This program will blink an LED connected to gpio23 of BeagleBoneBlack Board. Inorder for the code to work first set gpio port 23 as output. (echo 23 > /sys/class/gpio/export && echo out > /sys/class/gpio/gpio23/direction))

GPIO_Blink_LED.C

#include<stdio.h>
#include <unistd.h>

int main(int argc, char* argv[])
{
	if(argc!=3){
		printf("Syntax: %s <no_of_times_to_blink> <delay_us>\n",argv[0]);
		return 0;
	}
	int delay=atoi(argv[2]);
	int no=atoi(argv[1]);
	FILE *LEDHandler=NULL;
	char *LEDPath="/sys/class/gpio/gpio23/value";
	int i;
	for(i=0;i<no;i++){
		if(LEDHandler=fopen(LEDPath,"r+")){
			printf("LED on\n\033[F\033[J");
                	fwrite("1", 1, 1,LEDHandler);
                	fclose(LEDHandler);
        	}
        	usleep(delay);
        	if(LEDHandler=fopen(LEDPath,"r+")){
			printf("LED off\n\033[F\033[J");
                	fwrite("0", 1, 1,LEDHandler);
                	fclose(LEDHandler);
        	}
		usleep(delay);
	}

	return 0;
}