You can communicate with Ardunio boards using C language. This is an example of it.
Upload the arduino_client to your board. Then keep it connected to your computer. Update port_name variable in serial_com.c file. Then compile and run it. Now, you can turn on/off the build-in led using your terminal. Also you can send a number to board, then it returns its square. It is restricted with 255 because of int type size.