修改文件内容

void CfileTestDlg::OnBnClickedButton1()
{

struct student
{
char name [96];
int   nId ;
char  desc[1024];

};

FILE *fp = fopen("D:\\20080507.log ", "rb+");

if (fp==0)
{
printf("can't open file\n");
return ;
}

char szBuf[4096];
memset (szBuf,0,sizeof(szBuf));
struct student   stud;
stud.nId  = 96;
memcpy(stud.name,"iqaeuqioweuqeruurururuu89999999999999",strlen("iqaeuqioweuqeruurururuu8888888888"));

memcpy(szBuf, &stud, sizeof(student));

fseek(fp, 0, SEEK_SET);

fwrite(szBuf, 4096, 1, fp);
fflush(fp);
fclose(fp);
return ;
}

void CfileTestDlg::OnBnClickedButton2()
{
// TODO: Add your control notification handler code here
struct student
{
char name [96];
int   nId ;
char  desc[1024];

};

FILE *fp = fopen("D:\\20080507.log ", "a+");

if (fp==0)
{
printf("can't open file\n");
return ;
}

char szBuf[4096];
memset (szBuf,0,sizeof(szBuf));
struct student   stud;
stud.nId  = 96;
memcpy(stud.name,"iqaeuqioweuqeruurururuu8888888888",strlen("iqaeuqioweuqeruurururuu8888888888"));

memcpy(szBuf, &stud, sizeof(student));

fseek(fp, 0, SEEK_END);

fwrite(szBuf, 4096, 1, fp);

fwrite(szBuf, 4096, 1, fp);

fflush(fp);
fclose(fp);
return ;
}