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Node.js文件操作一

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)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.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)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.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)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.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)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.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。


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