How to shutdown after finished download?

In linux managers has not this function. But I need it...
I tried

wget [url]; shutdown -h now

but with lack of chance. It want root password. Some people from IRC offered me to remove the password. I think that this is not a good decision. I wrote some posts in the forums but still not answers.

Actually at the end I found a very simple decision - there is a working app which can turn off the power of PC. And the program is - wxDownload Fast