Node.js文件操作二

前面的博客 Node.js文件操作一中主要是对文件的读写操作,其实还有文件这块还有一些其他操作.

一、验证文件path是否正确(系统是如下定义的)

fs.exists = function(path, callback) {
  if (!nullCheck(path, cb)) return;
  var req = new FSReqWrap();
  req.oncomplete = cb;
  binding.stat(pathModule._makeLong(path), req);
  function cb(err, stats) {
    if (callback) callback(err ? false : true);
  }
};

fs.existsSync = function(path) {
  try {
    nullCheck(path);
    binding.stat(pathModule._makeLong(path));
    return true;
  } catch (e) {
    return false;
  }
};

二、获取文件信息

获取文件信息用fs.stats(path,callback)、fs.statsSync(path),它们返回Stats对象.下面是系统定义的Stats对象.

// Static method to set the stats properties on a Stats object.
fs.Stats = function(
    dev,
    mode,
    nlink,
    uid,
    gid,
    rdev,
    blksize,
    ino,
    size,
    blocks,
    atim_msec,
    mtim_msec,
    ctim_msec,
    birthtim_msec) {
  this.dev = dev;
  this.mode = mode;
  this.nlink = nlink;
  this.uid = uid;
  this.gid = gid;
  this.rdev = rdev;
  this.blksize = blksize;
  this.ino = ino;
  this.size = size;
  this.blocks = blocks;
  this.atime = new Date(atim_msec);
  this.mtime = new Date(mtim_msec);
  this.ctime = new Date(ctim_msec);
  this.birthtime = new Date(birthtim_msec);
};

// Create a C++ binding to the function which creates a Stats object.
binding.FSInitialize(fs.Stats);

fs.Stats.prototype._checkModeProperty = function(property) {
  return ((this.mode & constants.S_IFMT) === property);
};

fs.Stats.prototype.isDirectory = function() {
  return this._checkModeProperty(constants.S_IFDIR);
};

fs.Stats.prototype.isFile = function() {
  return this._checkModeProperty(constants.S_IFREG);
};

fs.Stats.prototype.isBlockDevice = function() {
  return this._checkModeProperty(constants.S_IFBLK);
};

fs.Stats.prototype.isCharacterDevice = function() {
  return this._checkModeProperty(constants.S_IFCHR);
};

fs.Stats.prototype.isSymbolicLink = function() {
  return this._checkModeProperty(constants.S_IFLNK);
};

fs.Stats.prototype.isFIFO = function() {
  return this._checkModeProperty(constants.S_IFIFO);
};

fs.Stats.prototype.isSocket = function() {
  return this._checkModeProperty(constants.S_IFSOCK);
};

// Don't allow mode to accidentally be overwritten.
['F_OK', 'R_OK', 'W_OK', 'X_OK'].forEach(function(key) {
  Object.defineProperty(fs, key, {
    enumerable: true, value: constants[key] || 0, writable: false
  });
});

通过Stats对象可以获取该文件的信息例如：文件大小、创建时间、文件类型等。

var fs = require('fs');
fs.stat('file_stats.js', function (err, stats) {
  if (!err){
    console.log('stats: ' + JSON.stringify(stats, null, '  '));
    console.log(stats.isFile() ? "Is a File" : "Is not a File");
    console.log(stats.isDirectory() ? "Is a Folder" : "Is not a Folder");
    console.log(stats.isSocket() ? "Is a Socket" : "Is not a Socket");
    stats.isDirectory();
    stats.isBlockDevice();
    stats.isCharacterDevice();
    //stats.isSymbolicLink(); //only lstat
    stats.isFIFO();
    stats.isSocket();
  }
});

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe file_stats.js
stats: {
  "dev": 1086025760,
  "mode": 33206,
  "nlink": 1,
  "uid": 0,
  "gid": 0,
  "rdev": 0,
  "ino": 12384898975555938,
  "size": 535,
  "atime": "2016-03-12T04:09:24.523Z",
  "mtime": "2014-11-10T22:12:29.000Z",
  "ctime": "2016-03-21T11:39:54.207Z",
  "birthtime": "2016-03-12T04:09:24.523Z"
}
Is a File
Is not a Folder
Is not a Socket

Process finished with exit code 0

三、文件遍历

在其他系统也都有文件遍历.由于文件是树的形式存在,所以使用递归遍历.下面是用异步api,那同步api也能推出来。fs.readdirsync(path).

/**
 * Created by Administrator on 2016/3/22.
 */
var fs = require('fs');
var Path = require('path');
function WalkDirs(dirPath){
    console.log(dirPath);
    fs.readdir(dirPath, function(err, entries){
        for (var idx in entries){
            var fullPath = Path.join(dirPath, entries[idx]);
            (function(fullPath){
                fs.stat(fullPath, function (err, stats){
                    if (stats && stats.isFile()){
                        console.log(fullPath);
                    } else if (stats && stats.isDirectory()){
                        WalkDirs(fullPath);
                    }
                });
            })(fullPath);
        }
    });
}
WalkDirs("../");

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe file_readdir.js
../
..\.idea
..\data
..\asyncReadWrite.js
..\Buffer.js
..\Immediate.js
..\Console.js
..\Interval.js
..\nexttick.txt
..\OpenClose.js
..\StreamReadWrite.js
..\syncReadWrite.js
..\nexttick1.txt
..\.idea\.name
..\.idea\encodings.xml
..\.idea\jsLibraryMappings.xml
..\.idea\misc.xml
..\.idea\modules.xml
..\.idea\NodeJsDemo.iml
..\.idea\workspace.xml
..\nexttick2.txt
..\data\config.txt
..\timer.js
..\SimpleReadWrite.js
..\data\file_readdir.js
..\data\grains.txt
..\data\fruit.txt
..\data\openColse1.txt
..\data\veggie.txt
..\data\openClose.txt

Process finished with exit code 0

四、文件删除

根据前面的几个api,删除有fs.unlink(path,callback)那就有fs.unlink(path).

fs.unlink("../nexttick1.txt", function(err){
    console.log(err ? "File Delete Failed" :  "File Deleted");
});

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe file_readdir.js
File Deleted

Process finished with exit code 0

五、截断文件

截断文件把文件结束设置为比当前小的值来减少文件的大小.

fs.truncate = function(path, len, callback) 

fs.truncateSync = function(path, len) 同步返回布尔值

fs.truncate("test.txt",8,function(err){
    console.log(err?"File Truncate Failed":"File Truncated")
})

六、建立删除文件夹

刚才是遍历用的是readdir,现在是建立则用fs.mkdir(path,[mode],callback)或fs.mkdirSync(path,[mode])。删除则用fs.rmdir(path,callback)或fs.rmdirSync(path).

fs.mkdir("../test",function(err){
    console.log(err?"mkdir Failed":"mkdir success")
    if(!err)
    {
        rmdir();
    }
});
function rmdir()
{
    fs.rmdir("../test",function(err){
        console.log(err?"rmdir Failed":"rmdir success")
    });
}

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe file_readdir.js
mkdir success
rmdir success

Process finished with exit code 0

七.文件重命名

这个重命名不只是改变文件的名字,它可以改变文件的路径。

fs.rename("test","../test1",function(err){
    console.log(err ? "rename Failed" :  "renamed");
})

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe file_readdir.js
renamed

Process finished with exit code 0

八、文件监视

文件发生变化时会执行回调函数.

fs.watchFile("../test1",{persistent:true,interval:5000},function(curr,prev){
    console.log(curr.mtime);
    console.log(prev.mtime);
});
fs.rename("../test1","test",function(err){
    console.log(err ? "rename Failed" :  "renamed");
})

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe file_readdir.js
renamed
Thu Jan 01 1970 08:00:00 GMT+0800 (中国标准时间)
Tue Mar 22 2016 19:30:11 GMT+0800 (中国标准时间)

persistent:持续 interval:时间间隔