clear the screen

clear the screen

[kaushal]

hello all,
	Sorry for a very basic question.I would like to know how to clear the
screen from within a c program without using system("clear") or any of
the ncurses functions.Can we do this using printf?My program is in raw
mode so is there any feature available by which I can use the termios
structure for clearing the screen if it is not possible with printf.Long
ago when I used work in the dos platform I used conio.h and clrscr()
rourine.I guess I have to write that clrscr() routine's code itself.Im
working on a linux machine now.

Thanks in advance.
-kaushal.

Re: clear the screen

[J.]

On Mon, 21 Feb 2005, kaushal wrote:

> hello all,
> 	Sorry for a very basic question.I would like to know how to clear the
> screen from within a c program without using system("clear") or any of
> the ncurses functions.Can we do this using printf?My program is in raw
> mode so is there any feature available by which I can use the termios
> structure for clearing the screen if it is not possible with printf.Long
> ago when I used work in the dos platform I used conio.h and clrscr()
> rourine.I guess I have to write that clrscr() routine's code itself.Im
> working on a linux machine now.
> 
> Thanks in advance.
> -kaushal.

Don't know if this is of any help to you:
 
#include <stdio.h>

int main(void) {

 printf("\e[0m\e[2J\e[1;1H");

 return 0;
}

When the compiler is called with some warning flags it might complain
about a non-standard escape sequence, but it compiles fine and it works.
 
Goodluck & Regards,

J.

--
http://www.rdrs.net

RE: clear the screen

[Vinodkumar Nair]

>> printf("\e[0m\e[2J\e[1;1H");

How does this printf work to clear the screen?

Re: clear the screen

[YYW]

On Mon, 21 Feb 2005 15:26:51 +0530
"Vinodkumar Nair" <vinodkumar.nair@patni.com> wrote:

> >> printf("\e[0m\e[2J\e[1;1H");
> 
> How does this printf work to clear the screen?
It's ascii control character. 2J means clear the screen and
1;1H set the cursor position.

> 
> -
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-- 

Best regards,
yyw@smth

Re: clear the screen

[Darren Sessions]

system("clear");

On 2/21/05 5:12 AM, "YYW" <wu_jian@263.net> wrote:

> On Mon, 21 Feb 2005 15:26:51 +0530
> "Vinodkumar Nair" <vinodkumar.nair@patni.com> wrote:
> 
>>>> printf("\e[0m\e[2J\e[1;1H");
>> 
>> How does this printf work to clear the screen?
> It's ascii control character. 2J means clear the screen and
> 1;1H set the cursor position.
> 
>> 
>> -
>> To unsubscribe from this list: send the line "unsubscribe
>> linux-c-programming" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: clear the screen

[Ron Michael Khu]

=)
u misunderstood the original post/question by kaushal

Darren Sessions wrote:

>system("clear");
>
>On 2/21/05 5:12 AM, "YYW" <wu_jian@263.net> wrote:
>
>  
>
>>On Mon, 21 Feb 2005 15:26:51 +0530
>>"Vinodkumar Nair" <vinodkumar.nair@patni.com> wrote:
>>
>>    
>>
>>>>>printf("\e[0m\e[2J\e[1;1H");
>>>>>          
>>>>>
>>>How does this printf work to clear the screen?
>>>      
>>>
>>It's ascii control character. 2J means clear the screen and
>>1;1H set the cursor position.
>>
>>    
>>
>>>-
>>>To unsubscribe from this list: send the line "unsubscribe
>>>linux-c-programming" in
>>>the body of a message to majordomo@vger.kernel.org
>>>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>      
>>>
>
>
>-
>To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>  
>

Re: clear the screen

[Glynn Clements]

kaushal wrote:

> 	Sorry for a very basic question.I would like to know how to clear the
> screen from within a c program without using system("clear") or any of
> the ncurses functions.Can we do this using printf?My program is in raw
> mode so is there any feature available by which I can use the termios
> structure for clearing the screen if it is not possible with printf.Long
> ago when I used work in the dos platform I used conio.h and clrscr()
> rourine.I guess I have to write that clrscr() routine's code itself.Im
> working on a linux machine now.

Unix systems don't have a "screen", they have terminals. Historically,
these would be physical terminals (e.g. vt220s) connected via serial
ports. The Linux kernel uses the keyboard and the graphics card's text
mode to emulate a number of terminals, as well as supporting physical
terminals connected to a serial port (either directly or via modems)
and pseudo-terminals (used by programs which emulate terminals, e.g. 
telnetd, xterm, screen etc).

To clear the terminal's screen (assuming that it's a video terminal;
hardcopy terminals don't have a screen), you have to send the
appropriate control sequence. The exact sequence depends upon the type
of terminal (which can be determined from the value of the TERM
environment variable).

To obtain the correct control sequence, use the terminfo library to
obtain the sequence for the "clear" capability, then send that
sequence to the terminal (i.e. stdout).

See the manpage for setupterm() and tigetstr() for more information.

-- 
Glynn Clements <glynn@gclements.plus.com>

Re: clear the screen

[Progga]

On Wed, Feb 23, 2005 at 12:16:52AM +0000, Glynn Clements wrote:
> 
> See the manpage for setupterm() and tigetstr() for more information.

 Should it be like this ? 


<code>
    char *area[100], bp[2048] ;

    tgetent( bp, getenv( "TERM" )) ;
    puts( tgetstr( "cl", area )) ;
</code>

Re: clear the screen

[Glynn Clements]

Progga wrote:

> > See the manpage for setupterm() and tigetstr() for more information.
> 
>  Should it be like this ? 
> 
> 
> <code>
>     char *area[100], bp[2048] ;
> 
>     tgetent( bp, getenv( "TERM" )) ;
>     puts( tgetstr( "cl", area )) ;
> </code>

First, that's the old termcap interface; new programs should use the
terminfo interface.

Second, the use of the "area" variable is wrong. It should be
something like:

	char buf[100];
	char *area = buf;
	
	puts(tgetstr("cl", &area));

Repeated calls to tgetstr() will advance the "area" pointer, so that
"buf" will contain, in order, all of the strings retrieved by
tgetstr().

-- 
Glynn Clements <glynn@gclements.plus.com>