This Google Script prints the sharing access and permissions of all files in your Google Drive. This helps you determine who has access to your Google Drive files. It uses the DriveApp service to retrieve all the files in your Google Drive and emails the report to the email address of the authorized Google user.

/*

  ======================================
  Who Can See Your Files in Google Drive
  ======================================

  Written by Amit Agarwal on 01/11/2014
  Tutorial :: http://labnol.org/?p=28237

*/

function ScanGoogleDrive() {
  var files = DriveApp.getFiles();
  var timezone = Session.getScriptTimeZone();
  var email = Session.getActiveUser().getEmail();

  var file, date, access, url, permission;
  var privacy, view, viewers, edit, editors;

  var rows = [['File Name', 'Who has access?', 'Date Created']];

  while (files.hasNext()) {
    file = files.next();

    try {
      access = file.getSharingAccess();
      permission = file.getSharingPermission();
      viewers = file.getViewers();
      editors = file.getEditors();

      view = [];
      edit = [];

      date = Utilities.formatDate(file.getDateCreated(), timezone, 'yyyy-MM-dd HH:mm');
      url = '<a href="' + file.getUrl() + '">' + file.getName() + '</a>';

      for (var v = 0; v < viewers.length; v++) {
        view.push(viewers[v].getName() + ' ' + viewers[v].getEmail());
      }

      for (var ed = 0; ed < editors.length; ed++) {
        edit.push(editors[ed].getName() + ' ' + editors[ed].getEmail());
      }

      switch (access) {
        case DriveApp.Access.PRIVATE:
          privacy = 'Private';
          break;
        case DriveApp.Access.ANYONE:
          privacy = 'Anyone';
          break;
        case DriveApp.Access.ANYONE_WITH_LINK:
          privacy = 'Anyone with a link';
          break;
        case DriveApp.Access.DOMAIN:
          privacy = 'Anyone inside domain';
          break;
        case DriveApp.Access.DOMAIN_WITH_LINK:
          privacy = 'Anyone inside domain who has the link';
          break;
        default:
          privacy = 'Unknown';
      }

      switch (permission) {
        case DriveApp.Permission.COMMENT:
          permission = 'can comment';
          break;
        case DriveApp.Permission.VIEW:
          permission = 'can view';
          break;
        case DriveApp.Permission.EDIT:
          permission = 'can edit';
          break;
        default:
          permission = '';
      }

      view = view.join(', ');

      edit = edit.join(', ');

      privacy +=
        (permission === '' ? '' : ' ' + permission) +
        (edit === '' ? '' : ', ' + edit + ' can edit') +
        (view === '' ? '' : ', ' + view + ' can view');

      rows.push([url, privacy, date]);
    } catch (e) {
      Logger.log(e.toString());
      Logger.log(file.getName());
    }
  }

  var html = '<p>File Permissions Report for Google Drive</p>';

  html += '<table><tr><td><b>' + rows[0].join('</b></td><td><b>') + '</b></td></tr>';

  for (var i = 1; i < rows.length; i++) {
    html += '<tr><td>' + rows[i].join('</td><td>') + '</td></tr>';
  }

  html +=
    "</table><br>For help, refer to this <a href='http://www.labnol.org/internet/google-drive-access/28237/'>online tutorial</a> written by <a href='https://ctrlq.org/'>Amit Agarwal</a>.";

  MailApp.sendEmail(email, 'Google Drive - File Permissions Report', '', { htmlBody: html });
}