Node.js fs.accessSync() Method

The fs.accessSync() method is used to synchronously test the permissions of a given file or directory. The permissions to be checked can be specified as a parameter using file access constants. It is also possible to check multiple file permissions by using the bitwise OR operator to create a mask with more than one file constant.

Syntax:

fs.accessSync( path, mode )

Parameters: This method accepts two parameters as mentioned above and described below:

• path: It is a String, Buffer or URL which denotes the path of the file or directory for which the permission has to be tested.
• mode: It is an integer value that denotes the permission to be tested for. The logical OR operator can be used to separate multiple permission. It can have the values fs.constants.F_OK, fs.constants.R_OK, fs.constants.W_OK and fs.constants.X_OK. It is an optional parameter. The default value is fs.constants.F_OK.

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

Example 1: This example shows the testing of the read and write permission of a file.

// Node.js program to demonstrate the
// fs.accessSync() method

// Import the filesystem module
const fs = require('fs');

// Allowing only read permission
console.log("Giving only read permission to user");
fs.chmodSync("example.txt", fs.constants.S_IRUSR);

// Test the read permission
console.log('\n> Checking Permission for reading the file');
try {
  fs.accessSync('example.txt', fs.constants.R_OK);
  console.log('File can be read');
} catch (err) {
  console.error('No Read access');
}

// Test both the read and write permission
console.log('\n> Checking Permission for reading and writing to file');
try {
  fs.accessSync('example.txt', fs.constants.R_OK | fs.constants.W_OK);
  console.log('File can be read and written');
} catch (err) {
  console.error('No Read and Write access');
}

Output:

Giving only read permission to user

> Checking Permission for reading the file
File can be read

> Checking Permission for reading and writing to file
No Read and Write access

Example 2: This example shows the testing of a file if it exists.

// Node.js program to demonstrate the
// fs.accessSync() method

// Import the filesystem module
const fs = require('fs');

// Test the if the file exists
console.log('\n> Checking if the file exists');
try {
  fs.accessSync('example.txt', fs.constants.F_OK);
  console.log('File does exist');
} catch (err) {
  console.error('File does not exist');
}

console.log('\nCreating the file');
fs.writeFileSync("example.txt", "Test File");

// Test the if the file exists again
console.log('\n> Checking if the file exists');
try {
  fs.accessSync('example.txt', fs.constants.F_OK);
  console.log('File does exist');
} catch (err) {
  console.error('File does not exist');
}

Output:

> Checking if the file exists
File does not exist

Creating the file

> Checking if the file exists
File does exist

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