Linux下創建共享內存和測試

/*
This is shdata.h
Founded In Others's Blog. Thanks For Sharing Your Knowledge
*/
#ifndef _SHMDATA_H_HEADER  
#define _SHMDATA_H_HEADER  
#define TEXT_SZ 2048  
  
struct shared_use_st  
{  
    int written;//作爲一個標誌，非0：表示可讀，0表示可寫  
    char text[TEXT_SZ];//記錄寫入和讀取的文本  
};  
#endif 

/

/*
	This is shm_read.c . For read sharing-memory
	Founded In Others's Blog. Thanks For Sharing Your Knowledge	
*/
#include <unistd.h>  
#include <stdlib.h>  
#include <stdio.h>  
#include <sys/shm.h>  
#include "shdata.h"  
  
int main()  
{  
    int running = 1;//程序是否繼續運行的標誌  
    void *shm = NULL;//分配的共享內存的原始首地址  
    struct shared_use_st *shared;//指向shm  
    int shmid;//共享內存標識符  
    //創建共享內存  
    shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);  
    if(shmid == -1)  
    {  
        fprintf(stderr, "shmget failed\n");  
        exit(EXIT_FAILURE);  
    }  
    //將共享內存連接到當前進程的地址空間  
    shm = shmat(shmid, 0, 0);  
    if(shm == (void*)-1)  
    {  
        fprintf(stderr, "shmat failed\n");  
        exit(EXIT_FAILURE);  
    }  
    printf("\nMemory attached at %X\n", (int)shm);  
    //設置共享內存  
    shared = (struct shared_use_st*)shm;  
    shared->written = 0;  
    while(running)//讀取共享內存中的數據  
    {  
        //沒有進程向共享內存定數據有數據可讀取  
        if(shared->written != 0)  
        {  
            printf("You wrote: %s", shared->text);  
            sleep(rand() % 3);  
            //讀取完數據，設置written使共享內存段可寫  
            shared->written = 0;  
            //輸入了end，退出循環（程序）  
            if(strncmp(shared->text, "end", 3) == 0)  
                running = 0;  
        }  
        else//有其他進程在寫數據，不能讀取數據  
            sleep(1);  
    }  
    //把共享內存從當前進程中分離  
    if(shmdt(shm) == -1)  
    {  
        fprintf(stderr, "shmdt failed\n");  
        exit(EXIT_FAILURE);  
    }  
    //刪除共享內存  
    if(shmctl(shmid, IPC_RMID, 0) == -1)  
    {  
        fprintf(stderr, "shmctl(IPC_RMID) failed\n");  
        exit(EXIT_FAILURE);  
    }  
    exit(EXIT_SUCCESS);  
} 

/*
 	This is shm_write.c
	Founded In Others's Blog. Thanks For Sharing Your Knowledge	
*/
  #include <unistd.h>  
    #include <stdlib.h>  
    #include <stdio.h>  
    #include <string.h>  
    #include <sys/shm.h>  
    #include "shdata.h"  
      
    int main()  
    {  
        int running = 1;  
        void *shm = NULL;  
        struct shared_use_st *shared = NULL;  
        char buffer[BUFSIZ + 1];//用於保存輸入的文本  
        int shmid;  
        //創建共享內存  
        shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);  
        if(shmid == -1)  
        {  
            fprintf(stderr, "shmget failed\n");  
            exit(EXIT_FAILURE);  
        }  
        //將共享內存連接到當前進程的地址空間  
        shm = shmat(shmid, (void*)0, 0);  
        if(shm == (void*)-1)  
        {  
            fprintf(stderr, "shmat failed\n");  
            exit(EXIT_FAILURE);  
        }  
        printf("Memory attached at %X\n", (int)shm);  
        //設置共享內存  
        shared = (struct shared_use_st*)shm;  
        while(running)//向共享內存中寫數據  
        {  
            //數據還沒有被讀取，則等待數據被讀取,不能向共享內存中寫入文本  
            while(shared->written == 1)  
            {  
                sleep(1);  
                printf("Waiting...\n");  
            }  
            //向共享內存中寫入數據  
            printf("Enter some text: ");  
            fgets(buffer, BUFSIZ, stdin);  
            strncpy(shared->text, buffer, TEXT_SZ);  
            //寫完數據，設置written使共享內存段可讀  
            shared->written = 1;  
            //輸入了end，退出循環（程序）  
            if(strncmp(buffer, "end", 3) == 0)  
                running = 0;  
        }  
        //把共享內存從當前進程中分離  
        if(shmdt(shm) == -1)  
        {  
            fprintf(stderr, "shmdt failed\n");  
            exit(EXIT_FAILURE);  
        }  
        sleep(2);  
        exit(EXIT_SUCCESS);  
    }