Node.js fs.filehandle.fd() Method

The fs.filehandle.fd() method is an inbuilt application programming interface of class fs.filehandle within File System module which is used to provide the numeric file descriptor of this file handle object.
Syntax: 
 

const filehandle.fd()

Parameter: This method does not accept any parameter.
Return value: This method returns the numeric file descriptor of this file handle object.
Below programs illustrates the use of fs.filehandle.fd() method in Node.js:
Example 1: Filename: index.js 
 

Directory structure before running the program: 
 

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Directory structure after running the program: 
 

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Run index.js file using the following command: 
 

node index.js

Output: 
 

content of file before operation :- ABCD
Numeric file descriptor :- 3
content of file after operation :- ABCD

Example 2: 
Filename: index.js 
 

Directory structure before running the program: 
 

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Directory structure after running the program: 
 

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Run index.js file using the following command: 
 

node index.js

Output: 
 

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.

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