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 accross 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>

Free Pascal                                        22 jan 2006                                      grab_vcsa(1)