共享内存

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两个进程共享一块内存

server

#include<unistd.h>#include<stdlib.h>#include<stdio.h>#include<string.h>#include<sys/shm.h>#include "shm_com.h"int main(){    int running = 1;    void *shared_memory = (void *)0;    struct share_use_st *shared_stuff;    int shmid;    srand((unsigned int)getpid());    //创建一个可读可写的共享内存    shmid = shmget((key_t)1234,sizeof(struct share_use_st),0666|IPC_CREAT);                                                                                                                                                                                                       if(shmid == -1){        fprintf(stderr,"shmget faild\n");        exit(EXIT_FAILURE);    }       //启用共享内存    shared_memory = shmat(shmid,(void *)0,0);    if(shared_memory == (void*)-1){        fprintf(stderr,"shmat failed\n");        exit(EXIT_FAILURE);    }       //使用共享内存    shared_stuff = (struct share_use_st *)shared_memory;    shared_stuff->written_by_you = 0;    while(running){        if(shared_stuff->written_by_you){            printf("you wrote %s",shared_stuff->some_text);            sleep(rand() % 4);             shared_stuff->written_by_you = 0;            if(strncmp(shared_stuff->some_text,"end",3) == 0){                 running = 0;            }           }       }       //共享内存被剥离    if(shmdt(shared_memory) == -1){        fprintf(stderr,"shmdt failed\n");        exit(EXIT_FAILURE);    }       //删除共享内存    if(shmctl(shmid,IPC_RMID,0) == -1){        fprintf(stderr,"shmctl(IPC_RMID) failed\n");        exit(EXIT_FAILURE);    }    exit(EXIT_SUCCESS);}

client

#include<unistd.h>#include<stdlib.h>#include<stdio.h>#include<string.h>#include<sys/shm.h>#include "shm_com.h"int main(){    int running = 1;    void *shared_memory = (void *)0;    struct share_use_st *shared_stuff;    int shmid;    char buffer[BUFSIZ];    //创建一个可读可写的共享内存    shmid = shmget((key_t)1234,sizeof(struct share_use_st),0666|IPC_CREAT);    if(shmid == -1){        fprintf(stderr,"shmget faild\n");        exit(EXIT_FAILURE);    }       //启用共享内存    shared_memory = shmat(shmid,(void *)0,0);    if(shared_memory == (void*)-1){        fprintf(stderr,"shmat failed\n");        exit(EXIT_FAILURE);    }       //使用共享内存    shared_stuff = (struct share_use_st *)shared_memory;    while(running){        while(shared_stuff->written_by_you){            sleep(1);            printf("waiting for client...\n");        }           printf("Enter some text:");        fgets(buffer,BUFSIZ,stdin);        strncpy(shared_stuff->some_text,buffer,TEXT_SZ);        shared_stuff->written_by_you = 1;        if(strncmp(buffer,"end",3) == 0){                                                                                                                                                                                                                                                 running=0;        }       }       //共享内存被剥离    if(shmdt(shared_memory) == -1){        fprintf(stderr,"shmdt failed\n");        exit(EXIT_FAILURE);    }       exit(EXIT_SUCCESS);}

这里写图片描述

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