An alternative that I have had kicking around in the back of my mind for a few years is having the process on the read side of the pipe call fcntl() with a new

An alternative that I have had kicking around in the back of my mind for a few years is having the process on the read side of the pipe call fcntl() with a new flag to set an "Accept" set of formats, which the process on the write side of the pipe can retrieve with a 'get' equivalent. If there's a format both sides recognise, they can use that. Both sides just default to plain text so it'll be backwards compatible.