进程间通讯之内存共享（实例）

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内存共享概念可以参考前面《进程间通讯之概念》

1、shmget

通过键值创建或获取共享ID

#include <stdio.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/shm.h>#define    MEM_SIZE     4096int main(void){    int   ret,shmid;    key_t key;    //key=ftok();    key=0x666;        //shmid=shmget(IPC_PRIVATE,MEM_SIZE,0600); //create    //如果不存创建  存在报错    //shmid=shmget(key,MEM_SIZE,IPC_CREAT | IPC_EXCL |0600);    //不存创建新 存在获取现有的    shmid=shmget(key,MEM_SIZE,IPC_CREAT|0600);    if(shmid==-1)//error    {       perror("shmget");       return 1;    }    printf("create or get mem id:%d\n",shmid);    struct shmid_ds buf;    ret=shmctl(shmid,IPC_STAT,&buf);    if(ret==-1)   return -1;//error    printf("size:%d nattch:%d\n",buf.shm_segsz,buf.shm_nattch);        getchar();    printf("====del share mem=====\n");    shmctl(shmid,IPC_RMID,NULL);//删除    return 0;}

2、shmat（写入共享数据）

把需要共享的内容写入对应的共享地址

#include <stdio.h>#include <string.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/shm.h>#define    MEM_SIZE     4096//共享内容的字节数int show_shminfo(int shmid);int main(void){    int   ret,shmid;        shmid=shmget(0x666,MEM_SIZE,IPC_CREAT|0600);//0x666为标识键值    if(shmid==-1)//error    {       perror("shmget");       return 1;    }    printf("create or get mem id:%d\n",shmid);    show_shminfo(shmid);    void *addr;    addr=shmat(shmid,NULL,0);//返回共享的地址    if(addr==(void *)-1)    {       perror("shmat");       return 1;    }    printf("addr:%p\n",addr);    show_shminfo(shmid);    strcpy(addr,"Hello Eikis,Just A TEST!");    shmdt(addr);      return 0;}int show_shminfo(int shmid){    struct shmid_ds buf;    int ret;    ret=shmctl(shmid,IPC_STAT,&buf);    if(ret==-1)   return -1;//error    printf("size:%d nattch:%d\n",buf.shm_segsz,buf.shm_nattch); }

3、shmat(读取共享数据)

把共享的数据获取出来

#include <stdio.h>#include <string.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/shm.h>#define    MEM_SIZE     4096int show_shminfo(int shmid);int main(void){    int   ret,shmid;        shmid=shmget(0x666,MEM_SIZE,IPC_CREAT|0600);    if(shmid==-1)//error    {       perror("shmget");       return 1;    }    printf("create or get mem id:%d\n",shmid);    show_shminfo(shmid);    void *addr;    addr=shmat(shmid,NULL,0);    if(addr==(void *)-1)    {       perror("shmat");       return 1;    }    printf("addr:%p\n",addr);    show_shminfo(shmid);    char buf[128];    strcpy(buf,addr);    printf("buf:%s\n",buf);    strcpy(addr,"oooooooooooooooooooooooo");    shmdt(addr);      return 0;}int show_shminfo(int shmid){    struct shmid_ds buf;    int ret;    ret=shmctl(shmid,IPC_STAT,&buf);    if(ret==-1)   return -1;//error    printf("size:%d nattch:%d\n",buf.shm_segsz,buf.shm_nattch); }

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