Number of open file in a C++ program

Question

Is there a simple way to get the number of files opened by a c++ program.

I would like to do it from my code, ideally in C++.

I found this blog article which is using a loop through all the available file descriptor and testing the result of fstat but I am wondering if there is any simpler way to do that.

Edit

It seems that there are no other solution than keeping a count of the files opened. Thanks to everybody for your help.

Kevin

Answer 1

Since the files are FILE *, we could do something like this:

In a headerfile that gets included everywhere:

#define fopen(x, y) debug_fopen(x, y, __FILE__, __LINE__)
#define fclose(x)   debug_fclose(x)

in "debugfile.cpp" (must obviously NOT use the above #define's)

struct FileInfo
{
   FileInfo(const char *nm, const char fl, int ln) :  
      name(nm), file(fl), line(ln) {}

   std::string name;
   const char *file;
   int line;
};

std::map<FILE*, FileInfo> filemap;

FILE *debug_fopen(const char *fname, const char *mode, const char *file, int line)
{
   FILE *f = fopen(fname, mode);
   if (f)
   {
      FileInfo inf(fname, file, line);
      filemap[f] = inf;
   }
}

int debug_fclose(FILE *f)
{
   int res = fclose(f);
   filemap.erase(f);
   return res;
}

// Called at some points. 
void debug_list_openfiles()
{
   for( i : filemap )
   {
       cerr << "File" << (void *) i.first << " opened as " << i.second.name 
            << " at " <<  i.second.file << ":" << i.second.line << endl;
   }
}

(I haven't compiled this code, and it's meant to show the concept, it may have minor bugs, but I think the concept would hold - as long as your code, and not some third party library is leaking)