###首先测试有名管道### 编写`fifo_write.c`如下: ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496449058960-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496449594382-wm) 编写`fifo_read.c`如下: ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450136371-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450691265-wm) 如图，我们现在有两个可执行文件了。一个是`fr`,`fw`要开两个进程的通信。所以我们要打开另一个标签，一个执行读，一个执行写 ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450715490-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450825327-wm) 读取之前： ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450854813-wm) 我们写入了3组数据： ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450943864-wm) 下面我们看另一个标签有没有接收到： ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496450966544-wm) 因为它是以只读阻塞方式打开，在没有写入之前，它会一致阻塞，就如图中光标一直闪烁。 /* 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; //定义变量 char buff[MAX_BUFFER_SIZE]; int nwrite; if(argc <= 1) //如果接收参数个数小于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); } /*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" /* 有名管道文件名*/ #define MAX_BUFFER_SIZE PIPE_BUF /*定义在于 limits.h 中*/ 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); //打开有名管道以只读的方式 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); } ###测试消息队列### 编写发送端 `msgsnd.c`并编译 ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496456621310-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496457677271-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496457754159-wm) 编写接收端`msgrcv.c`并编译 ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496458133918-wm) ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496458443602-wm) 消息传达过程： ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496459703189-wm) 分别发送了 2014 ，wuhongwei 和2014025641 3条信息 ![实验楼](https://dn-simplecloud.shiyanlou.com/4225551496459742803-wm) /* msgsnd.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); while(1) { printf("Enter some message to the queue:"); if ((fgets(msg.msg_text, BUFFER_SIZE, stdin)) == NULL) { puts("no message"); 姜先富 2017/6/10 8:33:54 exit(1); } msg.msg_type = getpid(); /*添加消息到消息队列*/ 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); 姜先富 2017/6/10 8:34:10 } /*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