/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun IoT System Studio
 *                  All rights reserved.
 *
 *       Filename:  shm_read.c
 *    Description:  This file is Shared Memory(read) example program
 *
 *        Version:  1.0.0(11/10/2025)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "11/10/2025 11:08:24 AM"
 *
 ********************************************************************************/
#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 student_s
{
    char            name[64];
    int             age;
} student_t;

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

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

    shmid = shmget(key, sizeof(*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;
    }

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

    shmdt(student);
    shmctl(shmid, IPC_RMID, NULL);

    return 0;
}