c - 请告诉我我的错误

Question

这段代码应该“打开”输入的保存的txt文件，并且可以由用户编辑......

例如，我在 save.txt 中保存了“Bob 12345 17”和“Max 123456 18”...当我打开文件文件并打印链接列表中的所有内容时，它只显示:“Max 123456 18”。 ..每当我关闭程序并尝试先打开 save.txt 而不覆盖它时，当我在链接列表中打印所有内容时，它不会显示任何内容...

FILE* open;
char filenameopen[100];

printf ("\nType the name of the file you want to open: ");
scanf ("%s", filenameopen);
printf ("\n");

open = fopen (filenameopen, "r");
if (filenameopen == NULL)
    printf ("No such file exists\n\n");
else
{   
    phonebook_t *openentry = (phonebook_t*) malloc (sizeof(phonebook_t));
    openentry = head;

    while (1)
    {
        fscanf (open, "%s %s %d", openentry -> name, openentry -> tel, &openentry -> age);
        if (feof (open))
        {
            openentry -> next = NULL;
            break;
        }
        openentry -> next = (phonebook_t*) malloc (sizeof(phonebook_t)); 
        openentry = openentry -> next;  
    }

    fclose(open);
}

Answer 1

看起来在您的 while 循环中，当您将链表分配给下一个节点时，您会丢失链表的头部......所以您将无法打印完成循环后，将显示整个列表。

将您的代码调整为如下所示:

//declare you head-pointer outside the scope of the if-statement
phonebook_t *ll_head = (phonebook_t*) malloc (sizeof(phonebook_t));

if (...)
{
    //...
}
else
{
    //assign a temporary pointer to use in your while-loop
    phonebook_t* openentry = ll_head;

    //...rest of your code
}

现在，完成 while 循环后，从 ll_head 开始打印，因为它仍然指向链表的开头，而不是最后一个节点。