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Node.js | fs.closeSync() Method

  • Last Updated : 29 Apr, 2020

The fs.closeSync() method is used to synchronously close the given file descriptor thereby clearing the file that is associated with it. It allows the file descriptor to be reused for other files. Calling fs.closeSync() on a file descriptor while some other operation is being performed on it may lead to undefined behavior.

Syntax:

fs.closeSync( fd )

Parameters: This method accepts single parameter as mentioned above and described below:

  • fd: It is an integer which denotes the file descriptor of the file of which to be closed.

Below examples illustrate the fs.closeSync() method in Node.js:

Example 1: This example shows the closing of a file descriptor.






// Node.js program to demonstrate the
// fs.closeSync() method
  
// Import the filesystem module
const fs = require('fs');
  
// Get the file descriptor of the given path
file_descriptor = fs.openSync("example.txt");
console.log("The file descriptor is:", file_descriptor);
  
// Close the file descriptor
try {
  fs.closeSync(file_descriptor);
  console.log("\n> File Closed successfully");
} catch (err) {
  console.error('Failed to close file');
}

Output:

The file descriptor is: 3

> File Closed successfully

Example 2: This example shows the closing of a file descriptor and trying to access the closed file descriptor again.




// Node.js program to demonstrate the
// fs.closeSync() method
  
// Import the filesystem module
const fs = require('fs');
  
// Get the file descriptor of the given path
file_descriptor = fs.openSync("example.txt");
console.log("The file descriptor is:", file_descriptor);
  
// Attempting to get stats before closing
console.log("\n> Finding the stats of the file");
try {
  statsObj = fs.fstatSync(file_descriptor);
  console.log("Stats of the file generated");
} catch (err) {
  console.error('Cannot find stats of file', err);
}
  
// Close the file descriptor
try {
  fs.closeSync(file_descriptor);
  console.log("\n> File Closed successfully");
} catch (err) {
  console.error('Failed to close file', err);
}
  
// Attempting to find stats after closing
console.log("\n> Finding the stats of the file again");
try {
  statsObj = fs.fstatSync(file_descriptor);
  console.log("Stats of the file generated");
} catch (err) {
  console.error('Cannot find stats of file', err);
}

Output:

The file descriptor is: 3

> Finding the stats of the file
Stats of the file generated

> File Closed successfully

> Finding the stats of the file again
Cannot find stats of file Error: EBADF: bad file descriptor, fstat
    at Object.fstatSync (fs.js:897:3)
    at Object. (G:\tutorials\nodejs-fs-closeSync\index.js:46:17)
    at Module._compile (internal/modules/cjs/loader.js:956:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)
    at Module.load (internal/modules/cjs/loader.js:812:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)
    at internal/main/run_main_module.js:17:11 {
  fd: 3,
  errno: -4083,
  syscall: 'fstat',
  code: 'EBADF'
}

Reference: https://nodejs.org/api/fs.html#fs_fs_closesync_fd




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