?
Solved

Basic Question: Outputting to streams

Posted on 2004-10-13
3
Medium Priority
?
211 Views
Last Modified: 2010-04-01
Hello, I'm writing a tiny Console App which can either output to screen or a file. I'm new to C/C++ although I'm fairly good at HTML/PHP/VB/etc.. so I understand programming concepts, just not anything to do with C


At the minute I'm having to use:

if(fileoutput==0) {
      printf("%c", letter);
} else {
      fputc(letter, outstream);
}

Is ther a nice way to check a cariable and use ONE command to ouypuy the desired character? letter is, in this case a char and outstream is a file (IF using file output, otherwise it's unset) (This probably obvious to everyone, but...)

How can I make this nicer?
0
Comment
Question by:basiclife
3 Comments
 
LVL 17

Accepted Solution

by:
rstaveley earned 1000 total points
ID: 12298038
Here's how to do it in C:

--------8<--------
#include <stdio.h>

FILE *whatever = stdout;

void display_char(char c)
{
      fputc(c,whatever);
}

int main()
{
FILE *fout;
const char msg[] = "Hello, world\n",*str;

      fout = fopen("x.txt","w");

      whatever = stdout;
      for (str = msg;*str;++str)
            display_char(*str);

      whatever = fout;
      for (str = msg;*str;++str)
            display_char(*str);

      whatever = stderr;
      for (str = msg;*str;++str)
            display_char(*str);

      fclose(fout);
}
--------8<--------
0
 
LVL 39

Expert Comment

by:itsmeandnobodyelse
ID: 12298821
Or C++:

#include <iostream>
#include <fstream>
using namespace std;

void main(int nArgs, char* pszArgs[])
{
   ofstream ofs;
   ostream  couts = cout;   // save old cout
   if (nArgs > 1)
   {
       ofs.open(pszArgs[1]);
       if (ofs)
           cout = ofs;
   }  
   cout << "Any you want " << endl;

   if (nArgs > 1)
   {
        ofs.close();
        cout = couts; // get saved back
   }
}

Regards, Alex



0
 
LVL 15

Expert Comment

by:efn
ID: 12304637
Assigning and copying stream objects may work, but may not be portable.  It's safer to fiddle with the stream buffer, as described in:

http://www.icce.rug.nl/documents/cplusplus/cplusplus05.html#l91

Other references:

http://www.langer.camelot.de/Articles/Papers/IOStreams/IOStreams.htm

http://www.roguewave.com/support/docs/sourcepro/stdlibug/34-2.html
0

Featured Post

[Webinar] Kill tickets & tabs using PowerShell

Are you tired of cycling through the same browser tabs everyday to close the same repetitive tickets? In this webinar JumpCloud will show how you can leverage RESTful APIs to build your own PowerShell modules to kill tickets & tabs using the PowerShell command Invoke-RestMethod.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Often, when implementing a feature, you won't know how certain events should be handled at the point where they occur and you'd rather defer to the user of your function or class. For example, a XML parser will extract a tag from the source code, wh…
What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

593 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question