Grant access to sub-directories by IP addresses

We need to grant access to all sub-directories by using a number of IP addresses once only. We already do this by having the IP addresses in multiple .htaccess files, but this is time-consuming to create and becomes difficult to maintain. Current: jnirs |-v1 .htaccess with multiple IP addresses |-v2 .htaccess with multiple IP addresses |... |-v21 .htaccess with multiple IP addresses Possible solution: jnirs .htaccess with multiple IP addresses |-v1 .htaccess using IP addresses from level above |-v2 .htaccess using IP addresses from level above |... |-v21 .htaccess using IP addresses from level above Other possible solutions are welcomed, but cannot include access to server-level files such as httpd.conf. PREVIOUS JOB DESCRIPTION LEFT FOR BACKGROUND INFORMATION ONLY We publish subscription periodicals and use .htaccess files to allow only subscribers access to the PDFs of individual articles. Access can be granted by IP address(es) or username/password. There are three periodicals stretching back up to 24 years; some subscribers may only have access to one periodical/year, others to many. The generation of the individual .htaccess files is automated and the whole system works for us as far as it goes. However, it is essential for us that our content is indexed by Google Scholar, and they require that we redirect requests to the full-text PDF that they index to an abstract page which can be read by anyone, regardless of whether they are subscribers. The abstract pages already exist. I have mod_rewrite code for use within an .htaccess that performs the redirection, however, this interferes with the .htaccess files in individual sub-directories that controls access to the PDFs within those directories. I need someone to make the necessary changes to grant/deny access to particular sub-directories when that request is made from our server but redirect it when it comes from a Google server. The difficulty lies in overcoming the interference between two .htaccess files or in constructing a similar but alternative access control system that overcomes the problem. I can provide examples of the .htaccess files, including the mod_rewrite code, the directory structure and further information on request. The server is a Managed Virtual Server and access to server-level files such as [login to view URL] is not possible. The hosting company would make a one-off change to such files, but we need to be able to update IP addresses, usernames etc. for existing as well as new subscribers, and such continual change would not be an option. The server is a Linux-based server running Apache, PHP and MySQL (version numbers available on request if needed). The website is based on Drupal 7, BUT the database that runs this periodical system is separate from Drupal and uses custom PHP code, albeit running within a Drupal node. I do not think that Drupal experience is necessary or relevant for this job, but I mention it for completeness.