replcement/translate of ' to ''

Hi
i have a variable whose value contains '(single quote)
i want to replace single quote with two single quotes

ex-
i want to replace
abc's second center

with abc''s second center.

Plz help me.

thanks

show us what you've got

You should have tried , before posting.

something like this :

TES>va="abc'"

TES>echo $va | sed "s/'/''/g"
abc''