/*********************************************************************************
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* Copyright: (C) 2025 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: shm_read.c
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* Description: This file is Shared Memory(read) example program
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*
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* Version: 1.0.0(11/10/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "11/10/2025 11:08:24 AM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/ipc.h>
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#include <sys/shm.h>
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#define FTOK_PATH "/dev/zero"
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#define FTOK_PROJID 0x22
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typedef struct student_s
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{
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char name[64];
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int age;
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} student_t;
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int main(int argc, char **argv)
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{
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student_t *student;
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key_t key;
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int shmid;
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int i;
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if( (key=ftok(FTOK_PATH, FTOK_PROJID)) < 0 )
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{
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printf("ftok() get IPC token failure: %s\n", strerror(errno));
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return -1;
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}
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shmid = shmget(key, sizeof(*student), IPC_CREAT|0666);
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if( shmid < 0)
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{
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printf("shmget() create shared memroy failure: %s\n", strerror(errno));
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return -2;
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}
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student = shmat(shmid, NULL, 0);
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if( (void *)-1 == student )
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{
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printf("shmat() alloc shared memroy failure: %s\n", strerror(errno));
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return -2;
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}
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for(i=0; i<4; i++)
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{
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printf("Student '%s' age [%d]\n", student->name, student->age);
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sleep(1);
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}
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shmdt(student);
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shmctl(shmid, IPC_RMID, NULL);
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return 0;
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}
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