Coloured Error Messages for Console Applications

Introduction

While working with console applications, sometimes we want to print coloured error messages. Here is the implementation of a very small function which will help in accomplishing the task.

int _teprintf(TCHAR *format, ...) 
{
    HANDLE hStdOut = NULL ;
    TCHAR szBuffer[1024] ;
    va_list arg_list ;
    int nBuf = 0 ;
    va_start(arg_list,format);
    nBuf = _vsntprintf(szBuffer,1024,format,arg_list) ;
    va_end(arg_list) ;
    //get console output handle
    hStdout = GetStdHandle(STD_OUTPUT_HANDLE);    
    if(!hStdout) {
        return 0;
    }
    //set red colour
    if (! SetConsoleTextAttribute(hStdout, FOREGROUND_RED | 
        FOREGROUND_INTENSITY)) {
        return 0;
    }
    //print 
    nBuf = _tprintf(_T("%s"),szBuffer) ;
    //restore to white.
    if (! SetConsoleTextAttribute(hStdout, FOREGROUND_RED |
        FOREGROUND_BLUE | 
        FOREGROUND_GREEN)) {
        return 0;
    }
    return nBuf ;
}

You can use it as follows:

int _tmain(int argc, _TCHAR* argv[])
{
	_teprintf(_T("\nI am Error\n")) ;
	_tprintf(_T("\nI am Normal\n")) ;
	return 0;
}

Though this is trivial, it is fun..!

History

5^th December, 2006: Initial post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Prateek Kumar Dubey

Other
Microsoft

India

Member

I am currently working with Microsoft at Bangalore (India). My interest lies in areas of generic C++ and windows development. Apart from office hours I try to develop new and useful small tools.
Well, I still feel that I need to be more serious..!
Smile | :)

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more perfect idea

Yacha

20:52 13 Dec '06

We can use IOStreams to solve this task more perfect.



main.cpp

...

console::console_buffer out_buf(console::console_buffer::output);

std::basic_streambuf* prev_out_buf = std::wcout.rdbuf(&out_buf);

...

console::color green_color(color::foreground::value | color::foreground::value);

std::cout << green_color << "TEKISUTO WA MIDORIIRO DESU" << console::def_color << std::endl;

....

color.hpp

...

class color

{

public:

	enum colour

	{

          blue = FOREGROUND_BLUE,

	  green = FOREGROUND_GREEN,

	  red = FOREGROUND_RED,

	  intensity = FOREGROUND_INTENSITY

	};

	template struct foreground { enum { value = c }; };

	template struct background { enum { value = c << 4 }; };

	explicit color(short c)

		: c_(c)

	{

	}

	color()

		: c_(foreground::value | foreground::value | foreground::value)

	{

	}

	short get() const { return c_; }

	//! set a new color

	template

	friend std::basic_ostream& operator << (std::basic_ostream& os, color const& c);

private:

	short c_;

};

template

inline std::basic_ostream& operator << (std::basic_ostream& os, color const& c)

{

	if(os.good())

	{

		//! get current stream buffer

		if(console_buffer* screen = dynamic_cast* >(os.rdbuf()))

		{

			os.flush();

			static_cast(screen->set_color(c));

		}

	}

	return os;

}

...

console_buffer.hpp

...

template >

class console_buffer

		: public std::basic_filebuf

{

public:

	//! available console type

	enum console_type

	{

		devnul	= 0,

		output	= STD_OUTPUT_HANDLE,

		input	= STD_INPUT_HANDLE,

		error	= STD_ERROR_HANDLE

	};

	explicit console_buffer(console_type con_type)

		: con_type_(con_type)

		, console_(0)

	{

		HANDLE h = ::GetStdHandle(con_type);

		//! ran under service or /dev/nul

		if(con_type == devnul || h == 0)

		{

			h = ::CreateFileW(L"NUL", GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, 0);

			con_type = devnul;

		}

		if(INVALID_HANDLE_VALUE == h)

			throw std::runtime_error("invalid handle value");

		//! if not /dev/nul, should duplicate handle

		if(con_type != devnul)

		{

			HANDLE dup(0);

			HANDLE process(GetCurrentProcess());

			if(!::DuplicateHandle(process, h, process, &dup, 0, 0, DUPLICATE_SAME_ACCESS))

				throw std::runtime_error("duplicate error");

			h = dup;

		}

		//! opend file descriptor

		int handle = ::_open_osfhandle(reinterpret_cast<::intptr_t>(h), _O_TEXT);

		//! open C file stream

		console_ = ::_fdopen(handle, "a");

		//! initialize basic_filebuf

		std::basic_filebuf::_Init(console_, std::basic_filebuf::_Newfl);

		default_color_ = this->do_get_default_color();

	}

	//! return default screen buffer color

	color default_color() const { return default_color_; }

	//! set new screen buffer color

	color set_color(color const& _new_color)

	{

		HANDLE h = this->get_console_handle();

		if(INVALID_HANDLE_VALUE  != h)

		{

			::CONSOLE_SCREEN_BUFFER_INFO info = { sizeof(CONSOLE_SCREEN_BUFFER_INFO), 0 };

			if(::GetConsoleScreenBufferInfo(h, &info))

			{

				color prev(info.wAttributes & 0x00ff);

				::SetConsoleTextAttribute(h, (info.wAttributes & 0xff00) | _new_color.get());

				return prev;

			}

		}

		return color();

	}

	...

 

private:

	color do_get_default_color() const

	{

		HANDLE h = this->get_console_handle();

		if(INVALID_HANDLE_VALUE  != h)

		{

			::CONSOLE_SCREEN_BUFFER_INFO info = { sizeof(CONSOLE_SCREEN_BUFFER_INFO), 0 };

			if(::GetConsoleScreenBufferInfo(h, &info))

				return color(info.wAttributes & 0x00ff);

		}

		return color();

	}

	//! return current console handle

	HANDLE get_console_handle() const

	{

		HANDLE h = INVALID_HANDLE_VALUE;

		int fd = ::_fileno(console_);

		if(fd != -1)

			h = reinterpret_cast(::_get_osfhandle(fd));

		return h;

	}

private:

	console_type con_type_;//! console type

	::FILE*      console_; //! C file stream

	color        default_color_;//! defaulr console color

};

...

template

inline std::basic_ostream& def_color(std::basic_ostream& os)

{

	if(os.good())

	{

		//! //! get current stream buffer

		if(console_buffer* screen = dynamic_cast* >(os.rdbuf()))

		{

			os.flush();

			static_cast(screen->set_color(screen->default_color()));

		}

	}

	return os;

}

restore original colors

osy

23:03 5 Dec '06

nice idea! If a user selected non standard colors you can restore this with the following lines: `// save current text colors CONSOLE_SCREEN_BUFFER_INFO csbiInfo; ::GetConsoleScreenBufferInfo( consoleOut_, &csbiInfo ); // ...write message // reset colors ::SetConsoleTextAttribute( consoleOut_, csbiInfo.wAttributes );`
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