Implementation Under Other Operating Systems
For operating systems other than Unix, no complete mailcap format has yet been specified. If one were to implement a mailcap system on another system, the following things would need to be decided:
A “standard” location for the mailcap file on a system
The semantics for executable commands
Any substitution operators to use
The manner in which a test program returns its results
The manner in which the compose and composetyped commands will return their data
Note that it might not make good sense to define a mailcap file format for all operating systems. If one wanted to create the mailcap functionality under Windows NT, the best place to put it would probably be the Registry, not a flat file.
In conclusion, the mailcap format is a very useful tool to keep from reinventing the wheel on some operating systems. It fits nicely with the Unix philosophy that each tool should be small, specialized, and able to work with countless other via standard mechanisms. Mailcap is one type of glue between these small specialized programs.