c - 向后读取文本文件并放入 C 中

Question

I want to know how to read a text file backwards in C.

Frozen_snowman.txt 是

Do you wanna build a snowman?
Come on lets go and play
I never see you anymore
Come out the door
It's like you've gone away-
We used to be best buddies
And now we're not
I wish you would tell me why!-
Do you wanna build a snowman?
It doesn't have to be a snowman.

代码

#include<stdio.h>
int main()
{
    int i;
    char buffer[100];
    char *a[100];
    FILE *f,*p;
    f=fopen("Frozen_snowman.txt","r");
    p=fopen("Reverse.txt","w");
    for(i=0;i<10;i++)
    {
        fgets(buffer,100,f);
        a[i]=buffer;
    }
    for(i=9;i>-1;i--)
    {
        fputs(a[i],p);
    }

    return 0;   
}

结果是

It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.
It doesn't have to be a snowman.

Why is that?

Answer 1

原因是这样的 -

fgets(buffer,100,f);       // check return of fgets
a[i]=buffer;               // Note - buffer is modified in each iteration

您指向最后一次迭代中存储在缓冲区中的字符串。每个指针都指向最后读取的字符串。每次打印时都会打印相同的字符串。

您应该做的是分配内存给指针a[i]，并使用strcpy复制字符串。