Problem in reading input from usb card reader
 

I'm currently doing a project that need to read input from usb magnetic card reader in linux. Do I need to write a usb driver for that purpose? If the usb device is converted into serial port, can I write a serial programming to read input?
Anyway, I used to tried to run a serial program. If I swipe the card then run the program, it works ok - it can read and get the data stored in the card.. but if I run the program then swipe the card, it displays 'segmentation fault' error message... I hope someone could help... thanks..