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NAME
ioctl_console - ioctls for console terminal and virtual consoles
DESCRIPTION
The following Linux-specific ioctl(2) operations are supported for console terminals and virtual
consoles. Each operation requires a third argument, assumed here to be argp.
KDGETLED
Get state of LEDs. argp points to a char. The lower three bits of *argp are set to the state of
the LEDs, as follows:
LED_CAP 0x04 caps lock led
LED_NUM 0x02 num lock led
LED_SCR 0x01 scroll lock led
KDSETLED
Set the LEDs. The LEDs are set to correspond to the lower three bits of the unsigned long integer
in argp. However, if a higher order bit is set, the LEDs revert to normal: displaying the state
of the keyboard functions of caps lock, num lock, and scroll lock.
Before Linux 1.1.54, the LEDs just reflected the state of the corresponding keyboard flags, and
KDGETLED/KDSETLED would also change the keyboard flags. Since Linux 1.1.54 the LEDs can be made to
display arbitrary information, but by default they display the keyboard flags. The following two ioctls
are used to access the keyboard flags.
KDGKBLED
Get keyboard flags CapsLock, NumLock, ScrollLock (not lights). argp points to a char which is set
to the flag state. The low order three bits (mask 0x7) get the current flag state, and the low
order bits of the next nibble (mask 0x70) get the default flag state. (Since Linux 1.1.54.)
KDSKBLED
Set keyboard flags CapsLock, NumLock, ScrollLock (not lights). argp is an unsigned long integer
that has the desired flag state. The low order three bits (mask 0x7) have the flag state, and the
low order bits of the next nibble (mask 0x70) have the default flag state. (Since Linux 1.1.54.)
KDGKBTYPE
Get keyboard type. This returns the value KB_101, defined as 0x02.
KDADDIO
Add I/O port as valid. Equivalent to ioperm(arg,1,1).
KDDELIO
Delete I/O port as valid. Equivalent to ioperm(arg,1,0).
KDENABIO
Enable I/O to video board. Equivalent to ioperm(0x3b4, 0x3df-0x3b4+1, 1).
KDDISABIO
Disable I/O to video board. Equivalent to ioperm(0x3b4, 0x3df-0x3b4+1, 0).
KDSETMODE
Set text/graphics mode. argp is an unsigned integer containing one of:
KD_TEXT 0x00
KD_GRAPHICS 0x01
KDGETMODE
Get text/graphics mode. argp points to an int which is set to one of the values shown above for
KDSETMODE.
KDMKTONE
Generate tone of specified length. The lower 16 bits of the unsigned long integer in argp specify
the period in clock cycles, and the upper 16 bits give the duration in msec. If the duration is
zero, the sound is turned off. Control returns immediately. For example, argp = (125<<16) +
0x637 would specify the beep normally associated with a ctrl-G. (Thus since Linux 0.99pl1; broken
in Linux 2.1.49-50.)
KIOCSOUND
Start or stop sound generation. The lower 16 bits of argp specify the period in clock cycles
(that is, argp = 1193180/frequency). argp = 0 turns sound off. In either case, control returns
immediately.
GIO_CMAP
Get the current default color map from kernel. argp points to a 48-byte array. (Since Linux
1.3.3.)
PIO_CMAP
Change the default text-mode color map. argp points to a 48-byte array which contains, in order,
the Red, Green, and Blue values for the 16 available screen colors: 0 is off, and 255 is full
intensity. The default colors are, in order: black, dark red, dark green, brown, dark blue, dark
purple, dark cyan, light grey, dark grey, bright red, bright green, yellow, bright blue, bright
purple, bright cyan, and white. (Since Linux 1.3.3.)
GIO_FONT
Gets 256-character screen font in expanded form. argp points to an 8192-byte array. Fails with
error code EINVAL if the currently loaded font is a 512-character font, or if the console is not
in text mode.
GIO_FONTX
Gets screen font and associated information. argp points to a struct consolefontdesc (see
PIO_FONTX). On call, the charcount field should be set to the maximum number of characters that
would fit in the buffer pointed to by chardata. On return, the charcount and charheight are
filled with the respective data for the currently loaded font, and the chardata array contains the
font data if the initial value of charcount indicated enough space was available; otherwise the
buffer is untouched and errno is set to ENOMEM. (Since Linux 1.3.1.)
PIO_FONT
Sets 256-character screen font. Load font into the EGA/VGA character generator. argp points to
an 8192-byte map, with 32 bytes per character. Only the first N of them are used for an 8xN font
(0 < N <= 32). This call also invalidates the Unicode mapping.
PIO_FONTX
Sets screen font and associated rendering information. argp points to a
struct consolefontdesc {
unsigned short charcount; /* characters in font
(256 or 512) */
unsigned short charheight; /* scan lines per
character (1-32) */
char *chardata; /* font data in
expanded form */
};
If necessary, the screen will be appropriately resized, and SIGWINCH sent to the appropriate
processes. This call also invalidates the Unicode mapping. (Since Linux 1.3.1.)
PIO_FONTRESET
Resets the screen font, size, and Unicode mapping to the bootup defaults. argp is unused, but
should be set to NULL to ensure compatibility with future versions of Linux. (Since Linux
1.3.28.)
GIO_SCRNMAP
Get screen mapping from kernel. argp points to an area of size E_TABSZ, which is loaded with the
font positions used to display each character. This call is likely to return useless information
if the currently loaded font is more than 256 characters.
GIO_UNISCRNMAP
Get full Unicode screen mapping from kernel. argp points to an area of size
E_TABSZ*sizeof(unsigned short), which is loaded with the Unicodes each character represent. A
special set of Unicodes, starting at U+F000, are used to represent "direct to font" mappings.
(Since Linux 1.3.1.)
PIO_SCRNMAP
Loads the "user definable" (fourth) table in the kernel which maps bytes into console screen
symbols. argp points to an area of size E_TABSZ.
PIO_UNISCRNMAP
Loads the "user definable" (fourth) table in the kernel which maps bytes into Unicodes, which are
then translated into screen symbols according to the currently loaded Unicode-to-font map.
Special Unicodes starting at U+F000 can be used to map directly to the font symbols. (Since Linux
1.3.1.)
GIO_UNIMAP
Get Unicode-to-font mapping from kernel. argp points to a
struct unimapdesc {
unsigned short entry_ct;
struct unipair *entries;
};
where entries points to an array of
struct unipair {
unsigned short unicode;
unsigned short fontpos;
};
(Since Linux 1.1.92.)
PIO_UNIMAP
Put unicode-to-font mapping in kernel. argp points to a struct unimapdesc. (Since Linux 1.1.92)
PIO_UNIMAPCLR
Clear table, possibly advise hash algorithm. argp points to a
struct unimapinit {
unsigned short advised_hashsize; /* 0 if no opinion */
unsigned short advised_hashstep; /* 0 if no opinion */
unsigned short advised_hashlevel; /* 0 if no opinion */
};
(Since Linux 1.1.92.)
KDGKBMODE
Gets current keyboard mode. argp points to a long which is set to one of these:
K_RAW 0x00 /* Raw (scancode) mode */
K_XLATE 0x01 /* Translate keycodes using keymap */
K_MEDIUMRAW 0x02 /* Medium raw (scancode) mode */
K_UNICODE 0x03 /* Unicode mode */
K_OFF 0x04 /* Disabled mode; since Linux 2.6.39 */
KDSKBMODE
Sets current keyboard mode. argp is a long equal to one of the values shown for KDGKBMODE.
KDGKBMETA
Gets meta key handling mode. argp points to a long which is set to one of these:
K_METABIT 0x03 set high order bit
K_ESCPREFIX 0x04 escape prefix
KDSKBMETA
Sets meta key handling mode. argp is a long equal to one of the values shown above for KDGKBMETA.
KDGKBENT
Gets one entry in key translation table (keycode to action code). argp points to a
struct kbentry {
unsigned char kb_table;
unsigned char kb_index;
unsigned short kb_value;
};
with the first two members filled in: kb_table selects the key table (0 <= kb_table <
MAX_NR_KEYMAPS), and kb_index is the keycode (0 <= kb_index < NR_KEYS). kb_value is set to the
corresponding action code, or K_HOLE if there is no such key, or K_NOSUCHMAP if kb_table is
invalid.
KDSKBENT
Sets one entry in translation table. argp points to a struct kbentry.
KDGKBSENT
Gets one function key string. argp points to a
struct kbsentry {
unsigned char kb_func;
unsigned char kb_string[512];
};
kb_string is set to the (null-terminated) string corresponding to the kb_functh function key
action code.
KDSKBSENT
Sets one function key string entry. argp points to a struct kbsentry.
KDGKBDIACR
Read kernel accent table. argp points to a
struct kbdiacrs {
unsigned int kb_cnt;
struct kbdiacr kbdiacr[256];
};
where kb_cnt is the number of entries in the array, each of which is a
struct kbdiacr {
unsigned char diacr;
unsigned char base;
unsigned char result;
};
KDGETKEYCODE
Read kernel keycode table entry (scan code to keycode). argp points to a
struct kbkeycode {
unsigned int scancode;
unsigned int keycode;
};
keycode is set to correspond to the given scancode. (89 <= scancode <= 255 only. For 1 <=
scancode <= 88, keycode==scancode.) (Since Linux 1.1.63.)
KDSETKEYCODE
Write kernel keycode table entry. argp points to a struct kbkeycode. (Since Linux 1.1.63.)
KDSIGACCEPT
The calling process indicates its willingness to accept the signal argp when it is generated by
pressing an appropriate key combination. (1 <= argp <= NSIG). (See spawn_console() in
linux/drivers/char/keyboard.c.)
VT_OPENQRY
Returns the first available (non-opened) console. argp points to an int which is set to the
number of the vt (1 <= *argp <= MAX_NR_CONSOLES).
VT_GETMODE
Get mode of active vt. argp points to a
struct vt_mode {
char mode; /* vt mode */
char waitv; /* if set, hang on writes if not active */
short relsig; /* signal to raise on release op */
short acqsig; /* signal to raise on acquisition */
short frsig; /* unused (set to 0) */
};
which is set to the mode of the active vt. mode is set to one of these values:
VT_AUTO auto vt switching
VT_PROCESS process controls switching
VT_ACKACQ acknowledge switch
VT_SETMODE
Set mode of active vt. argp points to a struct vt_mode.
VT_GETSTATE
Get global vt state info. argp points to a
struct vt_stat {
unsigned short v_active; /* active vt */
unsigned short v_signal; /* signal to send */
unsigned short v_state; /* vt bit mask */
};
For each vt in use, the corresponding bit in the v_state member is set. (Linux 1.0 through Linux
1.1.92.)
VT_RELDISP
Release a display.
VT_ACTIVATE
Switch to vt argp (1 <= argp <= MAX_NR_CONSOLES).
VT_WAITACTIVE
Wait until vt argp has been activated.
VT_DISALLOCATE
Deallocate the memory associated with vt argp. (Since Linux 1.1.54.)
VT_RESIZE
Set the kernel's idea of screensize. argp points to a
struct vt_sizes {
unsigned short v_rows; /* # rows */
unsigned short v_cols; /* # columns */
unsigned short v_scrollsize; /* no longer used */
};
Note that this does not change the videomode. See resizecons(8). (Since Linux 1.1.54.)
VT_RESIZEX
Set the kernel's idea of various screen parameters. argp points to a
struct vt_consize {
unsigned short v_rows; /* number of rows */
unsigned short v_cols; /* number of columns */
unsigned short v_vlin; /* number of pixel rows
on screen */
unsigned short v_clin; /* number of pixel rows
per character */
unsigned short v_vcol; /* number of pixel columns
on screen */
unsigned short v_ccol; /* number of pixel columns
per character */
};
Any parameter may be set to zero, indicating "no change", but if multiple parameters are set, they
must be self-consistent. Note that this does not change the videomode. See resizecons(8).
(Since Linux 1.3.3.)
The action of the following ioctls depends on the first byte in the struct pointed to by argp, referred
to here as the subcode. These are legal only for the superuser or the owner of the current terminal.
Symbolic subcodes are available in <linux/tiocl.h> since Linux 2.5.71.
TIOCLINUX, subcode=0
Dump the screen. Disappeared in Linux 1.1.92. (With Linux 1.1.92 or later, read from /dev/vcsN
or /dev/vcsaN instead.)
TIOCLINUX, subcode=1
Get task information. Disappeared in Linux 1.1.92.
TIOCLINUX, subcode=TIOCL_SETSEL
Set selection. argp points to a
struct {
char subcode;
short xs, ys, xe, ye;
short sel_mode;
};
xs and ys are the starting column and row. xe and ye are the ending column and row. (Upper left
corner is row=column=1.) sel_mode is 0 for character-by-character selection, 1 for word-by-word
selection, or 2 for line-by-line selection. The indicated screen characters are highlighted and
saved in a kernel buffer.
Since Linux 6.7, using this subcode requires the CAP_SYS_ADMIN capability.
TIOCLINUX, subcode=TIOCL_PASTESEL
Paste selection. The characters in the selection buffer are written to fd.
Since Linux 6.7, using this subcode requires the CAP_SYS_ADMIN capability.
TIOCLINUX, subcode=TIOCL_UNBLANKSCREEN
Unblank the screen.
TIOCLINUX, subcode=TIOCL_SELLOADLUT
Sets contents of a 256-bit look up table defining characters in a "word", for word-by-word
selection. (Since Linux 1.1.32.)
Since Linux 6.7, using this subcode requires the CAP_SYS_ADMIN capability.
TIOCLINUX, subcode=TIOCL_GETSHIFTSTATE
argp points to a char which is set to the value of the kernel variable shift_state. (Since Linux
1.1.32.)
TIOCLINUX, subcode=TIOCL_GETMOUSEREPORTING
argp points to a char which is set to the value of the kernel variable report_mouse. (Since Linux
1.1.33.)
TIOCLINUX, subcode=8
Dump screen width and height, cursor position, and all the character-attribute pairs. (Linux
1.1.67 through Linux 1.1.91 only. With Linux 1.1.92 or later, read from /dev/vcsa* instead.)
TIOCLINUX, subcode=9
Restore screen width and height, cursor position, and all the character-attribute pairs. (Linux
1.1.67 through Linux 1.1.91 only. With Linux 1.1.92 or later, write to /dev/vcsa* instead.)
TIOCLINUX, subcode=TIOCL_SETVESABLANK
Handles the Power Saving feature of the new generation of monitors. VESA screen blanking mode is
set to argp[1], which governs what screen blanking does:
0 Screen blanking is disabled.
1 The current video adapter register settings are saved, then the controller is programmed to
turn off the vertical synchronization pulses. This puts the monitor into "standby" mode.
If your monitor has an Off_Mode timer, then it will eventually power down by itself.
2 The current settings are saved, then both the vertical and horizontal synchronization
pulses are turned off. This puts the monitor into "off" mode. If your monitor has no
Off_Mode timer, or if you want your monitor to power down immediately when the blank_timer
times out, then you choose this option. (Caution: Powering down frequently will damage the
monitor.) (Since Linux 1.1.76.)
TIOCLINUX, subcode=TIOCL_SETKMSGREDIRECT
Change target of kernel messages ("console"): by default, and if this is set to 0, messages are
written to the currently active VT. The VT to write to is a single byte following subcode.
(Since Linux 2.5.36.)
TIOCLINUX, subcode=TIOCL_GETFGCONSOLE
Returns the number of VT currently in foreground. (Since Linux 2.5.36.)
TIOCLINUX, subcode=TIOCL_SCROLLCONSOLE
Scroll the foreground VT by the specified amount of lines down, or half the screen if 0. lines is
*(((int32_t *)&subcode) + 1). (Since Linux 2.5.67.)
TIOCLINUX, subcode=TIOCL_BLANKSCREEN
Blank the foreground VT, ignoring "pokes" (typing): can only be unblanked explicitly (by switching
VTs, to text mode, etc.). (Since Linux 2.5.71.)
TIOCLINUX, subcode=TIOCL_BLANKEDSCREEN
Returns the number of VT currently blanked, 0 if none. (Since Linux 2.5.71.)
TIOCLINUX, subcode=16
Never used.
TIOCLINUX, subcode=TIOCL_GETKMSGREDIRECT
Returns target of kernel messages. (Since Linux 2.6.17.)
RETURN VALUE
On success, 0 is returned (except where indicated). On failure, -1 is returned, and errno is set to
indicate the error.
ERRORS
EBADF The file descriptor is invalid.
EINVAL The file descriptor or argp is invalid.
ENOTTY The file descriptor is not associated with a character special device, or the specified operation
does not apply to it.
EPERM Insufficient permission.
NOTES
Warning: Do not regard this man page as documentation of the Linux console ioctls. This is provided for
the curious only, as an alternative to reading the source. Ioctl's are undocumented Linux internals,
liable to be changed without warning. (And indeed, this page more or less describes the situation as of
kernel version 1.1.94; there are many minor and not-so-minor differences with earlier versions.)
Very often, ioctls are introduced for communication between the kernel and one particular well-known
program (fdisk, hdparm, setserial, tunelp, loadkeys, selection, setfont, etc.), and their behavior will
be changed when required by this particular program.
Programs using these ioctls will not be portable to other versions of UNIX, will not work on older
versions of Linux, and will not work on future versions of Linux.
Use POSIX functions.
SEE ALSO
dumpkeys(1), kbd_mode(1), loadkeys(1), mknod(1), setleds(1), setmetamode(1), execve(2), fcntl(2),
ioctl_tty(2), ioperm(2), termios(3), console_codes(4), mt(4), sd(4), tty(4), ttyS(4), vcs(4), vcsa(4),
charsets(7), mapscrn(8), resizecons(8), setfont(8)
/usr/include/linux/kd.h, /usr/include/linux/vt.h
Linux man-pages 6.7 2024-03-03 ioctl_console(2)