c - 我试图通过从文件中读取它来创建链接列表

Question

这个问题已经有答案了:

Why is “while( !feof(file) )” always wrong? (5 个回答)

已关闭 3 年前。

#include <stdio.h>
#include <stdlib.h>
#define NULL 0

struct student
{
    int id;
    char name[20];
    float marks;
    struct student *next
};
typedef struct student node;
void main()
{
    node *head;
    void read(node *p);
    void create(node *p);
    int count(node *p);
    void print(node *p);
    head=(node *)malloc(sizeof(node));
    read(head);

}
void read(node *list)
{
    FILE *fp;
    char filename[30];
    int i;
    printf("input file name:");
    scanf("%s",filename);
    fp=fopen(filename,"r");

    while(!feof(fp))
    {
        create_f(list,fp);
    }

}
void create_f(node *list,FILE *fp )
{
    fscanf(fp,"%s %d %f",
               list->name,&list->id,&list->marks);
    printf("%s \t%d \t%f\n",
                        list->name,list->id,list->marks);

   list->next=(node*)malloc(sizeof(node));
    return;
}

应该读取的文件是这样的:
但由于某些原因它读取了最后一行两次。有人可以帮助我吗？

如果您无法打开它，则输出为:

input file name:input.txt.txt
student01 1 95.000000
student03 3 90.000000
student05 5 86.000000
student07 7 83.000000
student09 9 98.000000
student10 10 93.000000
student08 8 92.000000
student06 6 96.000000
student04 4 93.000000
student02 2 88.000000
student02 2 88.000000

Process returned 16 (0x10) execution time : 4.043 s Press any key to continue.

1 :

Answer 1

因此，代码中的主要错误已经在几个答案中得到了很好的解释，请查看以下链接:

1. feof
2. fscanf

以下代码片段应该可以解决您的问题，请注意，我只有一个函数。

输入(input.txt)

student01 1 95.000000
student03 3 90.000000
student05 5 86.000000
student07 7 83.000000
student09 9 98.000000
student10 10 93.000000
student08 8 92.000000
student06 6 96.000000
student04 4 93.000000
student02 2 88.000000

解决方案

#include <stdio.h>
#include <stdlib.h>

struct student {
    int id;
    char name[20];
    float marks;
    struct student *next;
};
typedef struct student node;

void read(node *list) {
    FILE *fp;
    char filename[30];
    printf("input file name: ");
    scanf("%s",filename);
    fp=fopen(filename,"r");

    if(fp == NULL) return; // file doesn't exist

    while(fscanf(fp, "%s %d %f", list->name, &list->id, &list->marks) == 3) {
        printf("%s \t%d \t%f\n", list->name,list->id,list->marks);

        list->next=(node*)malloc(sizeof(node));
     }
    fclose(fp);
}

int main() {
    node *head; 
    head=(node *) malloc(sizeof(node));
    read(head); 
    return 0;
}

输出

input file name: input.txt
student01   1   95.000000
student03   3   90.000000
student05   5   86.000000
student07   7   83.000000
student09   9   98.000000
student10   10  93.000000
student08   8   92.000000
student06   6   96.000000
student04   4   93.000000
student02   2   88.000000