Where do you want to add the new (changed) piece of text? Immediately after the line you modified? At the end of the file? Somewhere else?

A solution like the_pusher_robot's can probably be made to work for you. This might do the trick:

perl -pi.bak -e 's/^cdsadmin\s+-t(.*)/${_}cdsadmin -d$1/' yourfile
[download]

I do recommend providing an argument to -i in order to create a backup of the original otherwise a typo might ruin your whole day. ;-)

-sauoq
"My two cents aren't worth a dime.";