c - C语言中使用fgets()逐行读取文件

Question

因此，我正在努力让我的程序逐行读取文件，并将每一行(作为“字符串”)存储到链接列表中。

下面的 while 循环

FILE *f;
char string[longest];
while(fgets (string, longest, f) != NULL) {    //Reading the file, line by line
    printf("-%s", string);    //Printing out each line
    insert(file_list, string);  //Why does it not change?
}

printf() 函数按预期工作，打印出每一行。我用连字符作为测试，看看它是否会在行之间分开。但是，当将“字符串”插入链表时，只会多次插入第一个字符串。

例如，假设我有一条文本:

Roses are red,
Violets are blue,
Sugar is sweet,
And so are you.

现在，当读取这个文件并打印出结果时，我得到:

-Roses are red,
-Violets are blue,
-Sugar is sweet,
-And so are you.

但是，当打印链接列表时，我没有得到相同的结果，而是得到:

Roses are red,
Roses are red,
Roses are red,
Roses are red,

有谁知道为什么 while 循环中的“string”变量在将其插入链表时每次迭代后都不会改变？它只插入第一行四次。

我错过了什么？

更新:我的插入代码如下:

void insert(node_lin *head, char *dataEntry) {
    node_lin * current = head;

    if(current->data == NULL) {
        current->data= dataEntry;
        current->next = NULL;
    }

    else {
        while(current->next != NULL) {
            current = current->next;
        }

        current->next = malloc(sizeof(node_lin));
        current->next->data = dataEntry;
        current->next->next = NULL;
    }
}

Answer 1

插入代码不正确。需要首先使用malloc()并将字符串strcpy写入node的数据中。这里您只是复制指针。

void insert(node_lin *head, char *dataEntry) {
    node_lin * current = malloc(sizeof(node_lin));
    node_lin *p = NULL;

    /*make sure that an empty list has head = NULL */
    if(head == NULL) { /*insert at head*/
        strcpy(current->data, dataEntry);
        current->next = NULL;
        head = current;
    } else {
        p = head;
        while(p->next != NULL) {
            p = p->next;
        }
        /*insert at tail*/
        p->next = current;
        strcpy(current->data, dataEntry);
        current->next = NULL;
    }  
}