node.js 读写文件

            
                //path包含处理路径的方法
var path = require(‘path‘);
//fs模块包含所有文件操作函数
var fs = require(‘fs‘);

var str1 = "/home";
var str2 = "/git";
var str3 = "/NodeExploring";
//路径拼接
var dirPath = path.join(str1, str2, str3);
console.log(dirPath);

var str4 = "./IO";
//path.resolve将多个路径解析未一个规范的绝对路径
var dirPath2 = path.resolve(dirPath, str4);
console.log(dirPath2)

var str5 = "aaa";
var str6 = "./bbb";
//如过解析的路径不是绝对路径则将，将将当前路径加到前面构成绝对路径
var dirPath3 = path.resolve(str5, str6);
console.log(dirPath3);

var str7 = "/home/renlan/tem";
//计算一个路径到另一个路径的相对路径
var dirPath4 = path.relative(dirPath, str7);
console.log(dirPath4);

var str8 = "/home/renlan/tem.txt";
//获取文件所在目录
var dirPath5 = path.dirname(str8);
console.log(dirPath5);

//获取文件的扩展名
var extName = path.extname(str8);
console.log(extName);

//获取文件名,第二个参数未文件的扩展名
var fileName = path.basename(str8, extName);
console.log(fileName);

//获取系统路径的分隔符unix:‘/‘, windows:‘\\‘var sep = path.sep;
console.log(sep);

/************
 * 获取或目录信息
 * fs.stat() 返回一个stats对象
 * 
 * atime "Access Time"
 * mtime "Modified Time"
 * ctime "Change Time"
 * birthtime "Birth Time" 
 * *************/
fs.stat(‘./test‘, function (err, stats) {
    if (err) throw err;
    //console.log(stats);
});

//读取整个文件
fs.readFile(‘./test‘, ‘UTF-8‘, function (err, data) {
    if (err) throw err;
    console.log( "read whole file: "+data);
});

/***************
 * fs.write(fd, buffer, offset, length[, position], callback)
 * fd 文件指针
 * buffer 写入数据的缓存
 * offset 缓存写入时开始的地方
 * position 写入文件开始的地方，null表示从当前位置读取
 * callback 三个参数 (err, written, buffer)
 * written 写入的字节数
 * ***********************/
fs.open(‘./test‘, ‘a‘, (err, fd) => {
    var buffer = new Buffer("Writing to this file"),
        offset = 0,
        length = buffer.length,
        position = null;

    fs.write(fd,
        buffer,
        offset,
        length,
        position,
        (err, writen) => {
            if (err) throw err;
            console.log(‘write file successfully‘);
            console.log("write " + writen + " bytes");
            fs.close(fd,(err)=>{
                if(err) throw err;
            });
        });
});


/***************
 * fs.read(fd, buffer, offset, length, position, callback)
 * buffer 写入数据的缓存
 * offset 缓存写入时开始的地方
 * length 读取的字节数
 * position 读取文件开始的地方，null表示从当前位置读取
 * callback 三个参数 (err, bytesRead, buffer)
 * ********************/
fs.open(‘./test‘, ‘r‘, (err, fd) => {
    if (err) throw err;
    var readBuffer = new Buffer(1024),
        bufferOffset = 0,
        bufferLength = readBuffer.length,
        filePosition = 0;
    fs.read(fd,
        readBuffer,
        bufferOffset,
        bufferLength,
        filePosition,
        (err, readBytes, buffer) => {
            if (err) throw err;
            console.log(‘read ‘ + readBytes + ‘ bytes‘);
            if (readBytes > 0) {
                //切分缓冲区，取出读入的数据部分
                console.log(buffer.slice(0, readBytes));
                console.log("read file from buffer: "+buffer.slice(0, readBytes).toString());
            }
            //关闭文件
            fs.close(fd,(err)=>{
                if(err) throw err;
            });

        });                                                                                                                                         
});