Thread: redirecting a file stream to stdout

Just print to std::cout?

stream iterators might be a good choice

yes that is true but then i need at print line make that distinction :

Code:

if(/*file*/)
  fs.open();

// and then 


if(/*file*/)
  fs << "    foo\n";
else
  cout<< "  foo\n";

// then again somewhere in the code 


if(/*file*/)
  fs << "    bar\n";
else
  cout<< "  bar\n";

but what i used to do is to define my fp in the beginning and then just print, without checking the file existence every time, like this

Code:

if(/*file exists*/)
     fd = open();
else
    fd = 0;

Is this more clear?? Is it a good practice ???

Originally Posted by baxy

yes that is true but then i need at print line make that distinction

No, you don't. Write functions that operate on std::ostream. Then, you can pass std::cout, or some other output stream, by reference to the function that calls the others.

Or just create a reference to the stream you are going to use and send all output to this reference

Code:

#include <iostream>
#include <fstream>

int main()
{
    std::ofstream file("test.txt");

    std::ostream& used_stream = file;

    used_stream << "Test\n";

    std::ostream& used_stream2 = std::cout;

    used_stream2 << "Test\n";

    return 0;

}

Originally Posted by baxy

yes, but then again when call the function you need to make this distinction

No you don't

Code:

#include <iostream>
#include <fstream>
#include <string>

static void writeLine(std::ostream& ostream, std::string var);
int main()
{
    writeLine(std::cout, "Test\n");

    std::ofstream file("test.txt");

    writeLine(file, "Test\n");
}

static void writeLine(std::ostream& ostream, std::string var)
{
    ostream << var;
}

Originally Posted by baxy

yes, but then again when call the function you need to make this distinction ... right or am i misunderstanding something ?

Yes, but that is only at one place.

Maybe you could do something like this:

Code:

#include <iostream>
#include <string>
#include <fstream>

void write(std::ostream& os, const std::string& s)
{
    os << s << '\n';
}

int main(int argc, char **argv)
{
    if (argc != 2) {
        std::cerr << "Usage: " << argv[0] << " -c | filename\n";
        return 1;
    }

    std::ofstream ofs;
    std::ostream& os = std::string(argv[1]) == "-c"
                     ? std::cout
                     : (ofs.open(argv[1]), ofs);

    write(os, "hello");

    return 0;
}

Heh, that's like a combination of my suggestion with vart's suggestion.

Originally Posted by laserlight

Heh, that's like a combination of my suggestion with vart's suggestion.

Exactly! That's what I did all right.