##有名管道的应用 ###实验过程 ![实验楼](https://dn-simplecloud.shiyanlou.com/4257541496505053298-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4257541496505075312-wm) ###实验代码 fifo_write.c ``` #include #include #include #include #include #include #include #define MYFIFO "/tmp/myfifo" /* 有名管道文件名*/ #define MAX_BUFFER_SIZE PIPE_BUF /*定义在于 limits.h 中*/ int main(int argc, char * argv[]) /*参数为即将写入的字符串*/ { int fd; char buff[MAX_BUFFER_SIZE]; int nwrite; if(argc <= 1) { printf("Usage: ./fifo_write string\n"); exit(1); } sscanf(argv[1], "%s", buff); /* 以只写阻塞方式打开 FIFO 管道 */ fd = open(MYFIFO, O_WRONLY); if (fd == -1) { printf("Open fifo file error\n"); exit(1); }专业始于专注卓识源于远见 ‐ 10 ‐ /*向管道中写入字符串*/ if ((nwrite = write(fd, buff, MAX_BUFFER_SIZE)) > 0) { printf("Write '%s' to FIFO\n", buff); } close(fd); exit(0); } ``` fifo_read.c ``` #include #include #include #include #include #include #include #define MYFIFO "/tmp/myfifo" #define MAX_BUFFER_SIZE PIPE_BUF int main() { char buff[MAX_BUFFER_SIZE]; int fd; int nread; /* 判断有名管道是否已存在，若尚未创建，则以相应的权限创建*/ if (access(MYFIFO, F_OK) == -1) { if ((mkfifo(MYFIFO, 0666) < 0) && (errno != EEXIST)) { printf("Cannot create fifo file\n"); exit(1); } } /* 以只读阻塞方式打开有名管道 */ fd = open(MYFIFO, O_RDONLY); if (fd == -1) { printf("Open fifo file error\n"); exit(1); } while (1) { memset(buff, 0, sizeof(buff)); if ((nread = read(fd, buff, MAX_BUFFER_SIZE)) > 0) { printf("Read '%s' from FIFO\n", buff); } } close(fd); exit(0); } ``` ##消息队列的应用 ###实验过程 ![实验楼](https://dn-simplecloud.shiyanlou.com/4257541496566761563-wm) ###实验结果 ![实验楼](https://dn-simplecloud.shiyanlou.com/4257541496566774454-wm) ###实验代码 msgsnd.c ``` #include #include #include #include #include #include #include #define BUFFER_SIZE 512 struct message { long msg_type;//消息类型，该结构必须从这个域开始 char msg_text[BUFFER_SIZE];//消息正文 }; int main() { int qid; key_t key; struct message msg; /*根据不同的路径和关键字产生标准的key*/ if((key=ftok(".",'a'))==-1) { perror("ftok"); exit(1); } /*创建消息队列*/ if((qid=msgget(key, IPC_CREAT|0666))==-1) { perror("msgget"); exit(1); } printf("Open queue %d\n",qid); while(1) { printf("Enter some message to the queue:"); //fgets(msg.msg_text, BUFFER_SIZE, stdin) //BUFFER_SIZE读取长度 //stdin指向的文件 if((fgets(msg.msg_text, BUFFER_SIZE, stdin))==NULL) { puts("no message"); exit(1); } msg.msg_type=getpid(); /*添加消息到队列*/ /*qid ：由消息队列的标识符*/ /*msg: 消息缓冲区指针。*/ if((msgsnd(qid, &msg, strlen(msg.msg_text),0))<0) { perror("message posted"); exit(1); } if(strncmp(msg.msg_text, "quit",4)==0) { break; } } exit(0); } ``` msgrcv.c ``` #include #include #include #include #include #include #include #define BUFFER_SIZE 512 struct message { long msg_type; char msg_text[BUFFER_SIZE]; }; int main() { int qid; key_t key; struct message msg; /*根据不同的路径和关键字产生标准的key*/ if((key==ftok(".",'a'))==-1) { perror("ftok"); exit(1); } //创建消息队列 if((qid=msgget(key, IPC_CREAT|0666))==-1) { perror("msgget"); exit(1); } printf("Open queue %d\n",qid); do { //读取消息队列 memset(msg.msg_text, 0, BUFFER_SIZE); if(msgrcv(qid,(void*)&msg,BUFFER_SIZE, 0, 0)<0) { perror("msgrcv"); exit(1); } printf("The message from process %d : %s", msg.msg_type, msg.msg_text); }while(strncmp(msg.msg_text,"quit",4)); //从系统内核中移走消息队列 if((msgctl(qid,IPC_RMID,NULL))<0) { perror("msgctl"); exit(1); } exit(0); } ```

“嵌入式系统程序设计”实验报告