Question

我正在学习用C编程，我正在开展一个小项目：图书馆管理软件。我遇到的问题是使搜索功能起作用。我知道如果我处理大量数据，我的代码非常简单且效率低下，但由于情况并非如此，我认为它应该可行。这是我写的函数：

void search_for_book (FILE *BooksFile) {
    BooksFile = fopen("Data.txt", "a+");

    char book_title[100], test_book[100], author[100], category[100];
    int answer, status, more_books;

    more_books: // To search for more books

    printf("Type the title of the book you would like to look for:\n");
    scanf("%s", book_title);

    while(!feof(BooksFile)){
        fscanf(BooksFile, "%s", test_book);

        if(strcmp(book_title, test_book) == 0) { // strcmp returns zero if strings are equal
            printf("The book you informed was found.\n");
            printf("Do you want to see its information? Type 1 for yes and 2 for no.\n");
            scanf("%d", &answer);

            if (answer == 1) { // User wants information
                fscanf(BooksFile, "%s", author);
                fscanf(BooksFile, "%s", category);
                fscanf(BooksFile, "%d", &status);

                printf("Book's title: %s\n", book_title);
                printf("Book's author: %s\n", author);
                printf("Book's category: %s\n", category);
                printf("Book's status: %d\n", status);

                break;

            } else { // User doesn't want information
                printf("Would you like to search for another book? Type zero if that's the case.\n");
                scanf("%d", &more_books);

                if (more_books == 0) {
                    goto more_books;
                }

                break;
            }
        }
    } 
}

我的代码有什么问题，我该如何解决？当我调用这个函数时，程序只执行printf（要求输入书的标题），然后简单地返回主函数，而不是搜索任何东西。

Answer 1

用“r”而不是“a +”打开文件，+是用于追加和文件的结尾，你没有写入它。
看起来您的文件包含标题，作者，类别和状态，当您搜索所有行时，您可能会在作者行中找到您要查找的文本。即使您不需要，也要阅读每本书的所有数据。
当您返回more_books时，不会回滚文件。尝试fseek（0，SEEK_SET）。或者关闭/重新打开文件。
键入以通过for循环替换goto，它更容易阅读（尽管goto不受欢迎但有效）。

Answer 2

你的代码似乎效率低下，我不知道为什么你在search_for_book函数中传递文件指针而不是你可以在本地使用并打开它。我已经对你的功能做了一些修改试试吧。

void search_for_book() 
{
    FILE *BooksFile;

    BooksFile = fopen("Data.txt", "r");

    char book_title[100], test_book[100], author[100], category[100];
    int answer, status, more_books;

    while(1)
    {
        printf("Type the title of the book you would like to look for:\n");
        scanf("%s", book_title);

        while(!feof(BooksFile))
        {
            fscanf(BooksFile, "%s", test_book);

            if(strcmp(book_title, test_book) == 0) 
            { 
                printf("The book you informed was found.\n");
                printf("Do you want to see its information? Type 1 for yes and 2 for no.\n");
                scanf("%d", &answer);

                if (answer == 1) 
                { 
                    // User wants information
                    fscanf(BooksFile, "%s", author);
                    fscanf(BooksFile, "%s", category);
                    fscanf(BooksFile, "%d", &status);

                    printf("Book's title: %s\n", book_title);
                    printf("Book's author: %s\n", author);
                    printf("Book's category: %s\n", category);
                    printf("Book's status: %d\n", status);
                    break;
                } 

            }
        } 

        rewind(BooksFile);
        printf("Would you like to search for another book? Type zero if that's the case.\n");
        scanf("%d",&more_books);

        if(more_books == 1)
         continue;
        else
          break;
    }
}

在C中简单搜索文件

2 个答案: