Adding upstream version 6.05.01.upstream/6.05.01

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 172 insertions, 0 deletions

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+.\" Copyright (c) 1995 James R. Van Zandt <jrv@vanzandt.mv.com>
+.\" Sat Feb 18 09:11:07 EST 1995
+.\"
+.\" SPDX-License-Identifier: GPL-2.0-or-later
+.\"
+.\" Modified, Sun Feb 26 15:08:05 1995, faith@cs.unc.edu
+.\" 2007-12-17, Samuel Thibault <samuel.thibault@ens-lyon.org>:
+.\"     document the VT_GETHIFONTMASK ioctl
+.\" "
+.TH vcs 4 2023-05-03 "Linux man-pages 6.05.01"
+.SH NAME
+vcs, vcsa \- virtual console memory
+.SH DESCRIPTION
+.I /dev/vcs0
+is a character device with major number 7 and minor number
+0, usually with mode 0644 and ownership root:tty.
+It refers to the memory of the currently
+displayed virtual console terminal.
+.PP
+.I /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 ownership root:tty.
+.I /dev/vcsa[0\-63]
+are the same, but
+using
+.IR "unsigned short" s
+(in host byte order) that include attributes,
+and prefixed with four bytes giving the screen
+dimensions and cursor position:
+.IR lines ,
+.IR columns ,
+.IR x ,
+.IR y .
+.RI ( x
+=
+.I y
+= 0 at the top left corner of the screen.)
+.PP
+When a 512-character font is loaded,
+the 9th bit position can be fetched by applying the
+.BR ioctl (2)
+.B VT_GETHIFONTMASK
+operation
+(available since Linux 2.6.18)
+on
+.IR /dev/tty[1\-63] ;
+the value is returned in the
+.I "unsigned short"
+pointed to by the third
+.BR ioctl (2)
+argument.
+.PP
+These devices replace the screendump
+.BR ioctl (2)
+operations of
+.BR ioctl_console (2),
+so the system
+administrator can control access using filesystem permissions.
+.PP
+The devices for the first eight virtual consoles may be created by:
+.PP
+.in +4n
+.EX
+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*
+.EE
+.in
+.PP
+No
+.BR ioctl (2)
+requests are supported.
+.SH FILES
+.I /dev/vcs[0\-63]
+.br
+.I /dev/vcsa[0\-63]
+.\" .SH AUTHOR
+.\" Andries Brouwer <aeb@cwi.nl>
+.SH VERSIONS
+Introduced with Linux 1.1.92.
+.SH EXAMPLES
+You may do a screendump on vt3 by switching to vt1 and typing
+.PP
+.in +4n
+.EX
+cat /dev/vcs3 >foo
+.EE
+.in
+.PP
+Note that the output does not contain
+newline characters, so some processing may be required, like
+in
+.PP
+.in +4n
+.EX
+fold \-w 81 /dev/vcs3 | lpr
+.EE
+.in
+.PP
+or (horrors)
+.PP
+.in +4n
+.EX
+setterm \-dump 3 \-file /proc/self/fd/1
+.EE
+.in
+.PP
+The
+.I /dev/vcsa0
+device is used for Braille support.
+.PP
+This program displays the character and screen attributes under the
+cursor of the second virtual console, then changes the background color
+there:
+.PP
+.EX
+#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 attrib;
+    int ch;
+\&
+    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), SEEK_SET);
+    (void) read(fd, &s, 2);
+    ch = s & 0xff;
+    if (s & mask)
+        ch |= 0x100;
+    attrib = ((s & \[ti]mask) >> 8);
+    printf("ch=%#03x attrib=%#02x\en", ch, attrib);
+    s \[ha]= 0x1000;
+    (void) lseek(fd, \-2, SEEK_CUR);
+    (void) write(fd, &s, 2);
+    exit(EXIT_SUCCESS);
+}
+.EE
+.SH SEE ALSO
+.BR ioctl_console (2),
+.BR tty (4),
+.BR ttyS (4),
+.BR gpm (8)