Node.js fs.filehandle.fd()方法
原文:https://www . geesforgeks . org/node-js-fs-file handle-FD-method/
fs.filehandle.fd() 方法是文件系统模块中类 fs.filehandle 的内置应用编程接口，用于提供该文件句柄对象的数字文件描述符。 语法:
const filehandle.fd()
参数:此方法不接受任何参数。 返回值:这个方法返回这个文件句柄对象的数字文件描述符。 下面的程序说明了 fs.filehandle.fd() 方法在 Node.js: 中的使用示例 1: 文件名:index.js
java 描述语言
// Node.js program to demonstrate the
// filehandle.fd() 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() {
// Initializing filehandle
let filehandle = null;
let value = null;
try {
// Creating and initiating filehandle
filehandle = await
fsPromises.open('example.txt', 'r+');
// Getting the Numeric file descriptor
// by using fd api
value = filehandle.fd;
} finally {
if (filehandle) {
// Close the file if it is opened.
console.log(
"Numeric file descriptor :- " + value);
console.log(
"content of file after operation :- " +
(fs.readFileSync('example.txt')));
await filehandle.close();
}
}
}
funct().catch(console.error);
运行程序前的目录结构:
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 :- ABCD
Numeric file descriptor :- 3
content of file after operation :- ABCD
示例 2: 文件名:index.js
java 描述语言
// Node.js program to demonstrate the
// filehandle.fd() 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() {
// Initializing filehandle
let filehandle = null;
try {
// Creating and initiating filehandle
filehandle = await
fsPromises.open(file, 'r+');
// Getting the Numeric file descriptor
// by using fd api
value = filehandle.fd;
} finally {
if (filehandle) {
// Close the file if it is opened.
console.log(
"Numeric file descriptor :- "
+ value);
console.log("content of file "
+ "after operation :- "
+ (fs.readFileSync(file)));
await filehandle.close();
}
}
}
funct().catch(console.error);
运行程序前的目录结构:
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.
Numeric file descriptor :- 4
content of file after operation :- This is a file containing a collection of books.
参考:T2【https://nodejs . org/dist/latest-v 12 . x/docs/API/fs . html # fs _ file handle _ FDT4】
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