Script to open and search certain files for key words

I need a script/program that will allow me to search various files for key words. Each key word must be searched separately so I know which words were found in each file. These will later be scored by which words were found so some type of flat file recording the words and filename will be required to be output. (i.e. filename, keyword1, keyword2, keyword3....) This script needs to be able to search the following document types: PDF MS Word (95-2010) MS Excel (95-2010) Text files RTF files I will need to be able to pass the program a parameter of a directory that contain the files. You can skip any files that are not of the listed types. ## Deliverables Speed is king in this program. We will be searching several hundred thousand files on a fairly regular basis.