Redirecting function output to /dev/null

Question

I am using a library that is printing a warning message to cout or cerr. I don\'t want this warning message to reach the output of my program. How

Answer 1

May I suggest a hack? Set a bad/fail bit on the relevant stream before use of a library function.

#include <iostream>

void foo()
{
    std::cout << "Boring message. " << std::endl;
}

int main()
{
    std::cout.setstate(std::ios::failbit) ;
    foo();
    std::cout.clear() ;
    std::cout << "Interesting message." << std::endl;
    return 0;
}

Answer 2

If you are sure that thing does not redirect output (e.g. to /dev/tty/, which would be standard-out again) (which I don't think), you could redirect before calling them.

#include <iostream>
#include <sstream>

void foobar() { std::cout << "foobar!\nfrob!!"; }

int main () {    
    using namespace std;

    streambuf *old = cout.rdbuf(); // <-- save        
    stringstream ss;

    cout.rdbuf (ss.rdbuf());       // <-- redirect
    foobar();                      // <-- call
    cout.rdbuf (old);              // <-- restore

    // test
    cout << "[[" << ss.str() << "]]" << endl;
}

Answer 3

Use ios::rdbuf:

#include <iostream>

void foo()
{
    std::cout << "Boring message. " << std::endl;
}

int main()
{
    ofstream file("/dev/null");

    //save cout stream buffer
    streambuf* strm_buffer = cout.rdbuf();

    // redirect cout to /dev/null
    cout.rdbuf(file.rdbuf());

    foo();

    // restore cout stream buffer
    cout.rdbuf (strm_buffer);

    std::cout << "Interesting message." << std::endl;
    return 0;
}