Help with file handling

From C++ language point of view, you can only try to open the file and see if that works. If it doesn't however, there can be multiple reasons (file does not exist, permission denied, ...).

To really check if a file exists, you need to use OS specific functions. Unfortunately you do not tell in your post, what OS you are using, so I cannot help you further.

Unfortunately theres no FileExists function or soemthing similar (at least none I know of). You can try to query its attributes and check if the operation fails. If it fails you have to check the error code against ERROR_FILE_NOT_FOUND to know why the call failed.

#include <windows.h>

bool FileExists( LPCTSTR strFileName ) // or std::string / CString
{
if( 0xffffffff == ::GetFileAttributes( strFileName ) )
{
// failure, determine why it failed
if( ERROR_FILE_NOT_FOUND == ::GetLastError() )
{
// file doesnt exist
return false;
}
}
return true;
}

I'm using windows.
You can use FindFirstFile ( http://msdn2.microsoft.com/en-us/library/Aa364418.aspx) to see if a file exists. Upon success (file found), the function will also tell you the size of the file.

u can try this function _access(). this function takes 2 parameters file path and flag. flag is 0 for checking the existence of the file.

Just curious... why use a windows-specific function when

std::ifstream testFile("file.txt");
if(testFile.fail()) /* File doesn't exist. */

will work just as well? Honestly, if you can't open it, it's as good as not there...

Otherwise, you can just open the file for read/write in append mode, then use the tellg method to determine the size of the file. Note that this will create the file if it doesn't exist, but the OP sounds like that's exactly what he wants to do.

Cheers,
Zen

How about "File not found or permission denied." :)
Alright, I'll admit that using tellg to determine if the file was originally empty is the better option, especially based on the OP's requirements.
Cheers,
Zen