Thread: Using filebuf::sh_read

Ok, I think I've posted this question before but it never got replied to. My problem is that I want to open a file with read and write sharing, using a std::ifstream, but I can't. I've seen in about 99999 places on the web, tutorials, books, MSDN, everywhere, this:

std::ifstream file("filename.txt", ios::in, filebuf::sh_read);

BUT, sh_read isn't a member of std::filebuf and I don't have just filebuf::sh_read because I'm using the new header, i.e. <fstream> instead of <fstream.h>. Including <fstream.h> as well allows me to use sh_read but then there are "no constructors that take 3 arguments" Is shared access even supported anymore, or was it supported to begin with?? And do I have to convert all my code to using Windows API files?

Originally posted by Hunter2
My problem is that I want to open a file with read and write sharing, using a std::ifstream, but I can't.

Is this what you want?

Code:

  char buf[100];
  fstream f("myfile.txt", ios::in | ios::out);
  
  f << "testing";
  f.seekg(0);
  f >> buf;
  cout <<buf <<endl;

It's very interesting, but unfortunately, no What I mean is, open it in this way:

Code:

std::ifstream file("theFile.txt"/*other parameters*/);
//do some stuff, but don't close file
std::ifstream file2("theFile.txt"/*other parameters*/);

Or something along those lines, so that the second file opens properly as well. With WinAPI you would open it with FILE_SHARE_READ, right? I'm looking for an equivalent with ifstream, or fstream, whichever it works for. Or do I have it all wrong?

Well, to start with ifstream is for read only files, afaik. ostream is for writing, fstream can be used for either.

As for opening the same file twice, I haven't tried, but I guess if you careful with the buffer flushing you should be OK, but I wouldn't guarantee it.

Odd, I thought the second open failed when I tried. Maybe I got something wrong, I guess I'll have to do more testing.

**Deleted post's previous contents**

Heh... oops.. I didn't allow file sharing with the WinAPI calls. I'm all better now