What is the best way to do this?

The best way probably depends a lot on what your files look like and what you are going to do to them. Does best mean:

• Fastest
• Most platform-independent
• Least memory usage

If all you want to do is print out lines of files which match the string 'foo', Unix grep would be a good choice:

grep foo dir/*
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If you provide more details, you will surely get good advice from our fellow Monks (maybe even me:)