每天撸个API -- File System (4)

摘要：同步写入读取读取文件写入文件附加写入文件监视文件终止监视文件监视检查是否存在创建可读流创建可读流

//Asynchronous fsync
fs.open("/path/demo2", "a", function(err, fd) {
  if (err) throw err;
  fs.fsync(fd, function(err) {
    if (err) throw err;
    fs.close(fd, function(err) {
      if (err) throw err;
      console.log("Complete!")
    });
  });
});

//Synchronous fsync
var fd = fs.openSync("/path/demo2", "a");
fs.fsyncSync(fd);
fs.closeSync(fd);

  
fs.fsync is just an asynchronous node wrapper for unix"s fsync

var buffer = new Buffer("yofine");

//Asynchronous write
fs.open("/path/demo1.txt", "a", function(err, fd) {
  if (err) throw err;
  fs.write(fd, buffer, 0, buffer.length, null, function(err, written, buffer) {
    if (err) throw err;
    console.log( written + "bytes were written from buffer");
    fs.close(fd, function(err) {
      if (err) throw err;
      console.log("Complete");
    });
  });
});

//Synchronous write
var fd = fs.openSync("/path/demo1.txt", "a");
var written = fs.writeSync(fd, buffer, 0, buffer.length, null);
console.log(written + "bytes were written from buffer");
fs.closeSync(fd);

var buffer = new Buffer(100);

//Asynchronous read
fs.open("/path/demo1.txt", "r", function(err, fd) {
  if (err) throw err;
  fs.read(fd, buffer, 0, buffer.length, null, function(err, bytesRead, buffer) {
    if (err) throw err;
    console.log("bytesRead : " + bytesRead);
    fs.close(fd, function(err) {
      console.log("Complete!");
    });
  });
});

//Synchronous read
var fd = fs.openSync("/path/demo1.txt", "r");
var bytesRead =  fs.readSync(fd, buffer, 0, buffer.length, null);
console.log("bytesRead : " + bytesRead);
fs.close(fd);

//Asynchronous readFile
fs.readFile("/path/demo1.txt", function(err, data) {
  if (err) throw err;
  console.log(data);
});

//Synchronous readFile
var data = fs.readFileSync("/path/demo1.txt");
console.log(data);

  
replacing the file if it already exists. data can be a string or a buffer.

//Asynchronous writeFile
fs.writeFile("/path/demo1.txt", "hello yofine", function(err) {
  if (err) throw err;
  console.log("saved");
});

//Synchronous writeFile
fs.writeFileSync("/path/demo1.txt", "hello yofine");

  
Asynchronously append data to a file, creating the file if it not yet exists. data can be a string or a buffer.

//Asynchronous appendFile
fs.appendFile("/path/demo1.txt", "yofine", function(err) {
  if (err) throw err;
  console.log("Complete");
});

//Synchronous appendFile
fs.appendFileSync("/path/demo1.txt", "yofine");
console.log("Complete");

fs.watchFile("/path/demo1.txt", function(curr, prev) {
  console.log("the current mtime is: " + curr.mtime);
  console.log("the previous mtime was: " + prev.mtime);
})

fs.unwatchFile("/path/demo1.txt")

  
Watch for changes on filename, where filename is either a file or a directory. The returned object is a fs.FSWatcher.

fs.watch("/path/demo1.txt", function(event, filename) {
  console.log(event);
  console.log(filename);
});

//Asynchronous exists
fs.exists("/path/demo1.txt", function(exists) {
  console.log(exists ? "exists" : "not exists");
})

//Synchronous exists
var exists = fs.existsSync("/path/demo1.txt");
console.log(exists ? "exists" : "not exists");

  
options is an object with the following defaults:

{ flags: "r",
  encoding: null,
  fd: null,
  mode: 0666,
  autoClose: true
}

fs.createReadStream("/path/demo1.txt", options);

var http = require("http");
var fs = requ{ flags: "r",
  encoding: null,
  fd: null,
  mode: 0666,
  autoClose: true
}ire("fs");

http.createServer(function(req, res) {

  var filename = __dirname+req.url;

  var readStream = fs.createReadStream(filename);

  readStream.on("open", function () {
    readStream.pipe(res);
  });

  readStream.on("error", function(err) {
    res.end(err);
  });
}).listen(8080);

  
options is an object with the following defaults:

{ flags: "w",
  encoding: null,
  mode: 0666 }

fs.createWriteStream("/path/demo1.txt", options)

var http = require("http");
var fs = require("fs");

http.createServer(function(req, res) {
  var writeStream = fs.createWriteStream("./output");

  req.pipe(writeStream);

  req.on("end", function () {
    res.writeHead(200, {"content-type":"text/html"});
    res.end("



");
  });

  writeStream.on("error", function (err) {
    console.log(err);
  });
}).listen(8080);