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vcstime(8) [linux man page]

VCSTIME(8)							Linux User's Manual							VCSTIME(8)

NAME
vcstime - Show time in upper right hand corner of the console screen SYNOPSIS
vcstime DESCRIPTION
vcstime shows the current time in the upper right-hand corner of the console screen. This simple program shows the current time in the corner of the console screen. It needs to be run by root, in order to have write permissions to /dev/vcsa AUTHORS
vcstime was written by Andries Brouwer, based on a suggestion by Miguel de Icaza. This manual page was Written by Alastair McKinstry, Debian, Jan 2003. Console tools 22 Jan 2003 VCSTIME(8)

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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 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 characters, so some processing may be required, like in old -w 81 /dev/vcs3 | lpr or (horrors) xetterm -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 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2007-12-17 VCS(4)
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