The OpenNET Project / Index page

[ новости/++ | форум | wiki | теги | ]

Интерактивная система просмотра системных руководств (man-ов)

 ТемаНаборКатегория 
 
 [Cписок руководств | Печать]

vcsa (4)
  • vcsa (4) ( Русские man: Специальные файлы /dev/* )
  • >> vcsa (4) ( Linux man: Специальные файлы /dev/* )
  •  

    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 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=aq%caq attrib=0x%02x\n", 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 3.14 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/.


     

    Index

    NAME
    DESCRIPTION
    FILES
    VERSIONS
    EXAMPLE
    SEE ALSO
    COLOPHON


    Поиск по тексту MAN-ов: 



      Закладки на сайте
      Проследить за страницей
    Created 1996-2017 by Maxim Chirkov  
    ДобавитьРекламаВебмастеруГИД  
    Hosting by Ihor