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NAME

       vcs, vcsa - virtual console memory

DESCRIPTION

       /dev/vcs0 is a character device with major number 7 and minor number 0,
       usually of mode 0644 and owner root.tty.  It refers to  the  memory  of
       the currently displayed virtual console terminal.

       /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  owner  root.tty.   /dev/vcsa[0-63]  are  the  same,  but including
       attributes, and prefixed with four bytes giving the  screen  dimensions
       and  cursor position: lines, columns, x, y.  (x = y = 0 at the top left
       corner of the screen.)

       These replace the  screendump  ioctls  of  console(4),  so  the  system
       administrator can control access using file system permissions.

       The devices for the first eight virtual consoles may be created by:

            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*

       No ioctl() requests are supported.

EXAMPLES

       You  may  do  a  screendump  on  vt3 by switching to vt1 and typing cat
       /dev/vcs3  >foo.  Note  that  the  output  does  not  contain   newline
       characters,  so  some  processing  may  be required, like in fold -w 81
       /dev/vcs3 | lpr or (horrors) setterm -dump 3 -file /proc/self/fd/1.

       The /dev/vcsa0 device is used for Braille support.

       This program displays the character and  screen  attributes  under  the
       cursor of the second virtual console, then changes the background color
       there:

            #include <unistd.h>
            #include <stdlib.h>
            #include <stdio.h>
            #include <fcntl.h>

            int main() {
                 int fd;
                 char *device = "/dev/vcsa2";
                 struct {unsigned char lines, cols, x, y;} scrn;
                 char ch, attrib;

                 fd = open(device, O_RDWR);
                 if (fd < 0) {
                      perror(device);
                      exit(1);
                 }
                 (void)read(fd, &scrn, 4);
                 (void)lseek(fd, 4 + 2*(scrn.y*scrn.cols + scrn.x), 0);
                 (void)read(fd, &ch, 1);
                 (void)read(fd, &attrib, 1);
                 printf("ch=ā€™%cā€™ attrib=0x%02x\n", ch, attrib);
                 attrib ^= 0x10;
                 (void)lseek(fd, -1, 1);
                 (void)write(fd, &attrib, 1);
                 return 0;
            }

FILES

       /dev/vcs[0-63]
       /dev/vcsa[0-63]

AUTHOR

       Andries Brouwer <aeb@cwi.nl>

HISTORY

       Introduced with version 1.1.92 of the Linux kernel.

SEE ALSO

       gpm(8), console(4), tty(4), ttyS(4)