The fs.chmod() method is used to change the permissions of a given path. These permissions can be specified using string constants or octal numbers that correspond to their respective file modes.
Note: The Windows platform only supports the changing of the write permission. It also does not support the distinction between the permissions of user, group, or others.
Syntax:
fs.chmod( 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 of which the permission has to be changed.
- mode: It is string or octal integer constant that denotes the permission to be granted. The logical OR operator can be used to separate multiple permissions.
-
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.chmod() method in Node.js:
Example 1: This example shows the usage of octal integer constants to give the file permissions.
// Node.js program to demonstrate the // fs.chmod() method // Import the filesystem module const fs = require( 'fs' );
// Grant only read permission to user console.log( "Granting only read access to user" );
fs.chmod( "example.txt" , 0o400, () => {
console.log( "\nReading the file contents" );
console.log(fs.readFileSync( "example.txt" , 'utf8' ));
console.log( "\nTrying to write to file" );
try {
fs.writeFileSync( 'example.txt' , "This file has now been edited." );
}
catch (e) {
console.log( "Error Code:" , e.code);
}
// Grant both read and write permission to user
console.log( "\nGranting read and write access to user" );
fs.chmod( "example.txt" , 0o600, () => {
console.log( "Trying to write to file" );
fs.writeFileSync( 'example.txt' , "This file has now been edited." );
console.log( "\nReading the file contents" );
console.log(fs.readFileSync( "example.txt" , 'utf8' ));
});
}); |
Output:
Granting only read access to user Reading the file contents This is an example text file. Trying to write to file Error Code: EACCES Granting read and write access to user Trying to write to file Reading the file contents This file has now been edited.
Example 2: This example shows the usage of string constants and OR operator to give the file permissions.
// Node.js program to demonstrate the // fs.chmod() method // Import the filesystem module const fs = require( 'fs' );
// Grant only read permission to user console.log( "Granting only read access to user" );
fs.chmod( "example.txt" , fs.constants.S_IRUSR, () => {
// Reading the file
console.log( "File Contents:" , fs.readFileSync( "example.txt" , 'utf8' ));
// Trying to write to file
try {
console.log( "\nTrying to write to file" );
fs.writeFileSync( 'example.txt' , "This file now has been edited." );
}
catch (e) {
console.log( "Error Occurred, Error Code:" , e.code);
}
// Granting both read and write permission
console.log( "\nGranting both read and write permission to user" );
fs.chmod( "example.txt" , fs.constants.S_IRUSR | fs.constants.S_IWUSR, () => {
// Check the file mode
console.log( "Current File Mode:" , fs.statSync( "example.txt" ).mode);
console.log( "Trying to write to file" );
fs.writeFileSync( 'example.txt' , "This file now has been edited." );
console.log( "File Contents:" , fs.readFileSync( "example.txt" , 'utf8' ));
});
}); |
Output:
Granting only read access to user File Contents: This file now has been edited. Trying to write to file Error Occurred, Error Code: EACCES Granting both read and write permission to user Trying to write to file File Contents: This file now has been edited.
Reference: https://nodejs.org/api/fs.html#fs_fs_chmod_path_mode_callback