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How do I clear the console in BOTH Windows and Linux using C++

Posted by: admin November 29, 2017 Leave a comment

Questions:

I need a cross platform solution for clearing the console in both Linux and Windows written in C++. Are there any functions in doing this? Also make note that I don’t want the end-user programmer to have to change any code in my program to get it to clear for Windows vs Linux (for example if it has to pick between two functions then the decision has to be made at run-time or at compile-time autonomously).

Answers:

Short answer: you can’t.

Longer answer: Use a curses library (ncurses on Unix, pdcurses on Windows). NCurses should be available through your package manager, and both ncurses and pdcurses have the exact same interface (pdcurses can also create windows independently from the console that behave like console windows).

Most difficult answer: Use #ifdef _WIN32 and stuff like that to make your code act differently on different operating systems.

Questions:
Answers:

There is no generic command to clear the console on both platforms.

#include <cstdlib>

void clear_screen()
{
#ifdef WINDOWS
    std::system("cls");
#else
    // Assume POSIX
    std::system ("clear");
#endif
}

Questions:
Answers:

On linux it’s possible to clear the console. The finest way is to write the following escape sequence to stdout:

write(1,"\E[H\E[2J",7);

which is what /usr/bin/clear does, without the overhead of creating another process.

Questions:
Answers:

A simple trick: Why not checking the OS type by using macros in combination with using the system() command for clearing the console?
This way, you are going to execute a system command with the appropriate console command as parameter.

#ifdef _WIN32
#define CLEAR "cls"
#else //In any other OS
#define CLEAR "clear"
#endif

//And in the point you want to clear the screen:
//....
system(CLEAR);
//....

Questions:
Answers:

The question as posted is unanswerable, because it imposes impossible restrictions. “Clearing the screen” is a very different action across different operating systems, and how one does it is operating system specific. See this Frequently Given Answer for a full explanation of how to do it on several popular platforms with “consoles” and platforms with “terminals”. You’ll also find in the same place some explanation of the common mistakes to avoid, several of which are — alas! — given above as answers.

Questions:
Answers:

This is how you do it on any other platform but it doesn’t work in Windows:

cout << "\f";

Perhaps you’ll need to make a conditional compilation:

void clrscr()
{
#ifdef _WIN32
    HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
    COORD coord = {0, 0};
    DWORD count;
    CONSOLE_SCREEN_BUFFER_INFO csbi;
    GetConsoleScreenBufferInfo(hStdOut, &csbi);
    FillConsoleOutputCharacter(hStdOut, ' ',
                               csbi.dwSize.X * csbi.dwSize.Y,
                               coord, &count);
    SetConsoleCursorPosition(hStdOut, coord);
#else
    cout << "\f";
#endif
}

Questions:
Answers:

I know this isn’t answering my own question but!
This works for Windows (#include <windows.h>):

void clrscr()
{
    HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
    COORD coord = {0, 0};
    DWORD count;

    CONSOLE_SCREEN_BUFFER_INFO csbi;
    GetConsoleScreenBufferInfo(hStdOut, &csbi);

    FillConsoleOutputCharacter(hStdOut, ' ', csbi.dwSize.X * csbi.dwSize.Y, coord, &count);

    SetConsoleCursorPosition(hStdOut, coord);
}

Questions:
Answers:

Well there is a very close alternative to clearing the screen. You could try using a for loop that repeats new lines a lot. For example:

for (i = 0; i < 100000; i++)
{
  printf ("\n\n\n\n\n");
}

After you do this loop the terminal wan’t allow you to scroll back to where you were at the top, an unprofessional approach with common sense pretty much. It does not directly answer what you are asking but it can work.

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Answers:

Short answer

void cls(void)
{
    system("cls||clear");
    return;
}

Long answer, please read:

system("pause") clarification

Questions:
Answers:

This code clears the console in BOTH Windows and Unix (Although it’s actually compiled differently):

// File: clear_screen.h
#ifndef _CLEAR_SCREEN_H
#define _CLEAR_SCREEN_H
void clearScreen(void); /* Clears the screen */
#endif /* _CLEAR_SCREEN_H */
// File: clear_screen.c
#ifdef _WIN32
#include <windows.h>
void clearScreen(void) {
    HANDLE hOutput = GetStdHandle(STD_OUTPUT_HANDLE);
    COORD topLeft = {0, 0};
    DWORD dwCount, dwSize;
    CONSOLE_SCREEN_BUFFER_INFO csbi;
    GetConsoleScreenBufferInfo(hOutput, &csbi);
    dwSize = csbi.dwSize.X * csbi.dwSize.Y;
    FillConsoleOutputCharacter(hOutput, 0x20, dwSize, topLeft, &dwCount);
    FillConsoleOutputAttribute(hOutput, 0x07, dwSize, topLeft, &dwCount);
    SetConsoleCursorPosition(hStdOut, topLeft);
}
#endif /* _WIN32 */

#ifdef __unix__
#include <stdio.h>
void clearScreen(void) {
    printf("\x1B[2J");
}
#endif /* __unix__ */

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Answers:

Wouldn’t

for (int i=0;i<1000;i++){cout<<endl;}

clear the screen in all OSes?

Questions:
Answers:

This should work if you’re working on console

#include <conio.h>

int main()

{
    clrscr();
}

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