how to set timer

i need to set a timer to timeout if no data is received from the serial com port.

I cant use sleep() as data may come in anytime and need to be processed immediately. sleep() will halt the program for that time.
How do i set an timer alarm to indicate timeout? Or is there any articles or ways that can help to solve the problem?

Thanks
Marianne

Code:

---

#include <time.h>

int main ( void )
{
  clock_t strt_tmr;
  strt_tmr = clock();
  {  // Begin loop for reading data from serial port

    // Code to scan from serial port goes here.

    if ( clock() > (strt_tmr+10000) ) // check for timeout (10 seconds)
          //set a flag  here to exit loop with timeout error
   
  }// End of code for scanning from serial port

  return 0;
}

---

It's ugly, and it may not work (I can't compile anything where I am). Perhaps if you hold your tongue just right, you'll see what I was trying to aim for.