How to update (refresh) console screen? - c

Question

I'm writing a program that shows some information on screen and I want them to be updated each second.
What should I do?
I'm writing a C console application on Windows.

Answer 1

The Pianist, you can work with a console using WinAPI functions.
HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
if (!hConsole)
return;
After that determine the cursor position:
CONSOLE_SCREEN_BUFFER_INFO csbi = {0};
GetConsoleScreenBufferInfo(hConsole, &csbi);
COORD coordCur = csbi.dwCursorPosition;
And...
while (TRUE) { // your cycle goes here
// ...
// now you can change position of the cursor
coordCur.X = newX;
coordCur.Y = newY;
SetConsoleCursorPosition(hConsole, coordCur);
// and print any information from the new position
printf("..."); // old text will be replaced
}
So you don't need to clear and refresh all console if you want to change a small piece of text.
ps. Don't forget to release a handle:
CloseHandle(hConsole);

Answer 2

There's a KB article on that topic.
Two options:
Write a function that will programmatically clear the screen
/* Standard error macro for reporting API errors */
#define PERR(bSuccess, api){if(!(bSuccess)) printf("%s:Error %d from %s \
on line %d\n", __FILE__, GetLastError(), api, __LINE__);}
void cls( HANDLE hConsole )
{
COORD coordScreen = { 0, 0 }; /* here's where we'll home the
cursor */
BOOL bSuccess;
DWORD cCharsWritten;
CONSOLE_SCREEN_BUFFER_INFO csbi; /* to get buffer info */
DWORD dwConSize; /* number of character cells in
the current buffer */
/* get the number of character cells in the current buffer */
bSuccess = GetConsoleScreenBufferInfo( hConsole, &csbi );
PERR( bSuccess, "GetConsoleScreenBufferInfo" );
dwConSize = csbi.dwSize.X * csbi.dwSize.Y;
/* fill the entire screen with blanks */
bSuccess = FillConsoleOutputCharacter( hConsole, (TCHAR) ' ',
dwConSize, coordScreen, &cCharsWritten );
PERR( bSuccess, "FillConsoleOutputCharacter" );
/* get the current text attribute */
bSuccess = GetConsoleScreenBufferInfo( hConsole, &csbi );
PERR( bSuccess, "ConsoleScreenBufferInfo" );
/* now set the buffer's attributes accordingly */
bSuccess = FillConsoleOutputAttribute( hConsole, csbi.wAttributes,
dwConSize, coordScreen, &cCharsWritten );
PERR( bSuccess, "FillConsoleOutputAttribute" );
/* put the cursor at (0, 0) */
bSuccess = SetConsoleCursorPosition( hConsole, coordScreen );
PERR( bSuccess, "SetConsoleCursorPosition" );
return;
}
Use a system function (not very pretty; requires starting a shell and a command)
system("cls");

Answer 3

Since you are on Windows, you can do this:
system('cls')
Here is an example:
#include <stdio.h>
int main()
{
printf("Press enter to clear the screen.");
getchar();
system("cls");
return 0;
}
If you are developing using Microsoft Visual Studoo and you want to programmatically clear the screen by outputting spaces, see Example 2 at http://msdn.microsoft.com/en-us/library/windows/desktop/ms682022(v=vs.85).aspx.

Answer 4

If you had searched google before asking, you would have found this link right in the first results.
To quote one of the methods:
Windows:
#include <windows.h>
void ClearScreen()
{
HANDLE hStdOut;
CONSOLE_SCREEN_BUFFER_INFO csbi;
DWORD count;
DWORD cellCount;
COORD homeCoords = { 0, 0 };
hStdOut = GetStdHandle( STD_OUTPUT_HANDLE );
if (hStdOut == INVALID_HANDLE_VALUE) return;
/* Get the number of cells in the current buffer */
if (!GetConsoleScreenBufferInfo( hStdOut, &csbi )) return;
cellCount = csbi.dwSize.X *csbi.dwSize.Y;
/* Fill the entire buffer with spaces */
if (!FillConsoleOutputCharacter(
hStdOut,
(TCHAR) ' ',
cellCount,
homeCoords,
&count
)) return;
/* Fill the entire buffer with the current colors and attributes */
if (!FillConsoleOutputAttribute(
hStdOut,
csbi.wAttributes,
cellCount,
homeCoords,
&count
)) return;
/* Move the cursor home */
SetConsoleCursorPosition( hStdOut, homeCoords );
}