爲什麼這會取代初始值？

Question

當我試圖解析一個文本文件，然後在單獨鏈接列表中打印內容時，每個值都由於某種原因被第二個最後一個值所覆蓋。例如，如果列表是

一個

b

Ç

d

代碼打印這些適當的線while循環內，但後來當我嘗試在代碼的末尾打印頭字符串，代碼將只爲頭和頭的下一個值打印d。

char buf[1024]; 
    printf("Enter the file name: "); 
    fgets(buf, 1024, stdin); 

    char *file_name = strtok(buf, "\n"); 
    FILE *fp; 
    fp = fopen(file_name2, "r"); 


    char *throwaway = fgets(buf, 1024, fp); 

    struct bit_t *tail; 
    struct bit_t *head; 
    head = create_node(throwaway); 
    printf("%s\n", head->pos1); 
    int count; 
    count = 0; 
    //issue is that it is just overwriting the old results 
    while((fgets(buf, 1024, fp)) != NULL) { 

      printf("String : %s\n", buf); 
      tail = insert_tail(head, create_node(buf)); 

      printf("%s\n", tail->pos1); 
    } 
    printf("Results : \n"); 
    printf("%s\n", head->pos1); 
    printf("%s\n", head->next->pos1); 

struct bit_t *create_node(char *pos1) 

{ 
     struct bit_t *r; 
     struct bit_t *current; 

    r = malloc(sizeof(struct bit_t)); 
    if(!r) { 
      exit(1); 
    } 
    r->next = NULL; 
    r->pos1 = pos1; 
    current = r; 

    return current; 

} 

struct bit_t *insert_head(struct bit_t *head, struct bit_t *node) 
{ 
     node->next = head; 
     head = node; 
     return node; 
} 
struct bit_t *insert_tail(struct bit_t *head, struct bit_t *node) 
{ 
     struct bit_t *current; 
     current = head; 
     while(current->next != NULL) { 
       current = current->next; 
     } 
     current->next = node; 

     return node;; 
} 

結構開始使用的是

struct bit_t { 
    char *pos1; 

    struct bit_t *next; 
}; 

Answer 1

每個元素在列表點buf而是通過你的循環每次迭代覆蓋的buf內容。要解決該問題，每個元素需要爲buf的內容分配存儲空間，然後複製值buf。