node.jsで標準出力から一行ずつ読み込んでファイルに書きこむ例

stream_example.js

var fs = require('fs');
var buffer = '';
var out = fs.createWriteStream('test.txt', {
    encoding: 'utf8',
    mode: 0644,
});

process.stdin.resume();

process.stdin.setEncoding('utf8');

process.stdin.on('data', function (chunk) {
    var parts = chunk.split(/\n|\r\n/g);

    if (buffer.length > 0) {
        parts[0] = buffer + parts[0];
    }

    for (var i = 0, l = parts.length - 1; i < l; i++) {
        if (!out.write(parts[i] + '\n')) {
            process.stdin.pause();
        }
    }

    buffer = parts[parts.length - 1];
});

process.stdin.on('end', function (data) {
    if (buffer.length > 0) {
        out.end(buffer + '\n');
    }

    console.log('end');
});

out.on('drain', function() {
    process.stdin.resume();
});