Subtracting Strings

i had a question. if i needed to subtract two strings( which contain lower case letter words) from one another, how would i approach this or do this? i mean subtract as in:
i have two strings each contains lower case letters and i want to subtract one from the other as in,subtract 'evil' from 'festival' and getting the characters 'fsta' in return.
any help would be appreciated.

Not sure if there is such a function in string.h don't think so but you can make your own, however this is a typical pain in the ass in C string manipulation.

this is the algorithm:

iterate through the second array (the one you are subtracting){
get next letter;
iterate through the first array(the one you are subtracting from){
find first occurance of letter;
make another string from array1 without it;
use pointers and make first array become the new array;
EDIT: break;
}
}

Or you could just print all characters from "festival" that is not the characters e,v,i,l.

What should happen if not all characters are present? Or if a character appear more than once? You might have to make some changes based on the answers of those questions.

Look for a C regex library online. There should be thousands of them.

Yeah, and you might even have one installed. I have a regex.h that is part of BSD standard library.