NAME

       grab_vcsa - Linux console vcsa grabber

SYNOPSIS

       grab_vcsa

DESCRIPTION

       The  Linux console allows text mode video buffer access^. For each tty device (/dev/tty0..31) there exist
       two devices (/dev/vcs0..31) and (/dev/vcsa0..31).  These devices are two different representations of the
       content of the console.

       When  you  login on the Linux console, your tty device is changed owner to you, so you can read/write it.
       When you logout it is takes from you. This does not happen with the vcs and vcsa devices, i.e. you cannot
       access the video buffer of your own tty.

       Unfortunately  there  is  a  lot  of  reason  to  use the text mode video buffer. For instance, it is not
       possible to get access to the full 256 characters the VGA adapter can display without using the text mode
       video  buffer  (Linux  emulates  the  vt100  character  set which does not have all VGA characters). This
       annoyance severely limits the porting possibilities to Linux of software that  was  written  with  a  VGA
       character set in mind.

       grab_vcsa is a setuid root program that, when called will change the owner of the vcs and vcsa devices to
       you, after a series of security checks have been performed.

       It is not necessary to change the permissions back again (this would be pointless since a user could kill
       a  imaginary  release_vcsa program before it can do its work). The permissions are automatically reverted
       on logout.

       grab_vcsa is used by the Free Pascal video unit. The video unit allows programmers  to  develop  portable
       programs  across  Dos,  Linux,  FreeBSD,  Windows,  OS/2 and other operating systems while they can still
       assume being able to use the full VGA character set.

RETURN CODES

       grab_vcsa has the following return codes:

       0      Success

       1      You are not running on the Linux console

       2      Error while statting tty.

       3      Error while executing chown.

       4      Error while executing chmod.

       4      You do not own your own tty.

AUTHOR

       Daniel Mantione <daniel.mantione@freepascal.org>