Re: cout vs. ofstream output
<roger.a.banks@gmail.com> wrote:
I've written a little command line utility. So far it just reads from
stdin using cin and outputs to stdout using cout. I would like to
generalize it some by being able to specify input and output files on
the command line while retaining the ability to use stdin and stdout
if no files are specified on the command line. My thinking is that I
need to replace all instances of cin and cout with some generic names
like 'infile' and 'outfile' and then set them to point to either (cin
| cout) or the file specified on the command line after parsing the
command line, but I can't seem to find the correct way to code this.
Is this the correct approach and, if so, could someone post a hint and/
or sample code? Thanks!
Sure. Here is some example code showing how such a infile could be coded:
int main(int argc, char** argv)
{
bool usecin;
std::string infilename;
// fill in those variables
std::ifstream ifs;
if (!usecin) ifs.open(infilename.c_str());
std::istream& infile = (usecin)?(std::cin):ifs;
//later:
int i;
infile >> i;
return i;
}
I'm sure you can figure out how to add the outfile variable to the above.
Notice the fact that infile is a reference. That is the easiest way to just
make this work.
Unfortunately, this particular solution form could be problematic if
additional user-defined functions are used, as that would nesesiatate
additional parameters to the functions. (namely a "std::istream& infile"
parameter and a "std::ostream& outfile" parameter. )
I've seen solution that involved replacing the streambuf of std::cin and
std::cout, but those don't seem very clean to me.