Node.js readline 逐行读取、写入文件内容的示例
Sodino 人气:0本文介绍了运用readline逐行读取的两种实现,分享给大家,具体如下:
什么是Readline
Readline是Node.js里实现标准输入输出的封装好的模块,通过这个模块我们可以以逐行的方式读取数据流。使用require(“readline”)可以引用模块。
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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