Need help with serial port

Hi,

I have a external board connected to my serial port. I need to execute "shutdown -r now" command when system boot up. When system boots up it requires a username ans password. Then I need to run my command. I can use rc script but that is rebooting system before it asks for username and password. The command should

  1. first give username to the device
  2. secondly, it should give password
  3. finally it should give "shutdown -r now" command to the board.

This script can run on the host PC and need to log the botting and rebooting messages.

Is it possible to write script on host PC to do it. I am trying to send command as data over serial but its simply echoes on the board but does execute. Please help. __________________