Reading GPS data from Serial Port Ubuntu - c

Question

I'm trying to read the GPS data from a serial port, at the moment i can read the data. But im trying to get only the data from "$GPRMC" line only.
I have this code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <sys/ioctl.h>
int main(int argc, char** argv) {
int sfd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY);
if (sfd == -1) {
printf("Error no is : %d\n", errno);
printf("Error description is : %s\n", strerror(errno));
return (-1);
};
struct termios options;
tcgetattr(sfd, &options);
cfsetspeed(&options, B9600);
cfmakeraw(&options);
//options.c_cc[VTIME]=1;
//options.c_cc[VMIN]=100;
//tcflush(sfd, TCIFLUSH);
tcsetattr(sfd, TCSANOW, &options);
usleep(100000);
char serialBuffer[500];
int bytes;
int count;
ioctl(sfd, FIONREAD, &bytes);
int i =0;
char *ret;
char *sepa;
char sepa2[500];
int compare;
for(;;){
if(bytes!=0){
count = read(sfd, serialBuffer, sizeof(serialBuffer));
}
if (count == -1){
printf("ERROR");
break;
}
else if(count == 0){
printf("NODATA");
break;
}
else{
serialBuffer[count] = '\0';
//strcpy(serialBuffer2, serialBuffer);
//printf("%s,", serialBuffer);
sepa = strtok(serialBuffer, "\n");
while(sepa != NULL){
//printf("%s", sepa);
//strcpy(serialBuffer2, sepa);
sepa = strtok(NULL, "\n");
ret = strstr(sepa, "$GPRMC");
if (NULL != ret) {
printf("The substring is: %s\n", ret);
}
}
}
}
close(sfd);
return (EXIT_SUCCESS);
}
This script is always returning me "Segmentation Faul(Core Dumped)", and i dont know why. Im new at c, can any one help me on this?
Thanks