sed: 'F' command missing?

[Neal B.]

Hi,

The sed online documentation (here:
http://www.gnu.org/software/sed/manual/sed.html) describes a 'F'
command that prints out the name of the current input file. I have
version 4.2.1, and this command does not seem to exist. I downloaded
the source code and tried to find evidence of the existence of this
command, but I could not. This command would be useful.

Thanks,
Neal