A única coisa em que consigo pensar é retirada diretamente da página de manual, seção PROGRESS METER
:
If you prefer a progress "bar" instead of the regular meter, -# is your friend.
Exemplo:
delicious:~ ajanssen$ curl -# http://www.heise.de > bla
######################################################################## 100,0%
Vs:
delicious:~ ajanssen$ curl http://www.heise.de > bla
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 98k 0 98k 0 0 164k 0 --:--:-- --:--:-- --:--:-- 169k