Node.js文件操作方法汇总

前端技术 2023/09/04 JavaScript

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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