Linux下的C语言编程——进程间通信——内存共享

绝地灬酷狼 2022-07-14 01:39 265阅读 0赞

进程间通过共享内存来实现通信，完成父进程写入内存，子进程从内存读出并且把大写转换成小写

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <sys/types.h>
    #include <sys/ipc.h>
    #include <sys/shm.h>
    
    #define BUFFER_SIZE 2048
    
    void strupr(char *str)
    {
    	char *p;
    	
    	p = str;
    
    	while(*p != '\0')
    	{
    		if(*p >= 'A' && *p <= 'Z')
    		{
    			*p = *p + 32;
    		}
    
    		p++;
    	}
    }
    
    int main()
    {
        pid_t pid;
        int shmid;
        char *shm_addr;
        char flag[]="parent";
        char buff[BUFFER_SIZE];
        
        if((shmid = shmget(IPC_PRIVATE,BUFFER_SIZE,0666)) < 0)// ask for memery
        {
           perror("shmget");
           exit(1);
        }
        else
            printf("create share memory!\n");
        
        if((pid = fork()) < 0 )
        {
            perror("fork");
            exit(1);
        }
        else if(pid == 0)//in son process
        {
            if((shm_addr = shmat(shmid,0,0)) == (void *)-1)//鏄犲皠
            {
                perror("child:shmat\n");
                exit(1);
            }
            else 
                printf("child:Attach shared memory:%p\n",shm_addr);
    
            while(strncmp(shm_addr,flag,strlen(flag)))//鍏堝皢鏍囧織鎷峰叆鍐呭瓨
            {
                printf("child: waiting for data...\n");
                sleep(3);
            }
    
            strcpy(buff,shm_addr + strlen(flag));//鎷峰叆鍐呭瓨涓殑鏁版嵁
    		strupr(buff);
            printf("child:shared memory:%s\n",buff);
            
            if(shmdt(shm_addr) < 0)//瑙ｉ櫎鏄犲皠
            {
                perror("child:shmdt");
                exit(1);
            }
            else
                printf("child:detached shared memory\n");
        }
        else
        {
            sleep(1);
            if((shm_addr = shmat(shmid,(void *)0,0)) == (void *)-1)//鐢宠鍐呭瓨
            {
                perror("parent:shmat\n");
                exit(1);
            }
            else
            {
                printf("parent attach share memory:%p\n",shm_addr);
            }
            
            sleep(1);
            printf("input string:\n");
                
            fgets(buff,BUFFER_SIZE-strlen(flag),stdin);//杈撳叆鏁版嵁
             
    		strncpy(shm_addr+strlen(flag),buff,strlen(buff));//鎷疯礉鏁版嵁
            strncpy(shm_addr,flag,strlen(flag));//鎷疯礉鏍囧織
             
            if(shmdt(shm_addr) < 0)//瑙ｉ櫎鏄犲皠
            {
                 perror("parent:shmdt");
                 exit(1);
            }
            else
                printf("parent: deattach shared memory\n");
                
            waitpid(pid,NULL,0);//绛夊緟瀛愯繘绋嬬粨鏉?        
            if(shmctl(shmid,IPC_RMID,NULL) == -1)//鍒犻櫎鐢宠鐨勫唴瀛?        {
                perror("shmctl:IPC_RMID");
                exit(1);
            }
            else
                printf("delete shared memory\n");
             
            printf("finished!\n");
        }
    
        return 0;
    }