You need to open the serial, then use stty to set the rs-232 parameters to match your printer. The device of your serial port will vary depending on the hardware you use. I believe the typical ports on a PC are /dev/ttyS0, /dev/ttyS1
A brute force example would be something like:
Code:
cat </dev/ttyS0 &
stty 9600 cs8 -ixon -ixoff -opost </dev/ttyS0
cat file >/dev/ttyS0
Personally, I would prefer to use CUPS and let hit deal with the serial port.