linux 共享内存 sys-V函数类型

#ifndef _SHMDATA_H_HEADER
#define _SHMDATA_H_HEADER
#define TEXT_SZ 2048
struct shared_use_st
{
            int written;//作为一个标志，非0：表示可读，0表示可写 
            char text[TEXT_SZ];//记录写入和读取的文本
};
#endif

include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/shm.h>
#include "shmdata.h"
int main()
{
        int running = 1;
        void *shm = NULL;
        struct shared_use_st *shared = NULL;
        char buffer[BUFSIZ + 1];//用于保存输入的文本
        int shmid;  //创建共享内存
        shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);
        if(shmid == -1)
        {
                fprintf(stderr, "shmget failed\n");
                exit(EXIT_FAILURE);
        }   //将共享内存连接到当前进程的地址空间
        shm = shmat(shmid, (void*)0, 0);
        if(shm == (void*)-1)
        {
                fprintf(stderr, "shmat failed\n");
                exit(EXIT_FAILURE);
        }
        printf("Memory attached at %p\n", shm);    //设置共享内存   
        shared = (struct shared_use_st*)shm;
        while(running)//向共享内存中写数据  
        {       //数据还没有被读取，则等待数据被读取,不能向共享内存中写入文本       
                while(shared->written == 1)
                {
                        //sleep(1);      
                        //printf("Waiting...\n");
                }       //向共享内存中写入数据       
                printf("Enter some text: ");
                fgets(buffer, BUFSIZ, stdin);
                strncpy(shared->text, buffer, TEXT_SZ); //输入了end，退出循环（程序）       
                shared->written = 1;     // 
                if(strncmp(buffer, "end", 3) == 0)
                        running = 0;
        }   
        if(shmdt(shm) == -1) //把共享内存从当前进程中分离
        {
                fprintf(stderr, "shmdt failed\n");
                exit(EXIT_FAILURE);
        }
        sleep(2);
        exit(EXIT_SUCCESS);
}

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/shm.h>
#include "shmdata.h"
int main()
{
        int running = 1;//程序是否继续运行的标志  
        void *shm = NULL;//分配的共享内存的原始首地址   
        struct shared_use_st *shared;//指向shm   
        int shmid;//共享内存标识符 //创建共享内存   
        shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);
        if(shmid == -1)
        {
                fprintf(stderr, "shmget failed\n");
                exit(EXIT_FAILURE);
        }   //将共享内存连接到当前进程的地址空间
        shm = shmat(shmid, 0, 0);
        if(shm == (void*)-1)
        {
                fprintf(stderr, "shmat failed\n");
                exit(EXIT_FAILURE);
        }
        printf("\nMemory attached at %p\n", shm);  //设置共享内存   
        shared = (struct shared_use_st*)shm;
        shared->written = 0;
        while(running)//读取共享内存中的数据 
        {       //没有进程向共享内存定数据有数据可读取       
                if(shared->written != 0)
                {
                        printf("You wrote: %s", shared->text);
                        sleep(rand() % 3);          //读取完数据，设置written使共享内存段可写
                        shared->written = 0;         //输入了end，退出循环（程序）  
                        if(strncmp(shared->text, "end", 3) == 0)
                                running = 0;
                }
                else//有其他进程在写数据，不能读取数据     
                        sleep(1);
        }   //把共享内存从当前进程中分离
        if(shmdt(shm) == -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);
}