linux - C++: Getting incorrect file size

Question

I'm using Linux and C++. I have a binary file with a size of 210732 bytes, but the size reported with seekg/tellg is 210728.

I get the following information from ls-la, i.e., 210732 bytes:

-rw-rw-r-- 1 pjs pjs 210732 Feb 17 10:25 output.osr

And with the following code snippet, I get 210728:

std::ifstream handle;
handle.open("output.osr", std::ios::binary | std::ios::in);
handle.seekg(0, std::ios::end);
std::cout << "file size:" << static_cast<unsigned int>(handle.tellg()) << std::endl;

So my code is off by 4 bytes. I have confirmed that the size of the file is correct with a hex editor. So why am I not getting the correct size?

My answer: I think the problem was caused by having multiple open fstreams to the file. At least that seems to have sorted it out for me. Thanks to everyone who helped.

Answer 1

Why are you opening the file and checking the size? The easiest way is to do it something like this:

#include <sys/types.h>
#include <sys/stat.h>

off_t getFilesize(const char *path){
   struct stat fStat;
   if (!stat(path, &fStat)) return fStat.st_size;
   else perror("file Stat failed");
}

Edit: Thanks PSJ for pointing out a minor typo glitch... :)