How can I get the length of a file in C++?

Question

Hi!

How can I get the length of a file in C++?
I have wrote this:

long length(string filename)
{
long tor = 0;
char c;
ifstream von(filename);
while(von.get(c))
tor++;
return tor;
}

But it doesn't work if the file named filename is e.g. a picture (.png, .jpg, etc.)

Can someone tell me why?

Hope I will get some answers,
S.A.

Answer 1

Sure you can iterate through a png. Even an exe, db and anything else.
They are all just files with a bunch of characters in the end.

But you have to open the file in binary mode to correctly read from them like:
std::ifstream von( filename, std::ios_base::in | std::ios_base::binary );

If your compiler supports filesystem you can just use
std::filesystem::file_size( path )
to get the file size.

Another way you can do it is by simply ignoring everything in the file with
file.ignore( std::numeric_limits<std::streamsize>::max() );
and then reading file's gcount with
std::streamsize length = file.gcount();
( You may need to include <limits> for this one )

But, this also requires the file to be opened in binary mode.