Output string to both console and file at the same time

This is a discussion on Output string to both console and file at the same time within the C++ Programming forums, part of the General Programming Boards category; Hi guys, I'm new to c++, I'm trying to print a string to both console and a file at the ...

  1. #1
    Registered User
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    Output string to both console and file at the same time

    Hi guys,

    I'm new to c++, I'm trying to print a string to both console and a file at the same time.

    I know this works:

    Code:
    //This is just an example
    cout<<"I want to print "<<3+4<<" in to a file."<<endl;
    ofstream out("file.txt");
    out<<"I want to print "<<3+4<<" in to a file."<<endl;
    but is there a better way to do it without repeat the code? Because the actual stuff I'm going to print is more complicated than the example above.

    thanks!

  2. #2
    Banned master5001's Avatar
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    Actually, if it were me, I would put everything into a stringstream, and output the stringstream to both the file and standard out.

  3. #3
    Use this: dudeomanodude's Avatar
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    overload ostream
    Ubuntu Desktop
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  4. #4
    Registered User Codeplug's Avatar
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    Create your own streambuf that outputs to two internal streambufs...
    Code:
    #include <iostream>
    #include <fstream>
    #include <streambuf>
    
    //------------------------------------------------------------------------------
    
    template <class charT, class traits = std::char_traits<charT> >
    class basic_teebuf : public std::basic_streambuf<charT, traits>
    {
    public:
        typedef charT char_type;
        typedef typename traits::int_type int_type;
        typedef typename traits::pos_type pos_type;
        typedef typename traits::off_type off_type;
        typedef traits traits_type;
        typedef std::basic_streambuf<charT, traits> streambuf_type;
    
    private:
        streambuf_type *m_sbuf1;
        streambuf_type *m_sbuf2;
        char_type *m_buffer;
    
        enum {BUFFER_SIZE = 4096 / sizeof(char_type)};
    
    public:
        basic_teebuf(streambuf_type *sbuf1, streambuf_type *sbuf2)
            : m_sbuf1(sbuf1), m_sbuf2(sbuf2), m_buffer(new char_type[BUFFER_SIZE])
        {
            setp(m_buffer, m_buffer + BUFFER_SIZE);
        }//constructor
    
        ~basic_teebuf()
        {
            pubsync();
            delete[] m_buffer;
        }//destructor
    
    protected:
        virtual int_type overflow(int_type c = traits_type::eof())
        {
            // empty our buffer into m_sbuf1 and m_sbuf2
            std::streamsize n = static_cast<std::streamsize>(pptr() - pbase());
            std::streamsize size1 = m_sbuf1->sputn(pbase(), n);
            std::streamsize size2 = m_sbuf2->sputn(pbase(), n);
            if (size1 != n || size2 != n)
                return traits_type::eof();
    
            // reset our buffer
            setp(m_buffer, m_buffer + BUFFER_SIZE);
    
            // write the passed character if necessary
            if (!traits_type::eq_int_type(c, traits_type::eof()))
            {
                traits_type::assign(*pptr(), traits_type::to_char_type(c));
                pbump(1);
            }//if
    
            return traits_type::not_eof(c);
        }//overflow
    
        virtual int sync()
        {
            // flush our buffer into m_sbuf1 and m_sbuf2
            int_type c = overflow(traits_type::eof());
    
            // checking return for eof.
            if (traits_type::eq_int_type(c, traits_type::eof()))
                return -1;
    
            // flush m_sbuf1 and m_sbuf2
            if (m_sbuf1->pubsync() == -1 || m_sbuf2->pubsync() == -1)
                return -1;
    
            return 0;
        }//sync
    };//basic_teebuf
    
    typedef basic_teebuf<char>    teebuf;
    typedef basic_teebuf<wchar_t> wteebuf;
    
    //------------------------------------------------------------------------------
    
    template <class charT, class traits = std::char_traits<charT> >
    struct scoped_basic_streambuf_assignment
    {
        typedef std::basic_ostream<charT, traits> ostream_type;
        typedef std::basic_streambuf<charT, traits> streambuf_type;
    
        ostream_type &m_s;
        streambuf_type *m_orig_sb;
    
        scoped_basic_streambuf_assignment(ostream_type &s, streambuf_type *new_sb) 
            : m_s(s)
        {
            m_orig_sb = m_s.rdbuf(new_sb);
        }//constructor
    
        ~scoped_basic_streambuf_assignment()
        {
            m_s.rdbuf(m_orig_sb);
        }//destructor
    };//scoped_basic_streambuf_replacement
    
    typedef scoped_basic_streambuf_assignment<char>    scoped_streambuf_assignment;
    typedef scoped_basic_streambuf_assignment<wchar_t> scoped_wstreambuf_assignment;
    
    //------------------------------------------------------------------------------
    
    using namespace std;
    
    int main()
    {
        ofstream file("data.txt");
    
        // tbuf will write to both file and cout
        teebuf tbuf(file.rdbuf(), cout.rdbuf());
    
        // replace cout's streambuf with tbuf
        scoped_streambuf_assignment ssa(cout, &tbuf);
    
        cout << "Hello World" << endl;
    
        return 0;
    }//main
    gg

  5. #5
    Super Moderator VirtualAce's Avatar
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    Actually, if it were me, I would put everything into a stringstream, and output the stringstream to both the file and standard out.
    My exact solution for a similar problem I had a couple of weeks ago. Worked like a charm.

  6. #6
    Nor
    Nor is offline
    h ֆhr s Nor's Avatar
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    Codeplug code is a little complex. you said your new so try this
    Code:
    #include <iostream> //console commands
    #include <fstream>  // file commands
    //Global stuff - bad way to do this<<
    std::fstream file;
    void output(char* string);
    int main(void){
        char TEXT[] = "some debuging stuff to look at\n Nor is Great."
        file.open("testfile", std::ios::out);
        if( !file.is_open()) // please note the '!'. it is very inportant to check for errors.
            exit(1);            //could not open file
        output(&TEXT[0])l
        file.close();
        return 0;
    }   
    void output(char* string){
     std::cout << string << std::endl;
     file << string << std::endl;
    //or file.write(string, strlen(string));
    }
    Try to help all less knowledgeable than yourself, within
    the limits provided by time, complexity and tolerance.
    - Nor

  7. #7
    Cat without Hat CornedBee's Avatar
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    8,893
    Code:
    ./myprogram | tee outfile.txt
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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