c - 如何将字符串从文件传递到链表

Question

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
struct ll
{
    char data[50];
    struct ll *next;
    struct ll *prev;
};
typedef struct ll node;

main()
{
    node *head;node *temp1;node *temp2;
    head = (node *)malloc(sizeof(node));
    temp1 = head;
    FILE *p;
    int n;
    char s[50];
    p = fopen("studentRecords.txt","r");
    while((fscanf(p, "%s", s)) != EOF)
    {
        strcpy(head->data, s);
        head->next = (node *)malloc(sizeof(node));
        head->next = head->next->prev;
        head = head->next;
    }
    head = NULL;
    fclose(p);
    for(temp2 = temp1; temp2->next != NULL; temp2 = temp2->next)
        printf("%s\n", temp2->data);
}

当我运行上面的代码时，输​​出是一个段错误。我该如何纠正这个问题？我将学生的记录作为字符串保存在 studentRecords.txt 文件中。

Answer 1

您在初始化之前使用 next:

head->next = (node *)malloc(sizeof(node));
head->next = head->next->prev;             /* head->next->prev is garbage. */
head = head->next;                         /* Now `head` points nowhere. */

稍后您将取消引用该垃圾值。此外，您正在覆盖刚从 malloc 获得的内存。