Getting the file size in c++

Question

I have a file and I want to get the size of the file. I can use only _wfopen or _wfopen_s for opening the file because my file path type is std::wstring.

FILE* p_file = NULL;
p_file=_wfopen(tempFileName.c_str(),L"r");
fseek(p_file,0,SEEK_END);

but I am getting an error

error C2220: warning treated as error - no 'object' file generated

This is a compilation error, you have a warning that has been treated as an error.Try to fix the warning cause or lower your warning level.this has nothing to do directly to the file opening — user18428, Mar 22 '13 at 10:25
You can get rid of warnings as beeing treated as error in this way http://stackoverflow.com/questions/2520853/warning-as-error-how-to-rid-these — banuj, Mar 22 '13 at 10:26
Can't you just use `stat`? http://msdn.microsoft.com/en-GB/library/14h5k7ff.aspx — Nick, Mar 22 '13 at 10:30
i can't use stat because i can use only file path as wstring type — mystack, Mar 22 '13 at 14:18

Nemanja Boric · Accepted Answer · 2013-03-22T10:40:18.043

To get rid of your error message, you need to fix the issue that is generating warning.

If you compile this code:

#include "stdafx.h"
#include <string>

int _tmain(int argc, _TCHAR* argv[])
{
    FILE* p_file = NULL;
    std::wstring tempFileName = L"c:\\test.txt";
    p_file=_wfopen(tempFileName.c_str(),L"r");

    if(!p_file)
    {
        perror("Open failed.");
        return 0;
    }

    fseek(p_file,0,SEEK_END);
    fclose(p_file);

    return 0;
}

You will get this warning:

warning C4996: '_wfopen': This function or variable may be unsafe. Consider using _wfopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.

So, listen what it says, and do the following:

#include "stdafx.h"
#include <string>

int _tmain(int argc, _TCHAR* argv[])
{
    FILE* p_file = NULL;
    std::wstring tempFileName = L"c:\\test.txt";
    _wfopen_s(&p_file, tempFileName.c_str(),L"r");

    if(!p_file)
    {
        perror("Open failed.");
        return 0;
    }

    fseek(p_file,0,SEEK_END);
    fclose(p_file);

    return 0;
}

There is a way to turn off this warning by putting _CRT_SECURE_NO_WARNINGS in Project Properties -> C/C++ -> Preprocessor -> Preprocessor Definitions, but you should always prefer safe alternatives to these functions.

Also, before fseek you should check if your p_file pointer is NULL.

Getting the file size in c++

1 Answers1