I have a large folder (~20GB) containing a rather large amount of old archived files (~400K). I only need one though. What would be the easiest way, if possible, to only extract the file I need rather than sitting forever and a day for all of the files to load (if that's even possible)? Right now the folder is sitting on my external hard drive. I also have the original 7zip archive - not sure if that would be easier to extract from.
I'm sure that there are many, many ways that you can do this, but I know that WinRAR allows you to extract individual files from an archive because I use the feature all the time. That would save you having to extract all of the other files extraneously.
EDIT: After re-reading this and realizing that you want this to be done on Mac, you can see this page on unix.stackechange for how to do what you want easily in command line