vcs


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 using unsigned
       shorts (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) 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) argu-
       ment.

       These devices replace the screendump ioctl(2) operations of console(4),
       so  the  system administrator can control access using file system per-
       missions.

       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) requests are supported.

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

VERSIONS
       Introduced with version 1.1.92 of the Linux kernel.

EXAMPLE
       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 charac-
       ters, 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>
           unsigned short s;
           unsigned short mask;
           unsigned char ch, attrib;

           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), 0);
           (void) read(fd, &s, 2);
           ch = s & 0xff;
           if (attrib & mask)
               ch |= 0x100;
           attrib = ((s & ~mask) >> 8);
           printf("ch='%c' attrib=0x%02x\n", ch, attrib);
           attrib ^= 0x10;
           (void) lseek(fd, -1, 1);
           (void) write(fd, &attrib, 1);
           exit(EXIT_SUCCESS);
       }

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

COLOPHON
       This  page  is  part of release 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.



Linux                             2007-12-17                            VCS(4)
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