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Diffstat (limited to 'man4/vcs.4')
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diff --git a/man4/vcs.4 b/man4/vcs.4 new file mode 100644 index 000000000..de5e352a1 --- /dev/null +++ b/man4/vcs.4 @@ -0,0 +1,114 @@ +.\" Copyright (c) 1995 James R. Van Zandt <jrv@vanzandt.mv.com> +.\" Sat Feb 18 09:11:07 EST 1995 +.\" +.\" This is free documentation; you can redistribute it and/or +.\" modify it under the terms of the GNU General Public License as +.\" published by the Free Software Foundation; either version 2 of +.\" the License, or (at your option) any later version. +.\" +.\" The GNU General Public License's references to "object code" +.\" and "executables" are to be interpreted as the output of any +.\" document formatting or typesetting system, including +.\" intermediate and printed output. +.\" +.\" This manual is distributed in the hope that it will be useful, +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +.\" GNU General Public License for more details. +.\" +.\" You should have received a copy of the GNU General Public +.\" License along with this manual; if not, write to the Free +.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, +.\" USA. +.\" +.\" Modified, Sun Feb 26 15:08:05 1995, faith@cs.unc.edu +.\" " +.TH VCS 4 1995-02-19 "Linux" "Linux Programmer's Manual" +.SH NAME +vcs, vcsa \- virtual console memory +.SH DESCRIPTION +\fB/dev/vcs0\fP 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. +.LP +\fB/dev/vcs[1-63]\fP 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. \fB/dev/vcsa[0-63]\fP are the same, but +including attributes, and prefixed with four bytes giving the screen +dimensions and cursor position: \fIlines\fP, \fIcolumns\fP, \fIx\fP, \fIy\fP. +(\fIx\fP = \fIy\fP = 0 at the top left corner of the screen.) +.PP +These replace the screendump +.IR ioctl s +of \fBconsole\fP(4), so the system +administrator can control access using file system permissions. +.PP +The devices for the first eight virtual consoles may be created by: + +.nf + 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* +.fi + +No +.IR ioctl () +requests are supported. +.SH EXAMPLES +You may do a screendump on vt3 by switching to vt1 and typing +\fIcat /dev/vcs3 >foo\fP. Note that the output does not contain +newline characters, so some processing may be required, like +in \fIfold -w 81 /dev/vcs3 | lpr\fP or (horrors) +\fIsetterm -dump 3 -file /proc/self/fd/1\fP. +.LP +The \fI/dev/vcsa0\fP 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: + +.nf + #include <unistd.h> + #include <stdlib.h> + #include <stdio.h> + #include <fcntl.h> + + int main() { + int fd; + char *device = "/dev/vcsa2"; + struct {unsigned char lines, cols, x, y;} scrn; + char ch, attrib; + + fd = open(device, O_RDWR); + if (fd < 0) { + perror(device); + exit(1); + } + (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); + return 0; + } +.fi + +.SH FILES +/dev/vcs[0-63] +.br +/dev/vcsa[0-63] +.SH AUTHOR +Andries Brouwer <aeb@cwi.nl> +.SH HISTORY +Introduced with version 1.1.92 of the Linux kernel. +.SH "SEE ALSO" +.BR selection (1), +.BR console (4), +.BR tty (4), +.BR ttys (4) |