The filename matching interface does not require any changes or extensions to the conventional open() operation in order to obtain variable persistence guarantees. Instead, it determines the volatility specification from the filename. The filename matching interface allows the user to define categories of files based on filenames. Consequently, applications (or existing software libraries) need not be rewritten to use the filename matching interface. To take advantage of MBFS's variable persistence, applications can either be re-linked or can install an open system call hook that intercepts all open operations and redirects them to the filename matching library. This allows legacy applications to benefit from MBFS's variable persistence model without being modified in any way.
The filename matching library maps filenames to full volatility specifications needed by the kernel. Like the category interface, the mapping is stored in environment variables loaded from system or user-defined configuration files. The mapping consists of (regular expression, volatility specification) pairs. At open time, the library matches the filename being opened to a regular expression in the environment. If successful, the library uses the associated volatility specification, otherwise a default persistence is assigned.