CODEWITHSUNDEEP
c++consolestdoutcout
Jason Swager
Jason Swager

Reputation: 6501

Custom C++ cout class - output to both console and log file

I'm working on a program that makes heavy use of "cout << strSomething;" to log information to the console. I need to modify the program so that all console output goes to both the console AND a file. Although I can modify the "cout <<" in our code, there are several large third party libraries that also use "cout <<"; those libraries cannot be modified due to their licenses - so modifying all references to "cout <<" is not a solution. Also, the use of "wtee.exe" isn't possible due to the manner in which the command lines are executed.

I am using Visual Studio 2008. I've seen the posting at Google Groups: redirect cout to file, which appears to do EXACTLY what I want to do. The only problem is that the code won't compile. I get C2248 errors "cannot access protected member" on the ->overflow() and ->sync() method calls.

Would anyone know how to get this code to compile? Or an alternate way of redirecting cout to both console and file simultaneously?

Upvotes: 9

Views: 11585

Answers (7)

Jim Thomas
Jim Thomas

Reputation: 31

This easily extends to additional streams.

OstreamFork.hpp -- Distribute data to 2 streams simultaneously

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

class ostreamFork           // Write same data to two ostreams
{
public:
  ostream& os1 ;
  ostream& os2 ;

  ostreamFork( ostream& os_one , ostream& os_two )
  : os1( os_one ) ,
    os2( os_two )
  {}

 } ;

                          // For data: int, long , ...
 template <class Data>
 ostreamFork& operator<<( ostreamFork& osf , Data d )
 {
   osf.os1 << d ; 
   osf.os2 << d ;
   return osf ;
 }
                        // For manipulators: endl, flush
 ostreamFork& operator<<( ostreamFork& osf , ostream& (*f)(ostream&)  )
 {
   osf.os1 << f ; 
   osf.os2 << f ;
   return osf ;
 }

                            // For setw() , ...
template<class ManipData>
 ostreamFork& operator<<( ostreamFork& osf , ostream& (*f)(ostream&, ManipData )  )
 {
   osf.os1 << f ; 
   osf.os2 << f ;
   return osf ;
 }

TestOstreamFork.cpp: 

#include "stdafx.h"
#include <fstream>
  using namespace std ;
#include "ostreamFork.hpp"

int main(int argc, char* argv[])
{
  ofstream file( "test2.txt" ) ;
  ostreamFork osf( file , cout ) ;

  for ( int i = 0 ; i < 10 ; i++ )
  {
    osf << i << setw(10) << " " << 10*i << endl  ;
  }

    return 0 ;
}

Output to both cout and test2.txt:

0          0
1          10
2          20
3          30
4          40
5          50
6          60
7          70
8          80
9          90

Upvotes: 3

Andr&#233; Aichert
Andr&#233; Aichert

Reputation: 322

Sorry to warm this up so late, but this here should be a solution with redirection of cout to a teebuffer based on Dietmar Kühl's solution on Google groups.

Usage is simply

GetSetLog log("myfile.log");

During the lifetime of the object "log" everything will be written to both cout/cerr and file

https://sourceforge.net/p/getset/code/ci/master/tree/GetSet/GetSetLog.hxx

Upvotes: 0

Ali1S232
Ali1S232

Reputation: 3411

you can just use a wrapper class to do so, somthing like this

#include <iostream>
#include <fstream>

...

class streamoutput
{
    std::ofstream fileoutput;
    public:
    streamoutput(char*filename){
        fileoutput.open(filename);
    }
    ~streamoutput(){
        fileoutput.close();
    }
    template<class TOut> streamoutput& operator <<(const TOut& data)
    {
        fileoutput << data;
        std::cout << data;
        return this;
    }
};

extern streamoutput cout("logfile.log");

declare cout like that and just change all your #include <iostream> to include this wrapper (remeber cout is external variable so you have to declere it in one of your source codes too).

Upvotes: 0

A. K.
A. K.

Reputation: 38264

What you can do is capture the std::cout.rdbuf() with a pointer to std::streambuf, then i think you should be able to write all the outputs to std::cout to some file.

Upvotes: 1

Troubadour
Troubadour

Reputation: 13431

The sync calls can be replaced with pubsync. As for the overflow call I think that may be a typo. as it looks as if it should be a call to sputc.

Upvotes: 1

Sam Miller
Sam Miller

Reputation: 24174

The boost::iostreams::tee_device is made for this

#include <boost/iostreams/stream.hpp>
#include <boost/iostreams/tee.hpp>

#include <fstream>
#include <iostream>

int
main()
{
    typedef boost::iostreams::tee_device<std::ostream, std::ofstream> Tee;
    typedef boost::iostreams::stream<Tee> TeeStream;

    std::ofstream file( "foo.out" );
    Tee tee( std::cout, file );

    TeeStream both( tee );

    both << "this goes to both std::cout and foo.out" << std::endl;

    return 0;
}

sample invocation:

samm$ ./a.out
this goes to both std::cout and foo.out
samm$ cat foo.out
this goes to both std::cout and foo.out
samm$

Upvotes: 12

flownt
flownt

Reputation: 760

if you're desperate: 

#define protected public
#include <iostream>
#undef protected

this is a gross hack, but it usually works.

Upvotes: 2

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