var absolute_path = path.join(__dirname, 'a', 'b.txt');

var path = require('path');
var basename = path.basename(absolute_path);
console.log(basename);

var path = require('path');
var dirname = path.dirname(absolute_path);
console.log(dirname);

var path = require('path');
var extname = path.extname(absolute_path);
console.log(extname)

var path = require('path');
var format = path.format({		// 存在dir属性会忽略root，存在base属性会忽略name和ext
    root: '',
  	dir: path.dirname(absolute_path),
    base: path.basename(absolute_path),
  	name: '',
  	ext: ''
});

var path = require('path');
var parse = path.parse(absolute_path);      //解析路径为五个基本属性： root,dir,base,ext,name
console.log(parse);

var path = require('path');
var resolve = path.resolve('w', 'ab', '../c');
console.log(resolve);       // 返回：/Users/xxl340395462/nodejs/demo-buffer/w/c

var path = require('path');
var sep = path.sep;
console.log(sep);

var path = require('path');
var delimiter = path.delimiter;     // 路径定界符
console.log(delimiter);

var fs = require('fs');
fs.writeFile('a.txt', '', {			//写入数据类型: string,buffer,url,fd(即文件描述符)
  encoding: 'utf8',
  mode: '0o666',			// 权限，可通过chmod更改
  flag: 'w'    //a追加,w写入,r读取，a+读取和追加,w+读取和写入,r+读取和写入,'a'、'a+'、'w'、'w+'下如果文件不存在则创建文件
}, (err) => {
  if (err) throw err;
  console.log('文件创建/写入成功');
});

var fs = require('fs');
fs.readFile('a.txt', (err, data) => {
  if (err) throw err;
  console.log('读取文件内容: ', data);
});

var fs = require('fs');
fs.open('a.txt', 'a+', (err, fd) => {
  if (err) throw err;
  var write_data = '写入数据';
  // 或者write_data可以是buffer
  fs.write(fd, '写入数据', write_data, 0, 'utf8', (err, written, data) => {
    if (err) throw err;
    console.log('写入数据的字节数: ', written);
    console.log('写入的数据: ', data);     // 如果传入的是buffer，则返回的是buffer
    
    fs.read(fd, Buffer.alloc(8), 0, 8, null, (err, bytesRead, buffer) => {
      if (err) throw err;
      console.log('读取字节数: ', bytesRead);
      console.log('写入buffer', buffer.toString());
      
      fs.close(fd, (err) => {
        if (err) throw err;
        console.log('关闭成功');
      });
    })
  })
})

var fs = require('fs');
fs.unlink('a.txt', (err) => {
  if (err) throw err;
  console.log('文件已删除');
});

var fs = require('fs');
fs.copyFile('a.txt', 'dest/a.txt', (err) => {
  if (err) throw err;
  console.log('源文件已拷贝到目标文件');
});

var fs = require('fs');
fs.mkdir('dest/a',{ recursive: true }, (err) => {
  if (err) throw err;
  console.log('文件夹创建成功');
});

var fs = require('fs');
fs.rmdir('dest/a', (err) => {
  if (err) throw err;
  console.log('文件夹删除成功');
});

var fs = require('fs');
fs.rename('dest/a', 'dest/b' (err) => {
  if (err) throw err;
  console.log('文件夹重命名成功');
});

var fs = require('fs');
fs.readdir('dest/a', (err, files) => {   //files是数组，元素为文件/文件夹名
  if (err) throw err;
  console.log('文件夹下资源: ', files);
});

var fs = require('fs');
fs.stat('dest/a.txt', (err, stats) => {   //stats是类fs.Stat的实例
  if (err) throw err;
  console.log('文件状态: ', stats);
});