I normally use 'grep' to provide parse out all unwanted extensions and so on by specifying the extension that I do
for example of I have list of files with many different extension types such as .dat, .txt, .pdf, ... and so on, and all I want to know are the .dat files, I use the following command:
cat "list.txt" | grep .dat
however, I know want to do the opposite, that is specify the extension that I do not
want - that is to say that I want all extension types except
what paramater must I specify in grep that will allow me to do this?