Getting a clear screen...

Is there a keyword and header file for getting a clear screen. For example, if you typed in a word and pressed enter, is there a function and header file that allows you to clear the screen after pressing enter...

just a thought

:)

There isn't anything that is standard to do that. What OS/compiler are you using? If you're on a Windows machine, you can use system( "cls" ). If you're on a Linux machine using bash, you can do this: cout<<"\033[H\033[J";

A quick search on Google turned up this for the Win32 console (modified to become a function and to make reading easier):

Code:

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void clearscreen( void ) {
  COORD coordScreen = { 0, 0 };
  DWORD cCharsWritten;
  CONSOLE_SCREEN_BUFFER_INFO csbi;
  DWORD dwConSize;
  HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE); // Handle to stdout
 
  // Gets the console resolution
  GetConsoleScreenBufferInfo(hConsole, &csbi);
  dwConSize = csbi.dwSize.X * csbi.dwSize.Y;
 
  // Fill every cell with spaces
  FillConsoleOutputCharacter(hConsole, TEXT(' '), dwConSize, coordScreen, &cCharsWritten);
 
  // Fill the console attributes
  FillConsoleOutputAttribute(hConsole, csbi.wAttributes, dwConSize, coordScreen, &cCharsWritten);
 
  // Sets the cursor position back to the first row and column
  SetConsoleCursorPosition(hConsole, coordScreen);
}

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Hmm. I learned something from this code too. I now know how to determine the console size. :D

Frequently asked questions

The VT100 control sequence is cool, but it should be noted that it is terminal specific. You can use the curses or ncurses library to perform a terminal independant "cls".

gg

Quote:

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Originally Posted by Finchie_88

Is there a keyword and header file for getting a clear screen. For example, if you typed in a word and pressed enter, is there a function and header file that allows you to clear the screen after pressing enter...

just a thought

:)

---

On Windows, you can enter cls on the command line, and your console window will be cleared.

On Linux, you can enter clear on the command line, and your console window will be cleared..

On windows try the following program:

Code:

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#include <stdio.h>
#include <stdlib.h>
int main()
{
  printf("This line will be wiped away by the next statement.\n");
  system("cls");
  printf("Press \"Enter\" to exit (yes, I know that's silly): ");
  getchar();
  return 0;
}

---

For linux, use "clear" instead of "cls".

Does anyone see any problems with this? Can you explain why I would do anything more complicated? (That's not a loaded question, and I don't mean to be confrontational, but I really want to know if there is anything Bad about this way of programmatically clearing the screen.)



Dave

There needs to be a standard on how to clear the screen that will work on all platforms.

It is such a commonly performed operation, yet there are about a billion ways to do it.. each one with it's own unique characteristics.

It's only "bad" if it has unwanted side effects - like not working, too slow, etc...

Personally, I don't like spawning a processes to accomplish something that can be done with just a few extra lines of code.

gg

Actually, "cls" isn't a process but I believe that "clear" is.

gg

Quote:

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Originally Posted by Codeplug

It's only "bad" if it has unwanted side effects - like not working, too slow, etc...

Personally, I don't like spawning a processes to accomplish something that can be done with just a few extra lines of code.

gg

---

Well, I certainly consider "not working" to be a bad side effect. And if I want to write a program that will run on other systems (a command-line driven text-based program whose source code can be compiled and executed under Windows or Linux, for example), then some care is obviously required, and any system() calls would be very suspect.

Compile-time switches abound in gnu code so that different platforms can be supported by a single set of source code files, but that's really hard. Make files are generated by config scripts, that use config.in files that describe and discover system characteristics, etc.

It does seem like a lot of work just to clear the stinkin' screen.

Regards,

Dave

Quote:

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Originally Posted by Codeplug

Actually, "cls" isn't a process but I believe that "clear" is.

gg

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I think this is correct: cls is a "built-in" command. In fact, I just discovered if you compile the program with system("cls"); under gcc in Windows, the program looks for an executable named cls and fails (bad side effect number 1: it doesn't work).

If you compile the program with system("clear"); under gcc in Windows and you have cygwin installed, there is an executable named clear.exe in the cywgin\bin directory, and it clears the screen. So that's a Bad thing: runs on some windows boxes but not others.

Thanks for your thoughts and feedback.

Dave

"I was born not knowing, and have only had a little time to change that, here and there."

---Richard Feynman

Quote:

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Originally Posted by The Brain

There needs to be a standard on how to clear the screen that will work on all platforms.

---

There is one way that is not platform dependant. Simply fill the screen with blank lines (the below saves a small amount of time by only having to loop five times).

Code:

---

void clearscreen( void ) {
  int index;
  for( index = 0; index < 5; index++ ) {
        printf("\n\n\n\n\n");
  }
 }

---

Quote:

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Originally Posted by Frobozz

There is one way that is not platform dependant. Simply fill the screen with blank lines (the below saves a small amount of time by only having to loop five times).

Code:

---

void clearscreen( void ) {
  int index;
  for( index = 0; index < 5; index++ ) {
        printf("\n\n\n\n\n");
  }
 }

---

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How do you know how many lines there are?

Dave

Quote:

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Originally Posted by The Brain

there are about a billion ways to do it.. each one with it's own unique characteristics.

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Sometimes I feel like I'm in a maze of twisty little passages, all alike ...

Dave

Quote:

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There is one way that is not platform dependant. Simply fill the screen with blank lines (the below saves a small amount of time by only having to loop five times).

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It also leaves the prompt at the bottom of the terminal - not so cool

~/