rts_test.c

#include <sys/ioctl.h> 

main() {
   int fd;
   fd = open("/dev/ttyUSB0",O_RDWR | O_NOCTTY );//Open Serial Port
   int RTS_flag;
   RTS_flag = TIOCM_RTS;
   ioctl(fd,TIOCMBIS,&RTS_flag);//Set RTS pin
   getchar();
   ioctl(fd,TIOCMBIC,&RTS_flag);//Clear RTS pin
   close(fd);
}