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IOCTL_CONSOLE(2) Linux Programmer's Manual IOCTL_CONSOLE(2)

ioctl_console - ioctls for console terminal and virtual consoles

The following Linux-specific ioctl(2) requests are supported for console terminals and virtual consoles. Each requires a third argument, assumed here to be argp.

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
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.

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.)
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.)
Get keyboard type. This returns the value KB_101, defined as 0x02.
Add I/O port as valid. Equivalent to ioperm(arg,1,1).
Delete I/O port as valid. Equivalent to ioperm(arg,1,0).
Enable I/O to video board. Equivalent to ioperm(0x3b4, 0x3df-0x3b4+1, 1).
Disable I/O to video board. Equivalent to ioperm(0x3b4, 0x3df-0x3b4+1, 0).
Set text/graphics mode. argp is an unsigned integer containing one of:
KD_TEXT 0x00
KD_GRAPHICS 0x01
Get text/graphics mode. argp points to an int which is set to one of the values shown above for KDSETMODE.
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.)
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.
Get the current default color map from kernel. argp points to a 48-byte array. (Since Linux 1.3.3.)
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.)
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.
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.)
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.
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.)
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.)
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.
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.)
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.
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.)
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.)
Put unicode-to-font mapping in kernel. argp points to a struct unimapdesc. (Since Linux 1.1.92)
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.)
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 */
Sets current keyboard mode. argp is a long equal to one of the values shown for KDGKBMODE.
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
Sets meta key handling mode. argp is a long equal to one of the values shown above for KDGKBMETA.
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.
Sets one entry in translation table. argp points to a struct kbentry.
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.
Sets one function key string entry. argp points to a struct kbsentry.
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;
};

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.)
Write kernel keycode table entry. argp points to a struct kbkeycode. (Since Linux 1.1.63.)
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.)
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).
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 req */


    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
Set mode of active vt. argp points to a struct vt_mode.
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. (Kernels 1.0 through 1.1.92.)
Release a display.
Switch to vt argp (1 <= argp <= MAX_NR_CONSOLES).
Wait until vt argp has been activated.
Deallocate the memory associated with vt argp. (Since Linux 1.1.54.)
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.)
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.

Dump the screen. Disappeared in Linux 1.1.92. (With kernel 1.1.92 or later, read from /dev/vcsN or /dev/vcsaN instead.)
Get task information. Disappeared in Linux 1.1.92.
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 the static array sel_buffer in devices/char/console.c.
Paste selection. The characters in the selection buffer are written to fd.
Unblank the screen.
Sets contents of a 256-bit look up table defining characters in a "word", for word-by-word selection. (Since Linux 1.1.32.)
argp points to a char which is set to the value of the kernel variable shift_state. (Since Linux 1.1.32.)
argp points to a char which is set to the value of the kernel variable report_mouse. (Since Linux 1.1.33.)
Dump screen width and height, cursor position, and all the character-attribute pairs. (Kernels 1.1.67 through 1.1.91 only. With kernel 1.1.92 or later, read from /dev/vcsa* instead.)
Restore screen width and height, cursor position, and all the character-attribute pairs. (Kernels 1.1.67 through 1.1.91 only. With kernel 1.1.92 or later, write to /dev/vcsa* instead.)
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.)

On success, 0 is returned. On error, -1 is returned, and errno is set.

errno may take on these values:

The file descriptor is invalid.
The file descriptor or argp is invalid.
The file descriptor is not associated with a character special device, or the specified request does not apply to it.
Insufficient permission.

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.

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

This page is part of release 5.10 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

2017-09-15 Linux