Node.js fs.filehandle.sync()用法及代码示例

fs.filehandle.sync()方法是文件系统模块中fs.filehandle类的内置应用程序编程接口，用于将该文件的in-core状态与存储设备同步。

用法:

const filehandle.sync()

参数：此方法不接受任何参数作为参数。

返回值：此方法返回未包含的承诺。

下面的程序演示了fs.filehandle.sync()方法的使用。

范例1： 文件名：index.js

// Node.js program to demonstrate the  
// filehandle.sync() method 
const fs = require('fs'); 
const fsPromises = fs.promises; 
  
console.log("content of file before operation:- "
        + (fs.readFileSync('example.txt'))); 
  
// Initiating asyncrionise function 
async function funct() { 
  
    // Initializng following variables 
    let filehandle = null; 
    let prom = null; 
  
    try { 
  
        // Creating and initiating filehandle 
        filehandle = await  
            fsPromises.open('example.txt', 'r+'); 
  
        // Synchronizing the file's in-core state 
        // by using sync() method 
        prom = filehandle.sync(); 
  
    } finally { 
  
        if (filehandle) { 
  
            // Display the result 
            console.log("data is synchronized successfully"); 
            console.log("content of file after operation:- "
                    + (fs.readFileSync('example.txt'))); 
  
            // Close the file if it is opened. 
            await filehandle.close(); 
        } 
    } 
} 
  
funct().catch(console.error);

运行程序之前的目录结构：

运行程序后的目录结构：

使用以下命令运行index.js文件：

node index.js

输出：

content of file before operation:- Content of file:example.txt
data is synchronized successfully
content of file after operation:- Content of file:example.txt

范例2： 文件名：index.js

// Node.js program to demonstrate the  
// filehandle.sync() method 
const fs = require('fs'); 
const fsPromises = fs.promises; 
  
// Data for the new file 
let data = "This is a file containing"
        + " a collection of books."; 
  
// Name of the file to be created 
let file = "books.txt"; 
  
// Creating the new file 'books.txt' 
fs.writeFile(file, data, (err) => { 
  
    // Cathing error 
    if (err) { 
        console.log(err); 
    } 
}); 
  
// Using fs.exists() method  
fs.exists(file, (exists) => { 
    if (exists) { 
        console.log("content of file before"
            + " operation:- " + 
            (fs.readFileSync(file))); 
    } 
}); 
  
// Initiating asyncrionise function 
async function funct() { 
  
    // Initializng filehandle 
    let filehandle = null; 
  
    try { 
  
        // Creating and initiating filehandle 
        filehandle = await  
            fsPromises.open(file, 'r+'); 
  
        // Synchronizing the file's in-core 
        // state by using sync() method 
        prom = filehandle.sync(); 
  
    } finally { 
  
        if (filehandle) { 
  
            // Close the file if it is opened. 
            console.log("data is synchronized"
                    + " successfully"); 
  
            console.log("content of file after"
                + " operation:- " + 
                (fs.readFileSync(file))); 
  
            await filehandle.close(); 
        } 
    } 
} 
  
funct().catch(console.error);

运行程序之前的目录结构：

运行程序后的目录结构：

使用以下命令运行index.js文件：

node index.js

输出：

content of file before operation:- This is a file containing a collection of books.
data is synchronized successfully
content of file after operation:- This is a file containing a collection of books.

参考： https://nodejs.org/dist/latest-v12.x/docs/api/fs.html#fs_filehandle_sync

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注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 Node.js fs.filehandle.sync() Method。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。