flush file descriptor in a sh script while passing through a pipe

[Mathieu Prevot]

Hi,

Let's be an example. With 1) I have a progress bar that is updated
regularly but with 2) I have to wait for the end of the download (the
next \n character ?) ...

1)
wget http://tinyurl.com/5ztnb2

2)
wget http://tinyurl.com/5ztnb2 --progress=bar:force 2>&1 | sed
'/^Location/d;/^HTTP/d;/^--/d'

I would like the progress bar to be updated through sed ... how can I
flush the file descriptor from sh or with a tiny command/signal ?

Thanks
Mathieu