shared memory 에 저장된 data 를 읽어오고 싶습니다.

어느 configuration 의 파일에 setting 된 user key와 user size 값으로
공유메모리에 접근하여 그안에 저장된 값을 읽어 오고 싶은데요 이게 가능한가요?

#include
#include
#include
#include
#include
#include
#include
#define MAX_BUF 256
#define MAX 30

int shared(int argc ,char *argv[])
{

FILE *in ;
char s[MAX];
char *ptr;
char *ptr_p;
char *ptr_size;
char *ptr_p2;
struct shmid_ds shmid_buffer;
long size;
int key,shmid, len,rtrn;
char *shared_memory,*sh;
char *sh_array;
char *c1 = "USR_SHMKEY=";
char *c2 = "USR_SHMSIZE=";
char* shared_stuff;
char filename[40]="";
char *string;
int segment_size;
char buf[MAX_BUF];

strcat(filename,argv[2]);
strcat(filename,".conf");

if((chdir("/config"))==-1)
{

fputs("cannnot move to this directory\n",stderr);
exit(1);

}

if((in=fopen(filename,"r")) == NULL)
{

fputs("cannot open input file \n",stderr);
exit(1);
}
while(fgets(s,MAX,in)!=NULL)
{
ptr=strstr(s,c1);
ptr_size=strstr(s,c2);

if(ptr)
{
ptr_p=strtok(ptr,"");
key = atoi(ptr_p+11);
printf("key is : %d\n",key);
}

if(ptr_size)
{

ptr_p2=strtok(ptr_size,"");
size = atol(ptr_p2+12);
printf("SIZE is : %d\n",size);
}
}

//fcloseall();

//if ((shmid = shmget((key_t)key,(size_t)size,IPC_CREAT|0666)) == -1)
if ((shmid = shmget((key_t)key,(size_t)size,S_IRUSR|S_IWUSR)) == -1)
{
perror("shmget failed");
exit(1);
}

shared_memory=(char *)shmat(shmid, NULL,SHM_RDONLY);
if(shared_memory ==(char *)-1){

perror("shmat failed");
exit(1);
}
printf("Memory is atatched at %X\n",(int)shared_memory);

memcpy(buf,shared_memory,sizeof(&shared_memory));
printf("Received from shared memory is %s\n",(char*)shared_memory);
printf("Received from shared memory is %s\n",buf);

shmctl(shmid,IPC_STAT,&shmid_buffer);
segment_size = shmid_buffer.shm_segsz;
printf("segment size : %d\n",segment_size);
shmdt(shared_memory);
return 0;
}

결과 화면

key is : 70500
SIZE is : 67108864
Memory is atatched at B36E5000
Received from shared memory is
Received from shared memory is

일단 그 conf 파일안에 있는 USR_SHMKEY 값과 USR_SHMSIZE 를 읽어드려서 그값들로 공유메모리에 접근하는건데요
잘하고 있는지 몰라서 물어봅니다.
보시다시피 Received from shared memory is 이후 아무 값도 아찍히는데요

제가 잘못 이해하고 있는지 물어보고싶습니다
고수님들 좀 도와주세요ㅣ.