【node.js】'readline' 逐行读取、写入文件内容

运用readline逐行读取，在写入行数数据时用两种思路实现。

效果图如下：
左边1.log 为源文件
右边1.readline.log为复制后的文件
下边为命令行输出

实现方式一:

var readline = require('readline');
var fs = require('fs');
var os = require('os');

var fReadName = './1.log';
var fWriteName = './1.readline.log';
var fRead = fs.createReadStream(fReadName);
var fWrite = fs.createWriteStream(fWriteName);


var objReadline = readline.createInterface({
	input: fRead,
// 这是另一种复制方式，这样on('line')里就不必再调用fWrite.write(line)，当只是纯粹复制文件时推荐使用
// 但文件末尾会多算一次index计数   sodino.com
//  output: fWrite, 
//  terminal: true
});


var index = 1;
objReadline.on('line', (line)=>{
	var tmp = 'line' + index.toString() + ':' + line;
	fWrite.write(tmp + os.EOL); // 下一行
	console.log(index, line);
	index ++;
});

objReadline.on('close', ()=>{
	console.log('readline close...');
});

实现方式二:

var readline = require('readline');
var fs = require('fs');
var os = require('os');

var fReadName = './1.log';
var fWriteName = './1.readline.log';
var fRead = fs.createReadStream(fReadName);
var fWrite = fs.createWriteStream(fWriteName);

var enableWriteIndex = true;
fRead.on('end', ()=>{
	console.log('end');
	enableWriteIndex = false;
});

var objReadline = readline.createInterface({
	input: fRead,
  	output: fWrite, 
	terminal: true
});


var index = 1;
fWrite.write('line' + index.toString() +':');
objReadline.on('line', (line)=>{
	console.log(index, line);
	if (enableWriteIndex) {
		// 由于readline::output是先写入后调用的on('line')事件，
		// 所以已经读取文件完毕时就不需要再写行号了... sodino.com
		index ++;
		var tmp = 'line' + index.toString() + ':';
		fWrite.write(tmp);		
	}
});



objReadline.on('close', ()=>{
	console.log('readline close...');
});

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