Re: Whats the C++ equivalent of reading from stdin or a file

From:

red floyd <no.spam@here.dude>

Newsgroups:

comp.lang.c++

Date:

Fri, 05 Oct 2007 17:23:30 GMT

Message-ID:

<mquNi.55664$Um6.42702@newssvr12.news.prodigy.net>

Adrian wrote:

What is the best was to do this in c++. This is going to be used for
unix util that should be able to have input piped to it or file name
spec

#include <stdio.h>

int main(int argc, char *argv[])
{
   FILE *fp;
   int c;
   if(argc==2)
   {
      fp=fopen(argv[1], "r");
   }
   else
   {
      fp=stdin;
   }

   while((c=fgetc(fp))!=EOF)
   {
      printf("%c",c);
   }
   return 0;
}

I assume it has something to do with the underlying buffer and have
tried this but it wont compile.
#include <iostream>
#include <fstream>

int main(int argc, char *argv[])
{
   std::ifstream in;

   if(argc==2)
   {
      in.open(argv[0]);
   }
   else
   {
      in.rdbuf(std::cin.rdbuf());
   }

   int c;
   while(c==in.get())
   {
      std::cout << c;
   }

   return 0;
}

maybe something like:

int main()
{

    std::ifstream in;
         std::istream* in_p = &std::cin;

         if (argc == 2)
         {
            in.open(argv[1]);
            if (in.good())
               in_p = &in;
            else
               in.close();
         }

         std::istream& is = *in_p;

         // yada yada yada
}

}