screendump(1) [linux man page]

SCREENDUMP(1)							   Linux Console						     SCREENDUMP(1)

NAME

       screendump - dump the contents of a virtual console to stdout

SYNOPSIS

       screendump [ N ]

DESCRIPTION

       The screendump command dumps the contents of virtual console N , (or the current console if N is omitted) to standard out.

       Just saying
	      cat /dev/vcsN
       has a similar effect.

NOTES

       For  security  reasons,	screendump uses linux devices "virtual console screen" and "virtual console screen with attributes" to give access
       for screendump.

       Ensure these files exist, using

	      cd /dev for i in 0 1 2 3 ...; do
		   mknod vcs$i c 7 $i
		   mknod vcsa$i c 7 `expr 128 + $i`
	      done

       (filling in the ellipses) and give the device files appropriate permissions, or run screendump as root.

SEE ALSO

       setterm(1)

								    2002-02-24							     SCREENDUMP(1)

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 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 <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
", 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)