Node.js和其他语言一样,也有文件操作。先不说node.js中的文件操作,其他语言的文件操作一般也都是有打开、关闭、读、写、文件信息、新建删除目录、删除文件、检测文件路径等。在node.js中也是一样,也都是这些功能,可能就是api与其他语言不太一样。

一、同步、异步打开关闭

/** * Created by Administrator on 2016/3/21. */ var fs=require("fs"); //同步读 fs.openSync = function(path, flags, mode) //模块fs.js文件中如上面定义的openSync 函数3个参数 //.1.path 文件路径 //2.flags 打开文件的模式 //3.model 设置文件访问模式 //fd文件描述 var fd=fs.openSync("data/openClose.txt",'w'); //fs.closeSync = function(fd) fs.closeSync(fd); //异步读写 //fs.open = function(path, flags, mode, callback_) //fs.close = function(fd, callback) fs.open("data/openColse1.txt",'w',function(err,fd) { if (!err) { fs.close(fd,function(){ console.log("closed"); }); } });

其中的flags其他语言也会有.其实主要分3部分 r、w、a.和C中的差不多。

1.r —— 以只读方式打开文件，数据流的初始位置在文件开始

2.r+ —— 以可读写方式打开文件，数据流的初始位置在文件开始

3.w ——如果文件存在，则将文件长度清0，即该文件内容会丢失。如果不存在，则尝试创建它。数据流的初始位置在文件开始

4.w+ —— 以可读写方式打开文件，如果文件不存在，则尝试创建它，如果文件存在，则将文件长度清0，即该文件内容会丢失。数据流的初始位置在文件开始

5.a —— 以只写方式打开文件，如果文件不存在，则尝试创建它，数据流的初始位置在文件末尾，随后的每次写操作都会将数据追加到文件后面。

6.a+ ——以可读写方式打开文件，如果文件不存在，则尝试创建它，数据流的初始位置在文件末尾，随后的每次写操作都会将数据追加到文件后面。

二、读写

1.简单文件读写

/** * Created by Administrator on 2016/3/21. */ var fs = require('fs'); var config = { maxFiles: 20, maxConnections: 15, rootPath: "/webroot" }; var configTxt = JSON.stringify(config); var options = {encoding:'utf8', flag:'w'}; //options 定义字符串编码 打开文件使用的模式 标志的encoding、mode、flag属性 可选 //异步 //fs.writeFile = function(path, data, options, callback_) //同步 //fs.writeFileSync = function(path, data, options) fs.writeFile('data/config.txt', configTxt, options, function(err){ if (err){ console.log("Config Write Failed."); } else { console.log("Config Saved."); readFile(); } }); function readFile() { var fs = require('fs'); var options = {encoding:'utf8', flag:'r'}; //异步 //fs.readFile = function(path, options, callback_) //同步 //fs.readFileSync = function(path, options) fs.readFile('data/config.txt', options, function(err, data){ if (err){ console.log("Failed to open Config File."); } else { console.log("Config Loaded."); var config = JSON.parse(data); console.log("Max Files: " + config.maxFiles); console.log("Max Connections: " + config.maxConnections); console.log("Root Path: " + config.rootPath); } }); }

"C:Program Files (x86)JetBrainsWebStorm 11.0.3binrunnerw.exe" F:nodejsnode.exe SimpleReadWrite.js Config Saved. Config Loaded. Max Files: 20 Max Connections: 15 Root Path: /webroot Process finished with exit code 0

2.同步读写

/** * Created by Administrator on 2016/3/21. */ var fs = require('fs'); var veggieTray = ['carrots', 'celery', 'olives']; fd = fs.openSync('data/veggie.txt', 'w'); while (veggieTray.length){ veggie = veggieTray.pop() + " "; //系统api //fd 文件描述 第二个参数是被写入的String或Buffer // offset是第二个参数开始读的索引 null是表示当前索引 //length 写入的字节数 null一直写到数据缓冲区末尾 //position 指定在文件中开始写入的位置 null 文件当前位置 // fs.writeSync(fd, buffer, offset, length[, position]); // fs.writeSync(fd, string[, position[, encoding]]); //fs.writeSync = function(fd, buffer, offset, length, position) var bytes = fs.writeSync(fd, veggie, null, null); console.log("Wrote %s %dbytes", veggie, bytes); } fs.closeSync(fd); var fs = require('fs'); fd = fs.openSync('data/veggie.txt', 'r'); var veggies = ""; do { var buf = new Buffer(5); buf.fill(); //fs.readSync = function(fd, buffer, offset, length, position) var bytes = fs.readSync(fd, buf, null, 5); console.log("read %dbytes", bytes); veggies += buf.toString(); } while (bytes > 0); fs.closeSync(fd); console.log("Veggies: " + veggies);

"C:Program Files (x86)JetBrainsWebStorm 11.0.3binrunnerw.exe" F:nodejsnode.exe syncReadWrite.js Wrote olives 7bytes Wrote celery 7bytes Wrote carrots 8bytes read 5bytes read 5bytes read 5bytes read 5bytes read 2bytes read 0bytes Veggies: olives celery carrots Process finished with exit code 0

3.异步读写 和同步读写的参数差不多就是多了callback

/** * Created by Administrator on 2016/3/21. */ var fs = require('fs'); var fruitBowl = ['apple', 'orange', 'banana', 'grapes']; function writeFruit(fd){ if (fruitBowl.length){ var fruit = fruitBowl.pop() + " "; // fs.write(fd, buffer, offset, length[, position], callback); // fs.write(fd, string[, position[, encoding]], callback); // fs.write = function(fd, buffer, offset, length, position, callback) fs.write(fd, fruit, null, null, function(err, bytes){ if (err){ console.log("File Write Failed."); } else { console.log("Wrote: %s %dbytes", fruit, bytes); writeFruit(fd); } }); } else { fs.close(fd); ayncRead(); } } fs.open('data/fruit.txt', 'w', function(err, fd){ writeFruit(fd); }); function ayncRead() { var fs = require('fs'); function readFruit(fd, fruits){ var buf = new Buffer(5); buf.fill(); //fs.read = function(fd, buffer, offset, length, position, callback) fs.read(fd, buf, 0, 5, null, function(err, bytes, data){ if ( bytes > 0) { console.log("read %dbytes", bytes); fruits += data; readFruit(fd, fruits); } else { fs.close(fd); console.log ("Fruits: %s", fruits); } }); } fs.open('data/fruit.txt', 'r', function(err, fd){ readFruit(fd, ""); }); }

"C:Program Files (x86)JetBrainsWebStorm 11.0.3binrunnerw.exe" F:nodejsnode.exe asyncReadWrite.js Wrote: grapes 7bytes Wrote: banana 7bytes Wrote: orange 7bytes Wrote: apple 6bytes read 5bytes read 5bytes read 5bytes read 5bytes read 5bytes read 2bytes Fruits: grapes banana orange apple Process finished with exit code 0

4.流式读写

/** * Created by Administrator on 2016/3/21. */ var fs = require('fs'); var grains = ['wheat', 'rice', 'oats']; var options = { encoding: 'utf8', flag: 'w' }; //从下面的系统api可以看到 createWriteStream 就是创建了一个writable流 //fs.createWriteStream = function(path, options) { // return new WriteStream(path, options); //}; // //util.inherits(WriteStream, Writable); //fs.WriteStream = WriteStream; //function WriteStream(path, options) var fileWriteStream = fs.createWriteStream("data/grains.txt", options); fileWriteStream.on("close", function(){ console.log("File Closed."); //流式读 streamRead(); }); while (grains.length){ var data = grains.pop() + " "; fileWriteStream.write(data); console.log("Wrote: %s", data); } fileWriteStream.end(); //流式读 function streamRead() { var fs = require('fs'); var options = { encoding: 'utf8', flag: 'r' }; //fs.createReadStream = function(path, options) { // return new ReadStream(path, options); //}; // //util.inherits(ReadStream, Readable); //fs.ReadStream = ReadStream; // //function ReadStream(path, options) //createReadStream 就是创建了一个readable流 var fileReadStream = fs.createReadStream("data/grains.txt", options); fileReadStream.on('data', function(chunk) { console.log('Grains: %s', chunk); console.log('Read %d bytes of data.', chunk.length); }); fileReadStream.on("close", function(){ console.log("File Closed."); }); }

"C:Program Files (x86)JetBrainsWebStorm 11.0.3binrunnerw.exe" F:nodejsnode.exe StreamReadWrite.js Wrote: oats Wrote: rice Wrote: wheat File Closed. Grains: oats rice wheat Read 16 bytes of data. File Closed. Process finished with exit code 0

个人觉得像这些api用一用感受一下就ok了,遇到了会用就行了。