Scheduling shutdown after download completion.
 

Is there any way to schedule shutdown, from terminal,right after some currently running download in mozilla completes??

Not that I'm aware of. However, you COULD always use wget for the download in a script, and have a shutdown after it. Like
If you run that as root, you're all set.

Thanks,i ll try that next time.This time,I scheduled it a couple of minutes ahead the expected time to complete the download.

That's one way to do it, another is to use ';' or '&&' to run both commands, one after the other. Like this:
(first become root!)
or:
Difference is that when using ';', if the first command (wget) fails, the computer will still shutdown. This won't happen with '&&'

no need for a script!

If you have a rough idea of when the download will complete, you can use the sleep command:

sleep 60m ; shutdown -h now

or sleep 2h ; shutdown -h now

It won't be as exact as the method above, but it's an option. :)

Also you can schedule shutdown times with the shutdown command itself. See man shutdown.

Wouldn't it be the simplest solution to use a download-manager that allows it, like JDownloader?
Estimation of the remaining download-time can be a major failure, because in most cases you don't the load of the server at any time.

maybe, may be not... usually doing things in the terminal is the cleanest way to accomplish something. Plus, its just a one-line command