FILE I/O. data written at wrong location.

I got a series of functions that are connected too eachother, and that write in a certain data file, but when I look into the data file, the data entered isnt where it is supposed too be! it always writes itself in the back of the file

this is the code:

Code:

  std::ofstream WriteIt ("C:\Datacab.dat", ios::app | ios::binary );
  WriteIt.seekp ( ( (Location)* sizeof (member) ), ios::beg );
  std::cout <<"location in bytes: "<<  (Location)* sizeof (member) << std::endl;
  WriteIt.write ( ( reinterpret_cast < char * > (&Wthis) ),sizeof (member) );

I am 100% sure that somthin is wrong RIGHT THERE since this is what i got as output checking:

Code:

Location: LOOP -> 1
Registered!!
location in bytes: 0

wheras Location represents the times looped untill the place is found where the data must written, we do minus 1 (-1) to get the exact location in the file that needs too be overwritten. this is shown by : location in bytes -> 0

but it just doesnt write there! help?!
instead it just allways APPENDS on the back of the file, increasing it size too!! which isnt what i want

> std::ofstream WriteIt ("C:\Datacab.dat"
Erm, two backslashes perhaps?

> ios::app
AFAIK, if you open a file in append mode, then all writes go to the end, no matter where you've previously seeked to.

how am i supposed to write to certain locations then? ... all i know is ios::app
*edit* i have changed my program and now it writes at the right location... but i still dont know why
std::fstream WriteIt ("C:\Datacab.dat", ios::in | ios:ut | ios::binary );

Code:

#include <iostream>
#include <fstream>
using namespace std;

int main ( ) {
    ofstream f("foo.bin");
    f.write("hello",5);  // 5 chars at the start 
    f.seekp(5,ios::cur);  // a gap of 5 (will be zero filled)
    f.write("world",5);  // 5 more chars
    return 0;
}

Result
$ od -Ax -t x1z foo.bin
000000 68 65 6c 6c 6f 00 00 00 00 00 77 6f 72 6c 64     >hello.....world<
00000f

can i ask, what the diffrence between .bin files and .dat files are?
and i also solved my problem this way:

Code:

std::fstream WriteIt ("C:\Datacab.dat", ios::in | ios:ut | ios::binary );

but i can explain why that does work.

.bin, .dat, .foo, .bar, .xxx - doesn't make a bean of difference to the code.

The only thing which counts is ios::binary

Why are you still using a single \ ?

Just because \D isn't defined just makes you lucky if you're seeing "Datacab.dat" in the file system. Just try "C:\newfile.dat" and enter the land of fun.