These replace the screendump ioctls of console(4), 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() requests are supported.

EXAMPLES

You can do a screendump on vt3 by switching to vt1 and typing cat /dev/vcs3 >foo.

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

#include <unistd.h>

#include <stdio.h>

#include <fcntl.h>



void 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);

}

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, 19 February 1995