#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <linux/serial.h>

void usage(char *name)
{
        fprintf(stderr, "usage: %s <ttyS> [enable|disable]\n", name);

	exit(EXIT_FAILURE);
}

int main(int argc, char *argv[])
{
	int fd, ret;
	struct serial_struct  ss;

	if (argc < 2)
		usage(argv[0]);

        fd = open(argv[1], O_RDWR);
        if (fd < 0) {
                perror("open");
		exit(EXIT_FAILURE);
	}

       	ret = ioctl(fd, TIOCGSERIAL, &ss);
	if (ret < 0 ) {
		perror("ioctl(TIOCGSERIAL)");
		exit(EXIT_FAILURE);
	}

	if (argc < 3) {		/* just read PPS status */
		printf("PPS is %sabled\n",
			ss.flags & ASYNC_HARDPPS_CD ? "en" : "dis");
		exit(EXIT_SUCCESS);
	}

	if (argv[2][0] == 'e' || argv[2][0] == '1')
		ss.flags |= ASYNC_HARDPPS_CD;
	else if (argv[2][0] == 'd' || argv[2][0] == '0')
		ss.flags &= ~ASYNC_HARDPPS_CD;
	else {
		fprintf(stderr, "invalid state argument \"%s\"\n", argv[2]);
		exit(EXIT_FAILURE);
	} 

	ret = ioctl(fd, TIOCSSERIAL, &ss);
	if (ret < 0) {
		perror("ioctl(TIOCSSERIAL)");
		exit(EXIT_FAILURE);
	}

        return 0;
}