section4.5.md

Section 4.5: Check Permissions of a File or Directory

fs.access() determines whether a path exists and what permissions a user has to the file or directory at that path. fs.access doesn't return a result rather, if it doesn't return an error, the path exists and the user has the desired permissions. The permission modes are available as a property on the fs object, fs.constants

• fs.constants.F_OK - Has read/write/execute permissions (If no mode is provided, this is the default)
• fs.constants.R_OK - Has read permissions
• fs.constants.W_OK- Has write permissions
• fs.constants.X_OK- Has execute permissions (Works the same as fs.constants.F_OK on Windows)

Asynchronously

const fs = require('fs');

let path = '/path/to/check';

// checks execute permission
fs.access(path, fs.constants.X_OK, (err) => {
  if (err) {
    console.log("%s doesn't exist", path);
  } else {
    console.log('can execute %s', path);
  }
});

// Check if we have read/write permissions
// When specifying multiple permission modes
// each mode is separated by a pipe : `|`
fs.access(path, fs.constants.R_OK | fs.constants.W_OK, (err) => {
  if (err) {
    console.log("%s doesn't exist", path);
  } else {
    console.log('can read/write %s', path);
  }
});

Synchronously

fs.access also has a synchronous version fs.accessSync. When using fs.accessSync you must enclose it within a try/catchblock.

// Check write permission
try {
  fs.accessSync(path, fs.constants.W_OK);
  console.log('can write %s', path);
}
catch (err) {
  console.log("%s doesn't exist", path);
}