Overwriting a record in a binary file

Hi, here I am trying to overwrite a record in a binary file, however it overwrites the entire file with the write function.  I have attempted to use ios::trunc in the fstream constructor, but still produces same result.

*in this example code i'm simply trying to overwrite the first record, I can retrieve this.

fstream f("records.bin", ios::binary | ios::out);
 
f.seekp(0);
f.write(reinterpret_cast<const char*>(&binPerson),sizeof(binPerson));
f.close();

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