Deleting the contents of the file not working

Deleting the contents of the file not working

I'm writing, reading and deleting the content of a file. Eeverything works
fine except the delete part, as when i press y it says deleted but doesn't
display any records.
typedef struct ch
{
char str[10];
};
void disp(ch d)
{
cout<<"\n"<<d.str<<"\n";
}
//delete part
cout<<"\nwant to delete??";
char c;
cin>>c;
if(c=='y')
{
char s[10];
cout<<"nter - ";
cin>>s;
file.seekg(0);
int found=0;
fstream temp("temp.dat",ios::in|ios::out|ios::app);
while(file.read((char *)&dta,sizeof(dta)))
{
if(strcmp(dta.str,s)==0)
{
found=1;
cout<<"deleted";
}
else
temp.write((char *)&dta,sizeof(dta));
}
if(!found)
cout<<"not found";
remove("new.dat");
rename("temp.dat","new.dat");
temp.close();
file.open("new.dat",ios::in|ios::out|ios::app);
}