Node.js生成过程如何使用stdout seperatley的每一行在函数中使用

Question

okay so i have my nodejs script below

var app = require('express')();
var server = require('http').createServer(app);
var bin = "casperjs";
var args = ['Backend.js'];
var io = require('socket.io').listen(server);
server.listen(process.env.PORT);

app.get('/', function (req, res) {
    res.sendfile(__dirname + '/client/index.html');
});

io.sockets.on('connection', function (socket) {
    console.log("socket connection incoming");
});

var spawn = require('child_process').spawn,
child = spawn(bin, args);
child.stdin.setEncoding = 'utf-8';

child.stdout.on('data', function (data) {
    when (data = "Well Hello1") {
        console.log("Working1");
    }
    if (data = "Well Hello2") {
        console.log("Working2");
    }
    if (data = "Well Hello.") {
        console.log("Working");
    }
});

The problems is my if statements are not handled correctly.

I have figured out i need to handle the stdout line by line and not as a stream can any one show me a solution please

Answer 1

You might find that using the event-stream module makes this much easier.

You can then do something like this:

var es = require('event-stream');

es.pipeline(
    child.stdout,
    es.split(),
    es.map(function (line) {
        if (line === 'Well Hello1') {
            console.log("Working1");
        }
    })
);

You'll need to npm install event-stream first.

Here's a new version of your full script:

var app = require('express')();
var server = require('http').createServer(app);
var bin = "casperjs";
var args = ['Backend.js'];
var io = require('socket.io').listen(server);
server.listen(process.env.PORT);

app.get('/', function (req, res) {
    res.sendfile(__dirname + '/client/index.html');
});

io.sockets.on('connection', function (socket) {
    console.log("socket connection incoming");
});

var spawn = require('child_process').spawn,
child = spawn(bin, args);
child.stdin.setEncoding = 'utf-8';

var es = require('event-stream');

es.pipeline(
    child.stdout,
    es.split(),
    es.map(function (line) {
        if (line === 'Well Hello1') {
            console.log("Working1");
        }
    })
);

EDIT : A simple a script that demonstrates spawning /bin/cat , setting up a pipeline to split and then log what is written line-by-line, and sometimes write back to child.stdin . If you run this script it will hang waiting for input to cat , but you will see what is output and you can play with it easily:

var es = require('event-stream');
var spawn = require('child_process').spawn;

var child = spawn('/bin/cat');
var count = 0;

var stream = es.pipeline(
    child.stdout,
    es.split(),
    es.map(function (line) {
        console.log("es.map(" + line + "):");
        if (count < 3) {
            child.stdin.write("Hello(" + count + ")\n");
        }
        count++;
    })
);

child.stdin.write("Testing1\nTesting2");
child.stdin.write("Testing3\nTesting4\n");
child.stdin.write("Testing5\nTesting6\n");

stream.on('data', function (line) {
    console.log(line);
    if (line === '') {
        console.log('end');
        stream.end();
    }
});

Answer 2

Here's a simpler example, for ping:

var split = require('split');
var spawn = require('child_process').spawn;

var child = spawn('ping', ['www.google.com']);

child.stdout.pipe(split()).on('data', function (line) {
    console.log('**' + line + '**');
});