For starters, you can have a look at Basic Input and Output and File Input and Output or Re: How do I read the contents of a file?.

For regular expressions String matching and Regular Expressions and the items linked to it, are surely a must.

Of course, you have already read Common Beginner Mistakes and will heed its warnings.

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law