Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

screendu(8) [minix man page]

SCREENDUMP(8)						      System Manager's Manual						     SCREENDUMP(8)

screendump - write current console screen to standard output SYNOPSIS
screendump DESCRIPTION
Screendump prints the contents of the console screen to standard output. It does this by reading the screen memory, skipping over attribute bytes, omitting trailing blanks and inserting a newline character at the end of each line. NOTES
The most common use of screendump is with output redirected to a file. This allows screen displays (including output of F-keys) to be cap- tured for inclusion in other documents. This version is for IBM-PC architecture only. BUGS
A network user captures an image of the main console, not his or her own screen. The output will usually not be what you expect if the display is in hardware scrolling mode, since in that mode the order of the lines in screen memory may not be the same as what appears on the screen. If you expect to use screendump to send notes to someone about problems that occur while using MINIX you must remember to tog- gle to software scrolling before you make the dump. It will also be necessary to use su, because /dev/mem is normally not world readable. AUTHOR
Kees J. Bot ( SCREENDUMP(8)

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
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at Linux 2007-12-17 VCS(4)
Man Page