System("clear") error

Applications Programming
1

I was trying to run a connect four game in C++, but I got this error while compiling in Cygwin:

c4.cpp: In member function �void connectFour::clearScreen()�:
c4.cpp:162:35: error: �system� was not declared in this scope
                     system("clear");
                                   ^

The coder left this above the part using "system("clear")":

//Set for OSX currently - Change the inner system call for Windows or Linux

How can I solve this problem?

2

At the top of the program,

#include <stdlib.h>

That will fix the error. Whether it will work I am less certain. The contents of system() are system-dependent. cygwin might have a clear utility or might not. If this was a Windows commandline program rather than cygwin you'd probably do system("CLS");

3

Adding to Corona's reply...
I am not sure that clear exists in CygWin.
If it does it will be "clear.exe" inside the "/bin" folder(/drawer/directory)...
You could try this as an alternative:-

#include <cstdlib>

int main()
{
	system("printf '\033[2J\033[H'");        // This is the important line...
	return 0;
}

Compiled inside OSX 10.7.5, default bash terminal...

EDIT:

Forgot to add that compiling this under OSX required:-

#include <cstdlib>
4

You do not need system() to print escape codes in C:

printf("\x1b[2J\x1b[H");  fflush(stdout);
1 Like
5

Remember! To use the "printf()" function then......

#include <stdio.h>

OR

#include <cstdio>

......will be needed...
Or else this error will result:-

AMIGA:barrywalker~> g++ clear.cpp
clear.cpp: In function �int main()':
clear.cpp:8: error: �printf' was not declared in this scope
AMIGA:barrywalker~> _
1 Like
6

When you call system("some_command") -
You are invoking a new process, and the new process may not be running the same shell you connected with. In cygwin that shell is: /bin/sh, which is bash. The other point is it may not be able to find command executables like /bin/clear unless you add the full file name.