Trying to write a simple program that will read data but keep stumbling upon the fact that I kinda can't limit the amount that is read.
I have simple student.dat file which is filled ATM with nothing else but simple string "somethinginside", without quotes.
When I do this on each cout it outputs whole file plus several weird chars.

#include <iostream>
#include <fstream>

struct students
{
  char name[7];
  char lastname[15];
};

int main()
{
   int input(0); //for pause later
   students data;
   std::fstream dat ("student.dat", std::ios::in | std::ios::binary); //opens file for read
   dat.read ((char *) &data, sizeof(data)); //should read data
   std::cout << "name " << data.name << std::endl; //outputs more than it should
   std::cout << "lastname " << data.lastname << std::endl; //outputs more than it should
   dat.close(); // closes
   std::cin >> input; //pause to see output
   return true;
}

If I try adding this one after reading

std::fstream dt ("something.dat",std::ios::out | std::ios::binary);
dt.write (data.name, 10);
dt.close();

it will output "somethingi", while I'm pretty sure, I hope, that I defined it's length in structure and when reading how much to read.

I get same even if I try reading it with

dat.read (data.name, sizeof(data.name));

I'd be grateful for any helpful advice :)

Most likely your strings aren't being terminated with '\0'. What does the file look like?

Most likely your strings aren't being terminated with '\0'. What does the file look like?

Simple new text file, rename to student.dat, edit with notepad++, wrote "somethinginside", without quotes and that's it.

Though, I got an impression that it should just read block with size that is specified, not more, regardless of how string ends.

Only other option that I stumbled upon is to read data using get, though then I end up reading studet.name and student.lastname instead of just student.

So the problem is something of a misunderstanding of C-style strings. I'd recommend not using read and write (in general, actually, because they're only safe for POD types) and read each data member individually:

//dat.read ((char *) &data, sizeof(data)); //should read data
dat.get(data.name, sizeof data.name);
dat.get(data.lastname, sizeof data.lastname);

Thank you, I'll try with that one :)