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screendump(1) [minix man page]

SCREENDUMP(1)                                                      Linux Console                                                     SCREENDUMP(1)

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)

Check Out this Related Man Page

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

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 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) argument. These devices replace the screendump ioctl(2) operations 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(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> #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 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 ", 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
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