A substitution of the form $]url[ is specially handled. url can be any supported URL type including file: and data:.Standard LDAP URLs can also be used, with the host and port omitted; the host and part are instead specified with the LDAP_HOST and LDAP_PORT options. That is, the LDAP URL should be specified as:
where the square bracket characters [ and ] shown above indicate optional portions of the URL. The dn is required and is a distinguished name specifying the search base. The optional attributes, scope, and filter portions of the URL further refine the information to return. That is, attributes specifies the attribute or attributes to be returned from LDAP directory entries matching this LDAP query. The scope may be any of base (the default), one, or sub. filter describes the characteristics of matching entries.
Certain LDAP URL substitution sequences are available for use within the LDAP query URL. The length of URLs can be 1024 characters. This also applies to expressions created by mappings and mapping calls to other mappings.