Question

程序似乎有效，但无法弄清楚为什么它没有运行第二部分代码。例如，当我编译并执行msg2.cpp时，它会提示用户“输入一些文本”。当用户输入文本时，msg1.cpp显示用户输入。问题是msg1.cpp没有提示用户'输入一些文字'。关于我如何接收和发送消息的任何建议？

//msg2.cpp
/* The sender program is very similar to msg1.cpp. In the main set up, delete the
 msg_to_receive declaration and replace it with buffer[BUFSIZ], remove the message
 queue delete and make the following changes to the running loop.
 We now have a call to msgsnd to send the entered text to the queue. */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>

#define MAX_TEXT 512

struct my_msg_st {
    long int my_msg_type;
    char some_text[MAX_TEXT];
};

int main()
{
    int running = 1;
    struct my_msg_st some_data;
    int msgid;
    char buffer[BUFSIZ];
    long int msg_to_receive = 0;

    msgid = msgget((key_t)1234, 0666 | IPC_CREAT);

    if (msgid == -1) {
        fprintf(stderr, "msgget failed with error: %d\n", errno);
        exit(EXIT_FAILURE);
    }

    while(running) {
        printf("Enter some text: ");
        fgets(buffer, BUFSIZ, stdin);
        some_data.my_msg_type = 1;
        strcpy(some_data.some_text, buffer);

        if (msgsnd(msgid, (void *)&some_data, MAX_TEXT, 0) == -1) {
            fprintf(stderr, "msgsnd failed\n");
            exit(EXIT_FAILURE);
        }
        if (strncmp(buffer, "end", 3) == 0) {
            running = 0;
        }
    }

    /* Then the messages are retrieved from the queue, until an end message is encountered.
 Lastly, the message queue is deleted. */

    while(running) {
        if (msgrcv(msgid, (void *)&some_data, BUFSIZ,
                   msg_to_receive, 0) == -1) {
            fprintf(stderr, "msgrcv failed with error: %d\n", errno);
            exit(EXIT_FAILURE);
        }
        printf("You wrote: %s", some_data.some_text);
        if (strncmp(some_data.some_text, "end", 3) == 0) {
            running = 0;
        }
    }

    if (msgctl(msgid, IPC_RMID, 0) == -1) {
        fprintf(stderr, "msgctl(IPC_RMID) failed\n");
        exit(EXIT_FAILURE);
    }

    exit(EXIT_SUCCESS);
}

//msg1.cpp
/* Here's the receiver program. */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>

#define MAX_TEXT 512
//string UserInput(string);

struct my_msg_st {
    long int my_msg_type;
    char some_text[BUFSIZ];
    //char some_text[MAX_TEXT];
};

int main()
{
    int running = 1;
    int msgid;
    struct my_msg_st some_data;
    long int msg_to_receive = 0;
    char buffer[BUFSIZ];
    char some_text[MAX_TEXT];
    //string input;

/* First, we set up the message queue. */

    msgid = msgget((key_t)1234, 0666 | IPC_CREAT);

    if (msgid == -1) {
        fprintf(stderr, "msgget failed with error: %d\n", errno);
        exit(EXIT_FAILURE);
    }
/* Then the messages are retrieved from the queue, until an end message is encountered.
 Lastly, the message queue is deleted. */

    while(running) {
        if (msgrcv(msgid, (void *)&some_data, BUFSIZ,
                   msg_to_receive, 0) == -1) {
            fprintf(stderr, "msgrcv failed with error: %d\n", errno);
            exit(EXIT_FAILURE);
        }
        printf("You wrote: %s", some_data.some_text);
        if (strncmp(some_data.some_text, "end", 3) == 0) {
            running = 0;
        }
    }

    if (msgctl(msgid, IPC_RMID, 0) == -1) {
        fprintf(stderr, "msgctl(IPC_RMID) failed\n");
        exit(EXIT_FAILURE);
    }

    // Need to reset value, before entering second loop 
    // At this point, value enters loop, prompts user enter text
     while(running) {
        printf("Enter some text: ");
        for (int i = 1; i < running; i++){
        fgets(buffer, BUFSIZ, stdin);
        some_data.my_msg_type = 1;
        strcpy(some_data.some_text, buffer);
        }
        if (msgsnd(msgid, (void *)&some_data, MAX_TEXT, 0) == -1) {
            fprintf(stderr, "msgsnd failed\n");
            exit(EXIT_FAILURE);
        }
        if (strncmp(buffer, "end", 3) == 0) {
            running = 0;
        }
    }

    exit(EXIT_SUCCESS);
}

Answer 1

我的.02货币单位来自msg1.cpp：

if (msgctl(msgid, IPC_RMID, 0) == -1) {
        fprintf(stderr, "msgctl(IPC_RMID) failed\n");
        exit(EXIT_FAILURE);
    }

您似乎只要在＆＃39;结束时立即删除邮件队列。消息已收到。

（另外：fprintf()＆C ++程序中的朋友？）

程序无法接收和发送

1 个答案: