从文件中读取结构体变量的数据读取和写入结构体数据到文件

#include <stdio.h>

size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);

size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream);

struct A{    int a;    int b;    char c;    double d;};void freadtest(){    struct A tmp,test;    tmp.a =1;    tmp.b= 2;    tmp.c = 'a';    tmp.d = 1.235;    FILE *fd = fopen("a1.txt","a+");    if(fd == NULL)        cout<<"open fail"<<endl;    cout<<fread(&test,sizeof(tmp),1,fd)<<endl;    cout<<fwrite(&tmp,sizeof(tmp),1,fd)<<endl;   cout<<test.c<<endl;    fclose(fd);    cout<<getlogin()<<endl;}int main(){    cout<<"=====fread_fwriteTest======"<<endl;    freadtest();    return 1;}