#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#define FTOK_PATH            "/dev/zero"
#define FTOK_PROJID          0x22

typedef struct st_student
{
    char            name[64];
    int             age;
} t_student;

int main(int argc, char **argv)
{
    key_t          key;
    int            shmid;
    int            i;
    t_student     *student;

    if( (key=ftok(FTOK_PATH, FTOK_PROJID)) < 0 ) 
    {   
	printf("ftok() get IPC token failure: %s\n", strerror(errno)); 
	return -1;
    }

    shmid = shmget(key, sizeof(t_student), IPC_CREAT|0666);
    if( shmid < 0)
    {
	printf("shmget() create shared memroy failure: %s\n", strerror(errno));
	return -2;
    }

    student = shmat(shmid, NULL, 0);
    if( (void *)-1  == student )
    {
	printf("shmat() alloc shared memroy failure: %s\n", strerror(errno));
	return -2;
    }

    strncpy(student->name, "zhangsan", sizeof(student->name));
    student->age = 18;

    for(i=0; i<4; i++)
    {
	student->age ++;
        printf("Student '%s' age [%d]\n", student->name, student->age);
	sleep(1);
    }

    shmdt(student);

    shmctl(shmid, IPC_RMID, NULL);

    return 0;
}