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-.\" Copyright (c) 1995 James R. Van Zandt <jrv@vanzandt.mv.com>
-.\" Sat Feb 18 09:11:07 EST 1995
-.\"
-.\" SPDX-License-Identifier: GPL-2.0-or-later
-.\"
-.\" Modified, Sun Feb 26 15:08:05 1995, faith@cs.unc.edu
-.\" 2007-12-17, Samuel Thibault <samuel.thibault@ens-lyon.org>:
-.\" document the VT_GETHIFONTMASK ioctl
-.\" "
-.TH vcs 4 2023-10-31 "Linux man-pages 6.7"
-.SH NAME
-vcs, vcsa \- virtual console memory
-.SH DESCRIPTION
-.I /dev/vcs0
-is a character device with major number 7 and minor number
-0, usually with mode 0644 and ownership root:tty.
-It refers to the memory of the currently
-displayed virtual console terminal.
-.P
-.I /dev/vcs[1\-63]
-are character devices for virtual console
-terminals, they have major number 7 and minor number 1 to 63, usually
-mode 0644 and ownership root:tty.
-.I /dev/vcsa[0\-63]
-are the same, but
-using
-.IR "unsigned short" s
-(in host byte order) that include attributes,
-and prefixed with four bytes giving the screen
-dimensions and cursor position:
-.IR lines ,
-.IR columns ,
-.IR x ,
-.IR y .
-.RI ( x
-=
-.I y
-= 0 at the top left corner of the screen.)
-.P
-When a 512-character font is loaded,
-the 9th bit position can be fetched by applying the
-.BR ioctl (2)
-.B VT_GETHIFONTMASK
-operation
-(available since Linux 2.6.18)
-on
-.IR /dev/tty[1\-63] ;
-the value is returned in the
-.I "unsigned short"
-pointed to by the third
-.BR ioctl (2)
-argument.
-.P
-These devices replace the screendump
-.BR ioctl (2)
-operations of
-.BR ioctl_console (2),
-so the system
-administrator can control access using filesystem permissions.
-.P
-The devices for the first eight virtual consoles may be created by:
-.P
-.in +4n
-.EX
-for x in 0 1 2 3 4 5 6 7 8; do
- mknod \-m 644 /dev/vcs$x c 7 $x;
- mknod \-m 644 /dev/vcsa$x c 7 $[$x+128];
-done
-chown root:tty /dev/vcs*
-.EE
-.in
-.P
-No
-.BR ioctl (2)
-requests are supported.
-.SH FILES
-.I /dev/vcs[0\-63]
-.br
-.I /dev/vcsa[0\-63]
-.\" .SH AUTHOR
-.\" Andries Brouwer <aeb@cwi.nl>
-.SH VERSIONS
-Introduced with Linux 1.1.92.
-.SH EXAMPLES
-You may do a screendump on vt3 by switching to vt1 and typing
-.P
-.in +4n
-.EX
-cat /dev/vcs3 >foo
-.EE
-.in
-.P
-Note that the output does not contain
-newline characters, so some processing may be required, like
-in
-.P
-.in +4n
-.EX
-fold \-w 81 /dev/vcs3 | lpr
-.EE
-.in
-.P
-or (horrors)
-.P
-.in +4n
-.EX
-setterm \-dump 3 \-file /proc/self/fd/1
-.EE
-.in
-.P
-The
-.I /dev/vcsa0
-device is used for Braille support.
-.P
-This program displays the character and screen attributes under the
-cursor of the second virtual console, then changes the background color
-there:
-.P
-.EX
-#include <unistd.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <fcntl.h>
-#include <sys/ioctl.h>
-#include <linux/vt.h>
-\&
-int
-main(void)
-{
- int fd;
- char *device = "/dev/vcsa2";
- char *console = "/dev/tty2";
- struct {unsigned char lines, cols, x, y;} scrn;
- unsigned short s;
- unsigned short mask;
- unsigned char attrib;
- int ch;
-\&
- fd = open(console, O_RDWR);
- if (fd < 0) {
- perror(console);
- exit(EXIT_FAILURE);
- }
- if (ioctl(fd, VT_GETHIFONTMASK, &mask) < 0) {
- perror("VT_GETHIFONTMASK");
- exit(EXIT_FAILURE);
- }
- (void) close(fd);
- fd = open(device, O_RDWR);
- if (fd < 0) {
- perror(device);
- exit(EXIT_FAILURE);
- }
- (void) read(fd, &scrn, 4);
- (void) lseek(fd, 4 + 2*(scrn.y*scrn.cols + scrn.x), SEEK_SET);
- (void) read(fd, &s, 2);
- ch = s & 0xff;
- if (s & mask)
- ch |= 0x100;
- attrib = ((s & \[ti]mask) >> 8);
- printf("ch=%#03x attrib=%#02x\en", ch, attrib);
- s \[ha]= 0x1000;
- (void) lseek(fd, \-2, SEEK_CUR);
- (void) write(fd, &s, 2);
- exit(EXIT_SUCCESS);
-}
-.EE
-.SH SEE ALSO
-.BR ioctl_console (2),
-.BR tty (4),
-.BR ttyS (4),
-.BR gpm (8)