用fwrite 想文件写入内容，用fread 将文件的内容读取出来。为什么读取到的数据总是得不到自己想要的内容，输出的时候总会有一些乱七八糟的东西

这两个函数都是处理二进制的。

具体说说是怎样读写的

只能用于二进制的读写吗

https://bbs.bccn.net/thread-476985-1-1.html

你看下这个帖子，该能解答你的问题。

# include <stdio.h>
struct person
{
    char name[32];
    int phone[11];
    char relation[32];
};
int main (void)
{
    int i;
    struct person a , b , *p2;

    FILE *p = fopen ("person.txt" , "ab+");
    if (p == 0)
        return 0;
    p2 = &a;
    scanf ("%s" , p2->name);//因为name 是字符串,首字母就是地址,p2也是一个地址,所以这里可以省略&
    for (i = 0; i < 11; i++)
        scanf ("%d" , &a.phone[i]);
    scanf ("%s" , &a.relation );//a是变量,不是指针,需要用&;
   
    while (a.phone[0] > 0)
    {
        fwrite (p2 , sizeof (struct person) , 1 , p);
        scanf ("%s" , a.name);
        for (i = 0; i < 11; i++)
            scanf ("%d" , &a.phone[i]);
        scanf ("%s" , a.relation );
    }
    fclose (p);
    FILE * fp = fopen ("person.txt" , "rb+");
    if (fp == 0)
        return 0;
    p2 = &b;
    while (!feof (fp))
    {
        fread (p2 , sizeof (struct person) , 1 , fp);
        printf ("%s " , p2->name);
        for (i = 0; i < 10; i++)
            printf ("%d" , p2->phone[i]);
        printf ("%d " , p2->phone[i]);
        printf ("%s" , p2->relation);
        printf ("\n");
    }
    fclose (fp);
    return 0;
}
为什么最后的那个数据总会输出2次啊

# include <stdio.h>
struct person
{
    char name[32];
    int phone[11];
    char relation[32];
};
int main (void)
{
    int i;
    struct person a;
    FILE *fp = fopen ("person.txt" , "ab+");
    if (fp == 0)
        return 0;
    scanf ("%s" , a.name);
    for (i = 0; i < 11; i++)
        scanf ("%d" , &a.phone[i]);
    scanf ("%s" , a.relation );
    if (a.phone[0] > 0)
    {
        fwrite (&a, sizeof (struct person) , 1 , fp);
    }
    fclose (fp);
    fp = fopen ("person.txt" , "rb");
    if (fp == 0)
        return 0;
    while (fread (&a, sizeof (struct person) , 1 , fp)==1)
    {
        printf ("%s " , a.name);
        for (i = 0; i < 10; i++)
            printf ("%d " , a.phone[i]);
        printf (" %s\n" , a.relation);
    }
    fclose (fp);
    return 0;
}

受教了

为什么不能用feof函数来判断文件的结尾呢

只要用feof函数判断文件结尾,最后输出就会多一个
while (!feof (fp))
    {
        fread (&a, sizeof (struct person) , 1 , fp);
        printf ("%s " , a.name);
        for (i = 0; i < 10; i++)
            printf ("%d" , a.phone[i]);
        printf ("%d " , a.phone[i]);
        printf (" %s\n" , a.relation);
    }
最后的一个会重复是什么原因啊