822headerfilter - filter message header through a program.

822headerfilter prog

822headerfilter reads an 822-format email message from standard input. It executes prog with the header of the message on standard input. If it encounters a permanent error in reading input or executing prog, 822headerfilter exits 100. If it encounters a temporary error in reading input or executing prog, 822headerfilter exits 111. Otherwise, 822headerfilter yields the same exit code as prog.

822headerfilter considers the end of the message or the first line that cannot be part of an 822-format header field to terminate the headers.