在 C 中简单搜索文件

Question

我正在学习用 C 编程，并且正在做一个小项目：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，但既然情况并非如此，我认为它应该可以工作。 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（要求输入书名），然后简单地返回主函数，不搜索任何内容。

Answer 1

您的代码似乎效率低下，我不知道您为什么在 search_for_book 函数中传递文件指针，而不是您可以在本地获取并使用它打开。我对你的函数做了一些修改，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;
    }
}

Answer 2

• 用“r”而不是“a+”打开文件，a+ 用于追加和文件末尾，您没有写入文件。
• 看起来您的文件包含标题、作者、类别和状态，当您搜索时您阅读了所有行，因此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，您不会倒带文件。尝试 fseek(0, SEEK_SET)。或关闭/重新打开文件。
• 键入用 for 循环替换 goto，它更易于阅读（虽然 goto 不受欢迎但有效）。