SD card to serial

I have a project idea but am not sure about any code. I need data form an sd card to be sent to the TX/RX lines on the arduino so the data coming from the arduino could be outputted to it. I know this must be a simple code I just don't know how to do it.

Extra info:
The data on the sd is plain text (numbers) stored in a txt file.

There is an example that does exactly that:

File->Examples->SD->DumpFile

I need data form an sd card to be sent to the TX/RX lines on the arduino so the data coming from the arduino could be outputted to it.

Reading data from the SD card is easy. Sending that data to the serial port is easy. "so the data coming from the Arduino could be outputted to it" makes no sense. What data would be coming from the Arduino? The SD card contents, presumably. What is "it" that the data should be output to? Not the SD card, that's clear.

sorry, but I have to say it at least once....

I can understand if you're not American of Indian or British or Australian or one of the other English speaking counties, but DAMN IT! learn how to use spell check and grammar!