Redirection (<>)

[Jan Kroken <jankr@xxxxxxxxxx>]

>From zsh.info:

`<>WORD'
     Open file WORD for reading and writing as standard input.  If the
     file does not exist then it is created.

and here's what happens when I try to use it.

~/tmp% cat > f         
a b d f
c d c
c c d
e c d
~/tmp% sed "s/c/f/g" <> f
a b d f
f d f
f f d
e f d
~/tmp% cat f
a b d f
c d c
c c d
e c d
~/tmp% 

And my question is; Why does the output from sed go to stdout?

What does <> really mean?

-- 
                                                     -jk