# phpman > man > VCS(4)

[VCS(4)](https://www.chedong.com/phpMan.php/man/VCS/4/markdown)                                Linux Programmer's Manual                               [VCS(4)](https://www.chedong.com/phpMan.php/man/VCS/4/markdown)



## NAME
       vcs, vcsa - virtual console memory

## DESCRIPTION
       _/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 con‐
       sole 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 ownership root:tty.  _/dev/vcsa[0-63]_ are  the
       same,  but  using  _unsigned_ _short_s (in host byte order) that include 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.)

       When  a  512-character  font  is  loaded, the 9th bit position can be fetched by applying the
       [**ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) **VT**___**GETHIFONTMASK**  operation  (available  in  Linux  kernels  2.6.18  and  above)  on
       _/dev/tty[1-63]_;  the value is returned in the _unsigned_ _short_ pointed to by the third [**ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown)
       argument.

       These devices replace the screendump [**ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) operations of **ioctl**___**[console**(2)](https://www.chedong.com/phpMan.php/man/console/2/markdown), so  the  system
       administrator can control access using filesystem 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**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) requests are supported.

## FILES
       _/dev/vcs[0-63]_
       _/dev/vcsa[0-63]_

## VERSIONS
       Introduced with version 1.1.92 of the Linux kernel.

## 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 vir‐
       tual console, then changes the background color there:

       #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 & ~mask) >> 8);
           printf("ch=%#03x attrib=%#02x\n", ch, attrib);
           s ^= 0x1000;
           (void) lseek(fd, -2, SEEK_CUR);
           (void) write(fd, &s, 2);
           exit(EXIT_SUCCESS);
       }

## SEE ALSO
       **ioctl**___**[console**(2)](https://www.chedong.com/phpMan.php/man/console/2/markdown), [**tty**(4)](https://www.chedong.com/phpMan.php/man/tty/4/markdown), [**ttyS**(4)](https://www.chedong.com/phpMan.php/man/ttyS/4/markdown), [**gpm**(8)](https://www.chedong.com/phpMan.php/man/gpm/8/markdown)

## COLOPHON
       This  page  is  part  of  release  5.10 of the Linux _man-pages_ project.  A description of the
       project, information about reporting bugs, and the latest version of this page, can be  found
       at <https://www.kernel.org/doc/man-pages/>.



Linux                                        2020-11-01                                       [VCS(4)](https://www.chedong.com/phpMan.php/man/VCS/4/markdown)