Possible TODO item: copy to/from pipe

After re-reading what I just wrote to Andreas about how compression of
COPY data would be better done outside the backend than inside, it
struck me that we are missing a feature that's fairly common in Unix
programs.  Perhaps COPY ought to have the ability to pipe its output
to a shell command, or read input from a shell command.  Maybe something
like
COPY mytable TO '| gzip >/home/tgl/mytable.dump.gz';

(I'm not wedded to the above syntax, it's just an off-the-cuff thought.)

Of course psql would need the same capability, since the server-side
copy would still be restricted to superusers.

You can accomplish COPY piping now through psql, but it's a bit awkward:
psql -c "COPY mytable TO stdout" mydb | gzip ...

Thoughts?  Is this worth doing, or is the psql -c approach good enough?
        regards, tom lane