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RedHat 9 (Linux i386) - man page for vcs (redhat section 4)

VCS(4)				    Linux Programmer's Manual				   VCS(4)

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

	    int main() {
		 int fd;
		 struct {char lines, cols, x, y;} scrn;
		 char ch, attrib;

		 fd = open("/dev/vcsa2", O_RDWR);
		 (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='%c' 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
       console(4), tty(4), ttys(4), selection(1)

Linux					    1995-02-19					   VCS(4)


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