versions);

setInterval(function(){
    console.log(process.pid);//11204}, 5000);

console.log(process.arch);//ia32

console.log(process.platform); //win32

console.log(process.cwd());//D:\project

console.log(process.cwd());//D:\projecttry {
  process.chdir('./dist');
  console.log(process.cwd());//D:\project\dist}catch (err) {
  console.log('chdir: ' + err);
}

console.log(process.memoryUsage()); //{ rss: 18894848, heapTotal: 7274496, heapUsed: 3263160 }

console.log(process.uptime());//0.139
var arr = new Array(200000000);
var s = arr.join(',');
console.log(process.uptime());//0.212

var t1 = process.hrtime();
var arr = new Array(200000000),
    s = arr.join(',');
var t2 = process.hrtime();
//处理数组共花费了0秒，详细为64756416纳秒
console.log('处理数组共花费了%d秒，详细为%d纳秒', (t2[0] - t1[0]), (t2[1] - t1[1]));

console.log(process.pid);//19960
process.kill(process.pid, 'SIGTERM');
console.log(process.pid);//''

process.abort();
console.log('在输出这句话之前就退出了');

process.exit(); //[Finished in 0.2s]

process.exit(1); //[Finished in 0.2s with exit code 1]

1 未捕获的致命异常(Uncaught Fatal Exception) - There was an uncaught exception, and it was not handled by a domain or an uncaughtException event handler.
2 - 未使用(Unused) (reserved by Bash for builtin misuse)
3 解析错误(Internal JavaScript Parse Error) - The JavaScript source code internal in Node's bootstrapping process caused a parse error. This is extremely rare, and generally can only happen during development of Node itself.
4 评估失败(Internal JavaScript Evaluation Failure) - The JavaScript source code internal in Node's bootstrapping process failed to return a function value when evaluated. This is extremely rare, and generally can only happen during development of Node itself.
5 致命错误(Fatal Error) - There was a fatal unrecoverable error in V8. Typically a message will be printed to stderr with the prefix FATAL ERROR.
6 未正确的异常处理(Non-function Internal Exception Handler) - There was an uncaught exception, but the internal fatal exception handler function was somehow set to a non-function, and could not be called.
7 异常处理函数运行时失败(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 domain.on('error') handler throws an error.
8 - 未使用(Unused). In previous versions of Node, exit code 8 sometimes indicated an uncaught exception.
9 - 无效的参数(Invalid Argument) - Either an unknown option was specified, or an option requiring a value was provided without a value.
10 运行时失败(Internal JavaScript Run-Time Failure) - The JavaScript source code internal in Node's bootstrapping process threw an error when the bootstrapping function was called. This is extremely rare, and generally can only happen during development of Node itself.
12 无效的调试参数(Invalid Debug Argument) - The --debug and/or --debug-brk options were set, but an invalid port number was chosen.
>128 信号退出(Signal Exits) - If Node receives a fatal signal such as SIGKILL or SIGHUP, then its exit code will be 128 plus the value of the signal code. This is a standard Unix practice, since exit codes are defined to be 7-bit integers, and signal exits set the high-order bit, and then contain the value of the signal code.

process.exitCode = 4;
process.exit();//[Finished in 0.2s with exit code 4]

process.exitCode = 4;
process.exit(2);//[Finished in 0.2s with exit code 2]

/*这是一行数据
这是第二行数据 */process.stdout.write('这是一行数据\n这是第二行数据');

//输出一行标准错误流，效果跟stdout没差[Finished in 0.2s]
process.stderr.write('输出一行标准错误流，效果跟stdout没差');

process.stdin.resume();
var a,b;
process.stdout.write('请输入a的值: ');
process.stdin.on('data',function(data){
    if(a == undefined){
        a = Number(data);
        process.stdout.write('请输入b的值: ');
    }else{    
        b = Number(data);
        process.stdout.write('结果是: ' + (a+b));
        process.exit();
    }

    
})

/*
1
退出前执行
 */
process.on('exit', function() {
    // 设置一个延迟执行
    setTimeout(function() {
        console.log('主事件循环已停止，所以不会执行');
    }, 0);
    console.log('退出前执行');
});
setTimeout(function() {
    console.log('1');
}, 500);

//捕获到一个异常
process.on('uncaughtException', function() {
    console.log('捕获到一个异常');
});
var a = '123';
a.a(); //触发异常事件
console.log('这句话不会显示出来');

process.on('SIGINT', function() {
    console.log('收到 SIGINT 信号。');
});
console.log('试着按下 ctrl + C');
setTimeout(function() {
    console.log('end');
}, 50000);

function foo() {
  　　console.error('foo');
}
 
process.nextTick(foo);
console.error('bar');/*bar
foo*/

setTimeout(foo, 0);
console.log('bar');

var http = require('http');
function compute() {
　　　　// performs complicated calculations continuously
　　　　process.nextTick(compute);
}
http.createServer(function(req, res) {
 　　　　res.writeHead(200, {'Content-Type': 'text/plain'});
 　　　　res.end('Hello World');
}).listen(5000, '127.0.0.1');
compute();