Node.js fs.access() Method

The fs.access() method is used to 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.
Note: It is not recommended to use the fs.access() method to check for the accessibility of a file before calling fs.open(), fs.readFile() or fs.writeFile(), because it introduces a race condition since the file state may be changed by other processes after the test.
 

Syntax:  

fs.access( path, mode, callback )

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

• path: It is a String, Buffer or URL that 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.
• callback: It is a function that would be called when the method is executed. 
  
  • err: It is an error that would be thrown if the method fails.

Below examples illustrate the fs.access() method in Node.js:
Example 1: This example shows the testing of the read and write permission of a file. 

Output: 
 

Giving only read permission to the 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.

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_access_path_mode_callback