Bash: is there a way to search for a particular string in a directory of files?

Problem

Possible Duplicate: Search for a text pattern in linux In bash, I was wondering if there were any commands that would let you know if a particular string you are looking for exists within the files located in the current directory you are in. Say you are looking for the function 'toUpperCase()' within a set of C files in your current directory. There are a lot of files, so you wouldn't want to manually open each one up using vim and check for the string 'toUpperCase' because that would take a lot of time. If not a bash command line, is there another method to do this efficiently?