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。