Reading/Writing in Serial Port

In my previous post, i have mentioned something about playing with serial ports and today i will continue to give small description about the problems i encountered. Hopefully somebody have the answer and can give the answer for me.

I had a data which should be captured by tapping into the serial ports and then it had to be sent again to output device which should be a serial ports again. I can capture the data from the serial ports easily, but it's not a human readable (well, it's ASCII, but it has lots of other data, probably used for control characters). I need to decode the format of the data and then i have to write some code to send modified output to the output device again. So far, i found Michael R. Sweet's Serial Programming Guide for POSIX Operating Systems. I think it's one of the best tutorial on the Internet about serial programming as many people tends to refer serial programming problems to this site and i'm looking on it right now. Hopefully i can understand this, as serial programming is a new thing for me :)