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

From:

Kira Yamato <kirakun@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Fri, 5 Oct 2007 15:13:05 -0400

Message-ID:

<2007100515130575249-kirakun@earthlinknet>

On 2007-10-05 12:59:39 -0400, Adrian <nntp@bluedreamer.com> said:

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;
}

I tried to implement a STL solution below, but it won't compile:

#include <iostream>
#include <fstream>
#include <iterator>
#include <algorithm>

using namespace std;

int main(int argc, char **argv)
{
    copy(istream_iterator<char>(argc >= 2 ? ifstream(argv[1]) : cin),
// this line won't compile!
        istream_iterator<char>(),
        ostream_iterator<char>(cout));

  return 0;
}

Does anyone know why?

--

-kira