#include<unistd.h>
#include<stdlib.h>
#include<stdio.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<errno.h>int main(int argc, char * argv[])
{key_t key;int shm_id;char *ptr;key = ftok("/", 10);shm_id = shmget(key, 100, IPC_CREAT|SHM_R); //创建shmprintf("get the shm id is %d\n", shm_id);  //打印idif((ptr = (char *)shmat(shm_id, NULL, SHM_RDONLY)) == NULL)  //只读方式挂载
    {if(shmctl(shm_id, IPC_RMID, NULL) == -1)  //如果失败则删除perror("Failed to remove memory segment");exit(EXIT_FAILURE);}//打印挂载地址printf("the attach add is %p\n", ptr);printf("now try to write the memory\n");*ptr = 'd';printf("*ptr =%c\n", *ptr);shmdt(ptr);shmctl(shm_id, IPC_RMID, 0);
}

#include<unistd.h>
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<sys/sem.h>
#include<errno.h>int main(int argc, char *argv[])
{int running = 1;int shid;int semid;int value;void *sharem = NULL;struct sembuf sem_b;sem_b.sem_num = 0;sem_b.sem_flg = SEM_UNDO;//创建信号量if((semid = semget((key_t)123456, 1, 0666|IPC_CREAT)) == -1) {perror("semget");exit(EXIT_FAILURE);}//初始化信号量为0if(semctl(semid,0,SETVAL,0) == -1){printf("sem init error");if(semctl(semid, 0, IPC_RMID, 0) != 0){perror("semctl");exit(EXIT_FAILURE);}exit(EXIT_FAILURE);}//创建共享内存shid = shmget((key_t)654321, (size_t)2048, 0600|IPC_CREAT);  //创建共享内存if(shid == -1){perror("shmget");exit(EXIT_FAILURE);}//挂载共享内存到当前进程sharem = shmat(shid, NULL, 0);if(sharem == NULL){perror("shmat");exit(EXIT_FAILURE);}while(running){//测试信号量值，如果为0则可写if((value = semctl(semid, 0, GETVAL)) == 0){printf("write data operate\n");printf("please input something:");scanf("%s", sharem);sem_b.sem_op = 1;//执行信号量加1操作，允许读if(semop(semid, &sem_b, 1) == -1){fprintf(stderr, "semaphore_p failed\n");exit(EXIT_FAILURE);}}//比较是否是结束符号if(strcmp(sharem, "end") == 0)running--;}shmdt(sharem);return 0;
}

#include<unistd.h>
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<sys/sem.h>
#include<errno.h>int main(int argc, char *argv[])
{int running = 1;int shid;int semid;int value;void *sharem = NULL;struct sembuf sem_b;sem_b.sem_num = 0;sem_b.sem_flg = SEM_UNDO;//创建信号量if((semid = semget((key_t)123456, 1, 0666|IPC_CREAT)) == -1) {perror("semget");exit(EXIT_FAILURE);}//创建共享内存shid = shmget((key_t)654321, (size_t)2048, 0600|IPC_CREAT);  //创建共享内存if(shid == -1){perror("shmget");exit(EXIT_FAILURE);}//挂载共享内存到当前进程sharem = shmat(shid, NULL, 0);if(sharem == NULL){perror("shmat");exit(EXIT_FAILURE);}while(running){//测试信号量值，如果为1则可读if((value = semctl(semid, 0, GETVAL)) == 1){printf("read data operate\n");sem_b.sem_op = -1;//执行信号量减1操作，允许写if(semop(semid, &sem_b, 1) == -1){fprintf(stderr, "semaphore_p failed\n");exit(EXIT_FAILURE);}printf("%s\n", sharem);}//比较是否是结束符号if(strcmp(sharem, "end") == 0)running--;}shmdt(sharem);//删除共享内存if(shmctl(shid, IPC_RMID, 0) != 0){perror("shmctl");exit(EXIT_FAILURE);}//删除信号量if(semctl(semid, 0, IPC_RMID, 0) != 0){perror("semctl");exit(EXIT_FAILURE);}return 0;
}