segment fault when I use shmat - c

Question

When I reach the line routerInfo->areaID, I got segment fault: 11 on that part.
It seem that I do not allocate the memory successfully.
I just do not know why.
Can any one solve this problem?
My header is like this:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include<memory.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/ipc.h>
#include <semaphore.h>
#include <time.h>
#include <signal.h>
#include <fcntl.h>
#include <stdbool.h>
#include <netdb.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#define QUEUE_SIZE 300
#define MAX_CONN 10
#define TYPE_ROUTE 1
#define TYPE_TERMINAL 2
#define CONN_INIT false
#define CONN_ESTB true
#define CSPORT 39246
struct localInfo{
char router_ID[16];
int helloTime;
int protocol_Version;
int update_Interval;
int area_ID;
int neighborNum;
};
//shared information struct
and My main function is:
#include "BasicHeader.h"
int shared_hello, shared_lsa, shared_ping, shared_data, shared_localInfo;//using shared memory
pid_t childpid;//using for child process
int main(){
printf("Starting router ... ");
sleep(1);
key_t keyForLocalInfo = ftok(".", 1);
shared_localInfo = shmget ( keyForLocalInfo , sizeof(struct localInfo) , IPC_CREAT) ;
if (shared_localInfo == -1) {perror("error creating");exit(1);}
printf("shared_localInfo: %d\n", shared_localInfo);
//creating the queue for shared_localInfo
system("ipcs -m");
//show the shm status
//creating the sharing memory finished
struct localInfo *routerInfo = (struct localInfo*) shmat (shared_localInfo, (void *)0, 0);
if (routerInfo == NULL) {
perror("shmat");exit(1);
}
routerInfo->area_ID = 0;
routerInfo->helloTime = 45;
routerInfo->neighborNum = 0;
routerInfo->protocol_Version = 1;
routerInfo->update_Interval = 180;
shmdt(routerInfo);
int err = 0;
if ((err = shmctl(shared_localInfo, IPC_RMID, 0) == -1))
perror("shmctl shared_localInfo");
}

Answer 1

Change the permissions on semget to allow access e.g.
shmget(keyForLocalInfo, sizeof(struct localInfo),
IPC_CREAT | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
Note that shmat returns a ptr set to -1, not NULL, and thus the error check was not catching the error. The code should have been
struct localInfo *routerInfo = (struct localInfo*) shmat (shared_localInfo, (void *)0, 0);
if (routerInfo == (void *) -1)
{
perror("shmat");
exit(1);
}