Reading Function Keys in bash

This page has not been peer-reviewed for correctness, usefulness, portability or style. Use at your own risk.

The initial response to this is mostly "why bother?". The answer is because it is more robust than simply using read. The main problem with directly calling read is that the escape sequences use digits and letter so if you use something like the following it can lead to unexpected consequences/behavior.

  while read -sN1 ; do
    echo "${REPLY}";
    case "${REPLY}" in
      A) echo 'either "A" or up arrow ';;
      B) echo 'either "B" or down arrow ';;
      1) echo 'either "1" or any function key ';;
    esac
  done

It's even worse than that because an escape sequence can look something like this.

  $'\e[1;12A'

So you can just not use the contentious keys "0123456789ABCDEPQRSZ;?+", but no guarantee that that's a full list.

A better solution is to use something like this where we delineate each key with a Enter/Return key press.

  while read  ; do
    echo "${REPLY}";
    case "${REPLY}" in
      A) echo 'Is A';;
      1) echo 'Is 1';;
    esac
  done

However that makes for a somewhat stilted interface.

Now we could also do something like this

  ReadKey() {
    # Wait for first char
    if read -sN1 _REPLY; then
      # Read rest of chars
      while read -sN1 -t 0.001 ; do
        _REPLY+="${REPLY}"
      done
    fi
  }
  while ReadKey  ; do
    echo "${_REPLY}";
    case "${_REPLY}" in
      A) echo 'Is A';;
      1) echo 'Is 1';;
      $'\e[A') echo 'Up Arrow';;
      $'\e[1;2A') echo 'Shift + Up Arrow';;
      $'\e[4~' | $'\e[4z') echo 'F4';;
      $'\e[4;2~' | $'\e[4;2z') echo 'Shift + F4';;
    esac
  done

Now the above example is ok if you don't want to require the user to press the enter key and you don't want to use function keys however using function keys in the above manner is a mess there can be something like 4 different escape sequences for a key depending on the emulation mode. Furthermore it is difficult to ignore modifier keys. Technically an escape sequence for an up arrow ignoring the modifier keys requires a regex like this

    # Requires extglob
    case "${_REPLY}" in
      $'\e['?(+([0-9);+([0-9))A) echo 'Up Arrow Ignoring Modifiers'
    esac

Though mostly this should do

    # no extglob
    case "${_REPLY}" in
      $'\e[A' | $'\e[1;'[2-9]A) echo 'Up Arrow Ignoring Modifiers'
    esac

The following example builds on the last example and allows a more intuitive usage of Function keys in bash. It abstracts the escape sequence messiness for these keys and as such allows for a more portable/intuitive solutions. As it understands about escape sequences it also protects the caller from the problems with the first example above. Furthermore as no sub shells are required it is quicker than calling an external program or function to read the key.

#set -o errexit
#set -o errtrace
set -o nounset


  if [ "${S8C1T:-0}" != "1" ] ; then
    declare -gr SS3=$'\eO'      # Single Shift Select of G3 Character Set ( SS3 is 0x8f): affects next character only
    declare -gr CSI=$'\e['      # Control Sequence Introducer ( CSI is 0x9b)
  else
    declare -gr SS3=$'\x8f'     # Single Shift Select of G3 Character Set ( SS3 is 0x8f): affects next character only
    declare -gr CSI=$'\x9b'     # Control Sequence Introducer ( CSI is 0x9b)
  fi


  vt100_DECRST() {
    IFS=';' eval 'echo -n "${CSI}?${*?Missing Pm}l"'
  }
  vt100_DECSET() {
    IFS=';' eval 'echo -n "${CSI}?${*?Missing Pm}h"'
  }
  mouse_type=(
        [0]=9     ## X10 mouse reporting, for compatibility with X10's xterm, reports on button press.
        [1]=1000  ## X11 mouse reporting, reports on button press and release.
        [2]=1001  ## highlight reporting, useful for reporting mouse highlights
        [3]=1002  ## button movement reporting, reports movement when a button is presse
        [4]=1003  ## all movement reporting, reports all movements.
        [5]=1004  ## FocusIn/FocusOut can be combined with any of the mouse events since it uses a different protocol. When set, it causes xterm to send CSI I when the terminal gains focus, and CSI O when it loses focus.
        [6]=1005  ## Extended mouse mode enables UTF-8 encoding for C x and C y under all tracking modes, expanding the maximum encodable position from 223 to 2015. For positions less than 95, the resulting output is identical under both modes. Under extended mouse mode, positions greater than 95 generate "extra" bytes which will confuse applications which do not treat their input as a UTF-8 stream. Likewise, C b will be UTF-8 encoded, to reduce confusion with wheel mouse events.
    )

  ord() {
    printf -v "${1?Missing Dest Variable}" "${3:-%d}" "'${2?Missing Char}"
  }
  ord_eascii() {
    LC_CTYPE=C ord "${@}"
  }
  AdjustMousePos() {
    local -i _INDEX
    ord_eascii _INDEX "${2}"
    eval ${1}'=$(( ${_INDEX}-32))'
  }

  ###############################
  ##
  ##    READ KEY CRAP
  ##
  ##
  ###############################
  KeyModifiers=(
             [2]="S"   [3]="A"   [4]="AS"   [5]="C"   [6]="CS"  [7]="CA"    [8]="CAS"
    [9]="M" [10]="MS" [11]="MA" [12]="MAS" [13]="MC" [14]="MCS" [15]="MCA" [16]="MCAS"
    )
  KeybFntKeys=(
    [1]="home" [2]="insert" [3]="delete"  [4]="end"   [5]="pageUp" [6]="pageDown"
    [11]="f1"  [12]="f2"    [13]="f3"     [14]="f4"   [15]="f5"
    [17]="f6"  [18]="f7"    [19]="f8"     [20]="f9"   [21]="f10"
    [23]="f11" [24]="f12"   [25]="f13"    [26]="f14"  [28]="f15"
    [29]="f16" [31]="f17"   [32]="f18"    [33]="f19"  [34]="f20"
    )
  SunKeybFntKeys=(
    [214]="home"  [2]="insert" [3]="delete" [4]="end"   [216]="pageUp" [222]="pageDown"
    [224]="f1"  [225]="f2"    [226]="f3"    [227]="f4"  [228]="f5"
    [229]="f6"  [230]="f7"    [231]="f8"    [232]="f9"  [233]="f10"
    [192]="f11" [193]="f12"   [218]="keypad-five" [220]="keypad-delete"
    )
  KeybFntKeysAlt=(
    # A          B              C               D             E                   F             H
    [0x41]="up" [0x42]="down" [0x43]="right" [0x44]="left" [0x45]="keypad-five" [0x46]="end" [0x48]="home"
    # I               O
    [0x49]="InFocus" [0x4f]="OutOfFocus"
    # P           Q           R           S             Z
    [0x50]="f1" [0x51]="f2" [0x52]="f3" [0x53]="f4"  [0x5a]="S-HT"
    )
  C0CtrlChars=(
    [0x00]="Null" [0x01]="SOH" [0x02]="STX" [0x03]="ETX" [0x04]="EOT" [0x05]="ENQ" [0x06]="ACK"
    [0x07]="BEL"  [0x08]="BS"  [0x09]="HT"  [0x0A]="LF"  [0x0B]="VT"  [0x0C]="FF"  [0x0D]="CR"
    [0x0E]="SO"   [0x0F]="SI"  [0x10]="DLE" [0x11]="DC1" [0x12]="DC2" [0x13]="DC3" [0x14]="DC4"
    [0x15]="NAK"  [0x16]="SYN" [0x17]="ETB" [0x18]="CAN" [0x19]="EM"  [0x1A]="SUB" [0x1B]="ESC"
    [0x1C]="FS"   [0x1D]="GS"  [0x1E]="RS"  [0x1F]="US"  [0x20]="SP"  [0x7F]="DEL"
  )
  C0CtrlCharsAlt=(
    [0x01]="C-A" [0x02]="C-B" [0x03]="C-C" [0x04]="C-D" [0x05]="C-E" [0x06]="C-F" [0x07]="C-G"
    [0x08]="C-H" [0x09]="C-I" [0x0a]="C-J" [0x0b]="C-K" [0x0c]="C-L" [0x0d]="C-M" [0x0e]="C-N"
    [0x0f]="C-O" [0x10]="C-P" [0x11]="C-Q" [0x12]="C-R" [0x13]="C-S" [0x14]="C-T" [0x15]="C-U"
    [0x16]="C-V" [0x17]="C-W" [0x18]="C-X" [0x19]="C-Y" [0x1a]="C-Z" [0x1b]="C-[" [0x1c]="C-]"
    [0x1d]="C-}" [0x1e]="C-^" [0x1f]="C-_" [0x20]="C-SP"  [0x7F]="DEL"
  )
  C1CtrlCharsEsc=(
    [0x40]="PAD"  [0x41]="HOP"  [0x42]="BPH" [0x43]="NBH"
    [0x44]="IND"  [0x45]="NEL"  [0x46]="SSA" [0x47]="ESA"
    [0x48]="HTS"  [0x49]="HTJ"  [0x4A]="VTS" [0x4B]="PLD"
    [0x4C]="PLU"  [0x4D]="RI"   [0x4E]="SS2" [0x4F]="SS3"
    [0x50]="DCS"  [0x51]="PU1"  [0x52]="PU2" [0x53]="STS"
    [0x54]="CCH"  [0x55]="MW"   [0x56]="SPA" [0x57]="EPA"
    [0x58]="SOS"  [0x59]="SGCI" [0x5A]="SCI" [0x5B]="CSI"
    [0x5C]="ST"   [0x5D]="OSC"  [0x5E]="PM"  [0x5F]="APC"
  )
  C1CtrlChars=(
    [0x80]="PAD"  [0x81]="HOP"  [0x82]="BPH" [0x83]="NBH"
    [0x84]="IND"  [0x85]="NEL"  [0x86]="SSA" [0x87]="ESA"
    [0x88]="HTS"  [0x89]="HTJ"  [0x8A]="VTS" [0x8B]="PLD"
    [0x8C]="PLU"  [0x8D]="RI"   [0x8E]="SS2" [0x8F]="SS3"
    [0x90]="DCS"  [0x91]="PU1"  [0x92]="PU2" [0x93]="STS"
    [0x94]="CCH"  [0x95]="MW"   [0x96]="SPA" [0x97]="EPA"
    [0x98]="SOS"  [0x99]="SGCI" [0x9A]="SCI" [0x9B]="CSI"
    [0x9C]="ST"   [0x9D]="OSC"  [0x9E]="PM"  [0x9F]="APC"
  )
  C1CtrlCharsAlt=(
    [0x01]="CA-A" [0x02]="CA-B" [0x03]="CA-C" [0x04]="CA-D"  [0x05]="CA-E" [0x06]="CA-F" [0x07]="CA-G"
    [0x08]="CA-H" [0x09]="CA-I" [0x0a]="CA-J" [0x0b]="CA-K"  [0x0c]="CA-L" [0x0d]="CA-M" [0x0e]="CA-N"
    [0x0f]="CA-O" [0x10]="CA-P" [0x11]="CA-Q" [0x12]="CA-R"  [0x13]="CA-S" [0x14]="CA-T" [0x15]="CA-U"
    [0x16]="CA-V" [0x17]="CA-W" [0x18]="CA-X" [0x19]="CA-Y"  [0x1a]="CA-Z" [0x1b]="CA-[" [0x1c]="CA-]"
    [0x1d]="CA-}" [0x1e]="CA-^" [0x1f]="CA-_" [0x20]="CA-SP" [0x7F]="A-DEL"
  )
  MouseButtons=(
    [0x00]="MB1-P" [0x01]="MB2-P" [0x02]="MB3-P" [0x03]="MB-R"
    [0x20]="MB1-M" [0x21]="MB2-M" [0x22]="MB3-M" [0x23]="MB-M"
    [0x40]="MB4-P" [0x41]="MB5-P"
  )
  MouseMetaButtons=(
    [0x04]="S-"    [0x08]="A-"    [0x0c]="AS-"
    [0x10]="C-"    [0x14]="CS-"   [0x1c]="CAS-"
  )
  GetMouseButton() {
    local MouseBtn
    AdjustMousePos MouseBtn "${2}"
    MouseBtn="${MouseMetaButtons[$(( ${MouseBtn} & 0x1C))]-}${MouseButtons[$(( ${MouseBtn} & 0xe3))]}"
    eval ${1}='"${MouseBtn}"'
  }
  mouse_on="$(vt100_DECSET ${mouse_type[1]})"
  mouse_off="$(vt100_DECRST "${mouse_type[1]}" )"


  ReadKey() {
    unset UInput[@]
    local escapeSequence
    local REPLY

    echo -n "${mouse_on}"
    if IFS='' read  -srN1 ${1:-} escapeSequence; then
      case "${escapeSequence}" in
        [^[:cntrl:]])
          UInput[0]="${escapeSequence}"
          ;;
        $'\e')
          while IFS='' read -srN1 -t0.0001 ; do
            escapeSequence+="${REPLY}"
          done
          case "${escapeSequence}" in
              $'\e'[^[:cntrl:]]) echo -n "A-${escapeSequence:1}" ;;
              ${CSI}t)
                UInput[0]="MouseTrack"
                AdjustMousePos UInput[1] "${escapeSequence:3:1}"
                AdjustMousePos UInput[2] "${escapeSequence:4:1}"
                ;;
              ${CSI}T)
                UInput[0]="MouseTrack"
                AdjustMousePos UInput[1] "${escapeSequence:3:1}"
                AdjustMousePos UInput[2] "${escapeSequence:4:1}"
                AdjustMousePos UInput[3] "${escapeSequence:5:1}"
                AdjustMousePos UInput[4] "${escapeSequence:6:1}"
                AdjustMousePos UInput[5] "${escapeSequence:7:1}"
                AdjustMousePos UInput[6] "${escapeSequence:8:1}"
                ;;
              ${CSI}M*)
                GetMouseButton UInput[0] "${escapeSequence:3:1}"
                if [ -n "${UInput[0]}" ]; then
                  AdjustMousePos UInput[1] "${escapeSequence:4:1}"
                  AdjustMousePos UInput[2] "${escapeSequence:5:1}"
                else
                  UInput[0]=$(printf 'Mouse-\\x%02x %q'  "'${escapeSequence:3:1}" "${escapeSequence:4}")
                fi
                ;;
              ${CSI}[0-9]*[ABCDEFHIOZPQRSz~])
                local CSI_Params=( ${escapeSequence//[!0-9]/ } )
                local CSI_Func="${escapeSequence:${#escapeSequence}-1}"
                case "${CSI_Func}" in
                  z) # Sun Function Keys
                    UInput[0]="${SunKeybFntKeys[${CSI_Params[0]}]-}"
                    if [ -n "${UInput[0]}" ]; then
                      [ ${#CSI_Params[@]} -le 1 ] ||  UInput[0]="${KeyModifiers[${CSI_Params[1]}]}-${UInput[0]}"
                    else
                      UInput[0]="CSI ${CSI_Params[*]} ${CSI_Func}"
                    fi
                    ;;
                  '~') # Function Keys
                    UInput[0]="${KeybFntKeys[${CSI_Params[0]}]-}"
                    if [ -n "${UInput[0]}" ]; then
                      [ ${#CSI_Params[@]} -le 1 ] ||  UInput[0]="${KeyModifiers[${CSI_Params[1]}]}-${UInput[0]}"
                    else
                      UInput[0]="CSI ${CSI_Params[*]} ${CSI_Func}"
                    fi
                    ;;
                  A|B|C|D|E|F|H|I|O|Z|P|Q|R|S)
                    ord_eascii CSI_Func "${CSI_Func}"
                    UInput[0]="${KeybFntKeysAlt[${CSI_Func}]}"
                    if [ -n "${UInput[0]}" ]; then
                      [ ${#CSI_Params[@]} -le 1 ] ||  UInput[0]="${KeyModifiers[${CSI_Params[1]}]}-${UInput[0]}"
                    else
                      UInput[0]="CSI ${CSI_Params[*]} ${CSI_Func}"
                    fi
                    ;;
                  *)
                    UInput[0]="CSI ${CSI_Params[*]} ${CSI_Func}"
                    ;;
                esac
                ;;
              ${SS3}*[ABCDEFHPQRSIO~])
                local SS3_Params=( ${escapeSequence//[!0-9]/ } )
                local SS3_Func="${escapeSequence:${#escapeSequence}-1}"
                case "${SS3_Func}" in
                  A|B|C|D|E|F|H|P|Q|R|S|~)
                    ord_eascii SS3_Func "${SS3_Func}"
                    UInput[0]="${KeybFntKeysAlt[${SS3_Func}]-}"
                    if [ -n "${UInput[0]}" ]; then
                      [ ${#SS3_Params[@]} -lt 1 ] ||  UInput[0]="${KeyModifiers[${SS3_Params[0]}]}-${UInput[0]}"
                    else
                      UInput[0]="SS3 ${SS3_Params[*]-} ${SS3_Func}"
                    fi
                    ;;
                  *)
                    UInput[0]="SS3 ${SS3_Params[*]-} ${SS3_Func}"
                    ;;
                esac
                ;;
              $'\e'[[:cntrl:]])
                ord_eascii UInput[0] "${escapeSequence:1:1}"
                UInput[0]="${C1CtrlCharsAlt[${UInput[0]}]:-}"
                [ -n "${UInput[0]:-}" ] ||  UInput[0]="$(printf "%q" "${escapeSequence}")"
                ;;
              $'\e') UInput[0]="ESC" ;;
              *)
                UInput[0]="$(printf "%q" "${escapeSequence}")"
                ;;
          esac
          ;;
        *)
          ord_eascii UInput[0] "${escapeSequence}"
          UInput[0]="${C0CtrlChars[${UInput[0]}]:-}"
          [ -n "${UInput[0]:-}" ] ||  UInput[0]="$(printf '%q' "'${escapeSequence}")"
          ;;
      esac
    fi
    echo -n "${mouse_off}"
  }

• The ReadKey function can then be called in this manor.

•   HandleKey() {
      local -a UInput
      while true; do
        if ReadKey ; then
          case "${UInput[0]:-}" in
            CR|NULL|LF|q)
              echo "\"${UInput[*]-}\""
              break
              ;;
            *up)       echo "Up Arrow ignoring modifier keys"  ;;
            down)      echo "Down Arrow No modifier keys"      ;;
            S-down)    echo "Shift + Down Arrow"               ;;
            A-down)    echo "Alt + Down Arrow"                 ;;
            AS-down)   echo "Alt + Shift + Down Arrow"         ;;
            C-down)    echo "Control + Down Arrow"             ;;
            CS-down)   echo "Control + Shift + Down Arrow"      ;;
            CA-down)   echo "Control + Alt + Down Arrow"        ;;
            CAS-down)  echo "Control + Alt + Shift + Down Arrow";;
            MCAS-down) echo "Meta + Control + Alt + Shift + Down Arrow";;
            *)
              echo "\"${UInput[*]-}\""
              ;;
          esac
        fi
      done
    }
  HandleKey

The main problem with the previous example is that like most such bash implementations it requires a break between function keys. Now in a user interface this is not a problem because there is always a minimal delay between key presses. However on slower systems it could happen that 2 key preses get evaluated together, the only downside is that in those rare cases the keys get ignored. But this also means that it can't be used with buffered function key sequences.

vt100 Parser Example

A more complex solution using a full vt100 parser. This following solution fixes the problems of the previous example as it doesn't blindly gobble up the entire buffer but instead intelligently reads the key sequence. The downside is that it is quite a bit more complex, and takes about 0.005s per function key instead of 0.001 sec.

declare -gri VTPARSE_ACTION_CLEAR="1"
declare -gri VTPARSE_ACTION_COLLECT="2"
declare -gri VTPARSE_ACTION_CSI_DISPATCH="3"
declare -gri VTPARSE_ACTION_ESC_DISPATCH="4"
declare -gri VTPARSE_ACTION_ESC_EXECUTE="5"
declare -gri VTPARSE_ACTION_EXECUTE="6"
declare -gri VTPARSE_ACTION_HOOK="7"
declare -gri VTPARSE_ACTION_IGNORE="8"
declare -gri VTPARSE_ACTION_OSC_END="9"
declare -gri VTPARSE_ACTION_OSC_PUT="10"
declare -gri VTPARSE_ACTION_OSC_START="11"
declare -gri VTPARSE_ACTION_PARAM="12"
declare -gri VTPARSE_ACTION_PRINT="13"
declare -gri VTPARSE_ACTION_PUT="14"
declare -gri VTPARSE_ACTION_SS2_DISPATCH="15"
declare -gri VTPARSE_ACTION_SS3_DISPATCH="16"
declare -gri VTPARSE_ACTION_UNHOOK="17"

declare -gra VTPARSE_ACTION_NAMES=(
   [0 ]="<no action>"
   [${VTPARSE_ACTION_CLEAR}]="CLEAR"
   [${VTPARSE_ACTION_COLLECT}]="COLLECT"
   [${VTPARSE_ACTION_CSI_DISPATCH}]="CSI_DISPATCH"
   [${VTPARSE_ACTION_ESC_DISPATCH}]="ESC_DISPATCH"
   [${VTPARSE_ACTION_ESC_EXECUTE}]="ESC_EXECUTE"
   [${VTPARSE_ACTION_EXECUTE}]="EXECUTE"
   [${VTPARSE_ACTION_HOOK}]="HOOK"
   [${VTPARSE_ACTION_IGNORE}]="IGNORE"
   [${VTPARSE_ACTION_OSC_END}]="OSC_END"
   [${VTPARSE_ACTION_OSC_PUT}]="OSC_PUT"
   [${VTPARSE_ACTION_OSC_START}]="OSC_START"
   [${VTPARSE_ACTION_PARAM}]="PARAM"
   [${VTPARSE_ACTION_PRINT}]="PRINT"
   [${VTPARSE_ACTION_PUT}]="PUT"
   [${VTPARSE_ACTION_SS2_DISPATCH}]="SS2_DISPATCH"
   [${VTPARSE_ACTION_SS3_DISPATCH}]="SS3_DISPATCH"
   [${VTPARSE_ACTION_UNHOOK}]="UNHOOK"
)
declare -gri VTPARSE_STATE_ANYWHERE="0"
declare -gri VTPARSE_STATE_CSI_ENTRY="1"
declare -gri VTPARSE_STATE_CSI_IGNORE="2"
declare -gri VTPARSE_STATE_CSI_INTERMEDIATE="3"
declare -gri VTPARSE_STATE_CSI_PARAM="4"
declare -gri VTPARSE_STATE_DCS_ENTRY="5"
declare -gri VTPARSE_STATE_DCS_IGNORE="6"
declare -gri VTPARSE_STATE_DCS_INTERMEDIATE="7"
declare -gri VTPARSE_STATE_DCS_PARAM="8"
declare -gri VTPARSE_STATE_DCS_PASSTHROUGH="9"
declare -gri VTPARSE_STATE_ESCAPE="10"
declare -gri VTPARSE_STATE_ESCAPE_INTERMEDIATE="11"
declare -gri VTPARSE_STATE_GROUND="12"
declare -gri VTPARSE_STATE_OSC_STRING="13"
declare -gri VTPARSE_STATE_SOS_PM_APC_STRING="14"
declare -gri VTPARSE_STATE_SS2_ENTRY="15"
declare -gri VTPARSE_STATE_SS3_ENTRY="16"
declare -gri VTPARSE_STATE_SS3_PARAM="17"

declare -gra VTPARSE_STATE_NAMES=(
   [${VTPARSE_STATE_ANYWHERE}]="ANYWHERE"
   [${VTPARSE_STATE_CSI_ENTRY}]="CSI_ENTRY"
   [${VTPARSE_STATE_CSI_IGNORE}]="CSI_IGNORE"
   [${VTPARSE_STATE_CSI_INTERMEDIATE}]="CSI_INTERMEDIATE"
   [${VTPARSE_STATE_CSI_PARAM}]="CSI_PARAM"
   [${VTPARSE_STATE_DCS_ENTRY}]="DCS_ENTRY"
   [${VTPARSE_STATE_DCS_IGNORE}]="DCS_IGNORE"
   [${VTPARSE_STATE_DCS_INTERMEDIATE}]="DCS_INTERMEDIATE"
   [${VTPARSE_STATE_DCS_PARAM}]="DCS_PARAM"
   [${VTPARSE_STATE_DCS_PASSTHROUGH}]="DCS_PASSTHROUGH"
   [${VTPARSE_STATE_ESCAPE}]="ESCAPE"
   [${VTPARSE_STATE_ESCAPE_INTERMEDIATE}]="ESCAPE_INTERMEDIATE"
   [${VTPARSE_STATE_GROUND}]="GROUND"
   [${VTPARSE_STATE_OSC_STRING}]="OSC_STRING"
   [${VTPARSE_STATE_SOS_PM_APC_STRING}]="SOS_PM_APC_STRING"
   [${VTPARSE_STATE_SS2_ENTRY}]="SS2_ENTRY"
   [${VTPARSE_STATE_SS3_ENTRY}]="SS3_ENTRY"
   [${VTPARSE_STATE_SS3_PARAM}]="SS3_PARAM"
)
declare -gra VTPARSE_STATE_TABLE=(
  [${VTPARSE_STATE_ANYWHERE}]="0000000000000000000000000000000000000000000000006c006c0a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006c6c6c6c6c6c6c6c6c6c6c6c6c6c0f6c056c6c6c6c6c6c6c0e6c6c016c0d0e0e"
  [${VTPARSE_STATE_CSI_ENTRY}]="606060606060606060606060606060606060606060606060006000006060606023232323232323232323232323232323c4c4c4c4c4c4c4c4c4c402c4242424243c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c80"
  [${VTPARSE_STATE_CSI_IGNORE}]="606060606060606060606060606060606060606060606060006000006060606080808080808080808080808080808080808080808080808080808080808080800c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c80"
  [${VTPARSE_STATE_CSI_INTERMEDIATE}]="606060606060606060606060606060606060606060606060006000006060606020202020202020202020202020202020020202020202020202020202020202023c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c80"
  [${VTPARSE_STATE_CSI_PARAM}]="606060606060606060606060606060606060606060606060006000006060606023232323232323232323232323232323c0c0c0c0c0c0c0c0c0c002c0020202023c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c3c80"
  [${VTPARSE_STATE_DCS_ENTRY}]="808080808080808080808080808080808080808080808080008000008080808027272727272727272727272727272727c8c8c8c8c8c8c8c8c8c806c82828282809090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090980"
  [${VTPARSE_STATE_DCS_IGNORE}]="8080808080808080808080808080808080808080808080800080000080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080000000000000000000000000000000000000000000000000000000000c"
  [${VTPARSE_STATE_DCS_INTERMEDIATE}]="8080808080808080808080808080808080808080808080800080000080808080202020202020202020202020202020200606060606060606060606060606060609090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090980"
  [${VTPARSE_STATE_DCS_PARAM}]="808080808080808080808080808080808080808080808080008000008080808027272727272727272727272727272727c0c0c0c0c0c0c0c0c0c006c00606060609090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090909090980"
  [${VTPARSE_STATE_DCS_PASSTHROUGH}]="e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e000e00000e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e0e080000000000000000000000000000000000000000000000000000000000c"
  [${VTPARSE_STATE_ESCAPE}]="50505050505050505050505050505050505050505050505000500000505050502b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c0f0g054c4c4c4c4c4c4c0e4c4c014c0d0e0e4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c5c"
  [${VTPARSE_STATE_ESCAPE_INTERMEDIATE}]="6060606060606060606060606060606060606060606060600060000060606060202020202020202020202020202020204c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c4c80"
  [${VTPARSE_STATE_GROUND}]="6060606060606060606060606060606060606060606060600060000060606060d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d06060606060606060606060606060606000606060606060606060600060"
  [${VTPARSE_STATE_OSC_STRING}]="8080808080808080808080808080808080808080808080800080000080808080a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0a0000000000000000000000000000000000000000000000000000000000c"
  [${VTPARSE_STATE_SOS_PM_APC_STRING}]="8080808080808080808080808080808080808080808080800080000080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080808080000000000000000000000000000000000000000000000000000000000c"
  [${VTPARSE_STATE_SS2_ENTRY}]="60606060606060606060606060606060606060606060606000600000606060600000000000000000000000000000000000000000000000000000000000000000fcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcfc80"
  [${VTPARSE_STATE_SS3_ENTRY}]="606060606060606060606060606060606060606060606060006000006060606000000000000000000000000000000000chchchchchchchchchch000000000000gcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgc80"
  [${VTPARSE_STATE_SS3_PARAM}]="606060606060606060606060606060606060606060606060006000006060606000000000000000000000000000000000c0c0c0c0c0c0c0c0c0c0000000000000gcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgcgc80"
)

declare -gr VTPARSE_BASE="0123456789abcdefghijklmnopqrstuvwxyz"
declare -gr VTPARSE_ENTRY_ACTIONS="0100010007100b0110"

declare -gr VTPARSE_EXIT_ACTIONS="000000000h00090000"

  ord() {
    printf -v "${1?Missing Dest Variable}" "${3:-%d}" "'${2?Missing Char}"
  }
  ord_eascii() {
    LC_CTYPE=C ord "${@}"
  }
  substr() {
      local idx
      typeset -gi _INDEX
      case "${1}" in
        *${2}*)
            idx="${1%"${2}"*}";
            _INDEX=${#idx}
        ;;
          *)
            _INDEX=0
        ;;
      esac
  }




  declare -gr  MAX_INTERMEDIATE_CHARS=2

  declare -gi  vtparser_state
  declare -g   vtparser_intermediate_chars
  declare -ga  vtparser_params
  declare -gi  vtparser_ignore_flagged
  declare -g   vtparser_cb
  declare -g   vtparser_read


  vtparse_init() {
    vtparser_state="${VTPARSE_STATE_GROUND}"
    vtparser_intermediate_chars=""
    vtparser_params=( )
    vtparser_ignore_flagged=0
    vtparser_cb=${1?Missing Callback Function}
    vtparser_read=${2?Missing Read Function}
  }
  nop() {
    echo -n ""
  }
  do_action() {
    # Some actions we handle internally (like parsing parameters), others
    # we hand to our client for processing
    case "${1}" in
      ${VTPARSE_ACTION_ESC_EXECUTE}|${VTPARSE_ACTION_PRINT}|${VTPARSE_ACTION_EXECUTE}|${VTPARSE_ACTION_HOOK}|${VTPARSE_ACTION_PUT}|${VTPARSE_ACTION_OSC_START}|${VTPARSE_ACTION_OSC_PUT}|${VTPARSE_ACTION_OSC_END}|${VTPARSE_ACTION_UNHOOK}|${VTPARSE_ACTION_CSI_DISPATCH}|${VTPARSE_ACTION_ESC_DISPATCH}|${VTPARSE_STATE_SS2_ENTRY}|${VTPARSE_STATE_SS3_ENTRY})
        ${vtparser_cb} "${@}" || return $?
        ;;
      ${VTPARSE_ACTION_IGNORE})
        nop
        ;;
      ${VTPARSE_ACTION_COLLECT})
        if [ ${#vtparser_intermediate_chars} -ge ${MAX_INTERMEDIATE_CHARS} ]; then
            vtparser_ignore_flagged=1
        else
            vtparser_intermediate_chars+="${2}";
        fi
        ;;
      ${VTPARSE_ACTION_PARAM})
        # process the param character
        if [ "${2}" = ";" ]; then
            vtparser_params[${#vtparser_params[@]}]="";
        else
            # the character is a digit
            if [ ${#vtparser_params[@]} -eq 0 ]; then
                vtparser_params[0]=""
            fi
            vtparser_params[${#vtparser_params[@]}-1]+="${2}"
        fi
        ;;
      ${VTPARSE_ACTION_CLEAR})
        vtparser_intermediate_chars=""
        vtparser_params=( )
        vtparser_ignore_flagged=0
        ;;
      *)
        echo "Unknown action ${1}"
        ;;

    esac
    return 0
  }
  vtparse_conv_base() {
    local _INDEX
    substr "${VTPARSE_BASE}" "${2:0:1}"
    eval ${1}'="${_INDEX}"'
  }
  do_state_change() {
    # A state change is an action and/or a new state to transition to.
    local -i action
    local -i new_state
    local -i RValue=0

    vtparse_conv_base action "${1:0:1}"
    vtparse_conv_base new_state "${1:1:1}"
    #printf "action=%s new_state=%s vtparser_state=%s change=%s\n" "${action}"  "${new_state}"  "${vtparser_state}"  "${1}"

    if [ "${new_state:=0}" != "0" ]; then
        # Perform up to three actions:
        #   1. the exit action of the old state
        #   2. the action associated with the transition
        #   3. the entry actionk of the new action
        local -i exit_action
        local -i entry_action
        vtparse_conv_base exit_action  "${VTPARSE_EXIT_ACTIONS:${vtparser_state}:1}"
        vtparse_conv_base entry_action "${VTPARSE_ENTRY_ACTIONS:${new_state}:1}"
        [ "${exit_action}" = "0" ]  ||  do_action "${exit_action}" $'\x00' 0
        [ "${action}" = "0" ]       ||  do_action "${action}" "${2}" "${3}" || RValue=$?
        [ "${entry_action}" = "0" ] ||  do_action "${entry_action}" $'\x00' 0
        vtparser_state=${new_state}
        return ${RValue}
    else
        [ "${action}" = "0" ]       ||  do_action "${action}" "${2}" "${3}" || return $?
    fi
  }

  vtparse() {
      local -i _INDEX
      local REPLY
      while ${vtparser_read} 1 ; do
          ord_eascii _INDEX "${REPLY:0:1}"

          # If a transition is defined from the "anywhere" state, always
          # use that.  Otherwise use the transition from the current state.

          _INDEX=${_INDEX}*2  # 2 characters per entry
          local change="${VTPARSE_STATE_TABLE[${VTPARSE_STATE_ANYWHERE}]:${_INDEX}:2}"
          [ "${change:-00}" != "00" ] || change="${VTPARSE_STATE_TABLE[${vtparser_state}]:${_INDEX}:2}"
          _INDEX=${_INDEX}/2

          do_state_change "${change}" "${REPLY}" "${_INDEX}" || break
      done
  }
  vtparse_read_stdin() {
    read -srN${1:-1} -d '' "${@:2}"
  }
  declare -g vtparse_read_buffer
  vtparse_read_buffer() {
    REPLY="${vtparse_read_buffer:0:${1:-1}}"
    vtparse_read_buffer="${vtparse_read_buffer:${1}}"
    [ ${#REPLY} -eq ${1} ] || return $?
  }


  vtparser_callback_debug() {
    local CArg
    printf "Received action %s, char=0x%02x char=%q\n" "${VTPARSE_ACTION_NAMES[${1}]}" "'${2}" "${2}"
    printf "Intermediate chars: '%s'\n" "${vtparser_intermediate_chars}"
    printf "%d Parameters:\n"  ${#vtparser_params[@]}
    for CArg in "${vtparser_params[@]-}"; do
        printf "\t%d\n" "${CArg}"
    done
    printf "\n"
  }
  ###############################
  ##
  ##    READ KEY CRAP
  ##
  ##
  ###############################
  KeyModifiers=(
    [1]=""  [2]="S-"   [3]="A-"   [4]="AS-"   [5]="C-"   [6]="CS-"  [7]="CA-"    [8]="CAS-"
    [9]="M-" [10]="MS-" [11]="MA-" [12]="MAS-" [13]="MC-" [14]="MCS-" [15]="MCA-" [16]="MCAS-"
    )
  KeybFntKeys=(
    [1]="home" [2]="insert" [3]="delete"  [4]="end"   [5]="pageUp" [6]="pageDown"
    [11]="f1"  [12]="f2"    [13]="f3"     [14]="f4"   [15]="f5"
    [17]="f6"  [18]="f7"    [19]="f8"     [20]="f9"   [21]="f10"
    [23]="f11" [24]="f12"   [25]="f13"    [26]="f14"  [28]="f15"
    [29]="f16" [31]="f17"   [32]="f18"    [33]="f19"  [34]="f20"
    )
  SunKeybFntKeys=(
    [214]="home"  [2]="insert" [3]="delete" [4]="end"   [216]="pageUp" [222]="pageDown"
    [224]="f1"  [225]="f2"    [226]="f3"    [227]="f4"  [228]="f5"
    [229]="f6"  [230]="f7"    [231]="f8"    [232]="f9"  [233]="f10"
    [192]="f11" [193]="f12"   [218]="keypad-five" [220]="keypad-delete"
    )
  KeybFntKeysAlt=(
    # A          B              C               D             E                   F             H
    [0x41]="up" [0x42]="down" [0x43]="right" [0x44]="left" [0x45]="keypad-five" [0x46]="end" [0x48]="home"
    # I               O
    [0x49]="InFocus" [0x4f]="OutOfFocus"
    # P           Q           R           S             Z
    [0x50]="f1" [0x51]="f2" [0x52]="f3" [0x53]="f4"  [0x5a]="S-HT"
    )
  C0CtrlChars=(
    [0x00]="Null" [0x01]="SOH" [0x02]="STX" [0x03]="ETX" [0x04]="EOT" [0x05]="ENQ" [0x06]="ACK"
    [0x07]="BEL"  [0x08]="BS"  [0x09]="HT"  [0x0A]="LF"  [0x0B]="VT"  [0x0C]="FF"  [0x0D]="CR"
    [0x0E]="SO"   [0x0F]="SI"  [0x10]="DLE" [0x11]="DC1" [0x12]="DC2" [0x13]="DC3" [0x14]="DC4"
    [0x15]="NAK"  [0x16]="SYN" [0x17]="ETB" [0x18]="CAN" [0x19]="EM"  [0x1A]="SUB" [0x1B]="ESC"
    [0x1C]="FS"   [0x1D]="GS"  [0x1E]="RS"  [0x1F]="US"  [0x20]="SP"  [0x7F]="DEL"
  )
  C0CtrlCharsAlt=(
    [0x01]="C-A" [0x02]="C-B" [0x03]="C-C" [0x04]="C-D" [0x05]="C-E" [0x06]="C-F" [0x07]="C-G"
    [0x08]="C-H" [0x09]="C-I" [0x0a]="C-J" [0x0b]="C-K" [0x0c]="C-L" [0x0d]="C-M" [0x0e]="C-N"
    [0x0f]="C-O" [0x10]="C-P" [0x11]="C-Q" [0x12]="C-R" [0x13]="C-S" [0x14]="C-T" [0x15]="C-U"
    [0x16]="C-V" [0x17]="C-W" [0x18]="C-X" [0x19]="C-Y" [0x1a]="C-Z" [0x1b]="C-[" [0x1c]="C-]"
    [0x1d]="C-}" [0x1e]="C-^" [0x1f]="C-_" [0x20]="C-SP"  [0x7F]="DEL"
  )

  C1CtrlCharsEsc=(
    [0x40]="PAD"  [0x41]="HOP"  [0x42]="BPH" [0x43]="NBH"
    [0x44]="IND"  [0x45]="NEL"  [0x46]="SSA" [0x47]="ESA"
    [0x48]="HTS"  [0x49]="HTJ"  [0x4A]="VTS" [0x4B]="PLD"
    [0x4C]="PLU"  [0x4D]="RI"   [0x4E]="SS2" [0x4F]="SS3"
    [0x50]="DCS"  [0x51]="PU1"  [0x52]="PU2" [0x53]="STS"
    [0x54]="CCH"  [0x55]="MW"   [0x56]="SPA" [0x57]="EPA"
    [0x58]="SOS"  [0x59]="SGCI" [0x5A]="SCI" [0x5B]="CSI"
    [0x5C]="ST"   [0x5D]="OSC"  [0x5E]="PM"  [0x5F]="APC"
  )
  C1CtrlChars=(
    [0x80]="PAD"  [0x81]="HOP"  [0x82]="BPH" [0x83]="NBH"
    [0x84]="IND"  [0x85]="NEL"  [0x86]="SSA" [0x87]="ESA"
    [0x88]="HTS"  [0x89]="HTJ"  [0x8A]="VTS" [0x8B]="PLD"
    [0x8C]="PLU"  [0x8D]="RI"   [0x8E]="SS2" [0x8F]="SS3"
    [0x90]="DCS"  [0x91]="PU1"  [0x92]="PU2" [0x93]="STS"
    [0x94]="CCH"  [0x95]="MW"   [0x96]="SPA" [0x97]="EPA"
    [0x98]="SOS"  [0x99]="SGCI" [0x9A]="SCI" [0x9B]="CSI"
    [0x9C]="ST"   [0x9D]="OSC"  [0x9E]="PM"  [0x9F]="APC"
  )
  C1CtrlCharsAlt=(
    [0x01]="CA-A" [0x02]="CA-B" [0x03]="CA-C" [0x04]="CA-D"  [0x05]="CA-E" [0x06]="CA-F" [0x07]="CA-G"
    [0x08]="CA-H" [0x09]="CA-I" [0x0a]="CA-J" [0x0b]="CA-K"  [0x0c]="CA-L" [0x0d]="CA-M" [0x0e]="CA-N"
    [0x0f]="CA-O" [0x10]="CA-P" [0x11]="CA-Q" [0x12]="CA-R"  [0x13]="CA-S" [0x14]="CA-T" [0x15]="CA-U"
    [0x16]="CA-V" [0x17]="CA-W" [0x18]="CA-X" [0x19]="CA-Y"  [0x1a]="CA-Z" [0x1b]="CA-[" [0x1c]="CA-]"
    [0x1d]="CA-}" [0x1e]="CA-^" [0x1f]="CA-_" [0x20]="CA-SP" [0x7F]="A-DEL"
  )

  MouseButtons=(
    [0x00]="MB1-P" [0x01]="MB2-P" [0x02]="MB3-P" [0x03]="MB-R"
    [0x20]="MB1-M" [0x21]="MB2-M" [0x22]="MB3-M" [0x23]="MB-M"
    [0x40]="MB4-P" [0x41]="MB5-P"
  )
  MouseMetaButtons=(
    [0x04]="S-"    [0x08]="A-"    [0x0c]="AS-"
    [0x10]="C-"    [0x14]="CS-"   [0x1c]="CAS-"
  )

  AdjustMousePos() {
    local -i _INDEX
    ord_eascii _INDEX "${2}"
    eval ${1}'=$(( ${_INDEX}-32))'
  }
  GetMouseButton() {
    local MouseBtn
    AdjustMousePos MouseBtn "${2}"
    MouseBtn="${MouseMetaButtons[$(( ${MouseBtn} & 0x1C))]-}${MouseButtons[$(( ${MouseBtn} & 0xe3))]}"
    eval ${1}='"${MouseBtn}"'
  }

  vtparser_callback_readkey() {
    unset UInput[@]
    case "${1}" in
      ${VTPARSE_ACTION_ESC_EXECUTE})
        case "${2}" in
          [[:cntrl:]])
            UInput[0]="${C1CtrlCharsAlt[${3}]:-$(printf "%q" $'\e'"${2}")}"
            ;;
          *)
            UInput[0]="${C1CtrlChars[${3}]:-$(printf "%q" $'\e'"${2}")}"
            ;;
        esac
        ;;
      ${VTPARSE_ACTION_EXECUTE})
          UInput[0]="${C0CtrlChars[${3}]:-$(printf "%q" "${2}")}"
        ;;
      ${VTPARSE_ACTION_CSI_DISPATCH})
        case "${2}" in
          z) # Sun Function Keys
            UInput[0]="${SunKeybFntKeys[${vtparser_params[0]}]:-}"
            if [ -n "${UInput[0]}" ]; then
              UInput[0]="${KeyModifiers[${vtparser_params[1]:-1}]}${UInput[0]}"
              UInput[1]="1" # Repeat Count
            else
              UInput[0]="CSI ${vtparser_params[*]} ${2}"
            fi
            ;;
          '~') # Function Keys
            UInput[0]="${KeybFntKeys[${vtparser_params[0]}]}"
            if [ -n "${UInput[0]}" ]; then
              UInput[0]="${KeyModifiers[${vtparser_params[1]:-1}]}${UInput[0]}"
              UInput[1]="1" # Repeat Count
            else
              UInput[0]="CSI ${vtparser_params[*]} ${2}"
            fi
            ;;
          A|B|C|D|E|F|H|I|O|Z|P|Q|R|S)
            UInput[0]="${KeybFntKeysAlt[${3}]:-}"
            if [ -n "${UInput[0]}" ]; then
              UInput[0]="${KeyModifiers[${vtparser_params[1]:-1}]}${UInput[0]}"
              UInput[1]="${vtparser_params[0]:-1}" # Repeat Count
            else
              UInput[0]="CSI ${vtparser_params[*]} ${2}"
            fi
            ;;
          t)
            ${vtparser_read} 2
            UInput[0]="MouseTrack"
            AdjustMousePos UInput[1] "${REPLY:0:1}"
            AdjustMousePos UInput[2] "${REPLY:1:1}"
            ;;
          T)
            ${vtparser_read} 6
            UInput[0]="MouseTrack"
            AdjustMousePos UInput[1] "${REPLY:0:1}"
            AdjustMousePos UInput[2] "${REPLY:1:1}"
            AdjustMousePos UInput[3] "${REPLY:2:1}"
            AdjustMousePos UInput[4] "${REPLY:3:1}"
            AdjustMousePos UInput[5] "${REPLY:4:1}"
            AdjustMousePos UInput[6] "${REPLY:5:1}"
            ;;
          M)  # Mouse
            ${vtparser_read} 3
            GetMouseButton UInput[0] "${REPLY:0:1}"
            if [ -n "${UInput[0]}" ]; then
              AdjustMousePos UInput[1] "${REPLY:1:1}"
              AdjustMousePos UInput[2] "${REPLY:2:1}"
            else
              UInput[0]=$(printf 'Mouse-\\x%02x %q'  "'${escapeSequence:0:1}" "${escapeSequence:1}")
            fi
            ;;

          *)
            UInput[0]="CSI ${vtparser_params[*]} ${2}"
            ;;
        esac
        ;;
      ${VTPARSE_ACTION_SS3_DISPATCH})
        case "${2}" in
          A|B|C|D|E|F|H|P|Q|R|S|~)
            UInput[0]+="${KeybFntKeysAlt[${3}]}"
            if [ -n "${UInput[0]}" ]; then
              UInput[0]="${KeyModifiers[${vtparser_params[1]:-1}]}${UInput[0]}"
              UInput[1]="${vtparser_params[0]:-1}" # Repeat Count
            else
              UInput[0]="SS3 ${vtparser_params[*]} ${2}"
            fi
            ;;
          *)
            UInput[0]="SS3 ${vtparser_params[*]} ${2}"
            ;;
        esac
        ;;
      ${VTPARSE_ACTION_ESC_DISPATCH})
        case "${2}" in
          [][}^_A-Z]) UInput[0]="${C1CtrlChars[${3}]}" ;;
          [^[:cntrl:]]) UInput[0]="CA-${2}" ;;
          *) UInput[0]="${C1CtrlChars[${3}]:-$(printf "%q" $'\e'"${2}")}" ;;
        esac
        ;;
      ${VTPARSE_ACTION_PRINT})
        case "${2}" in
          [^[:cntrl:]]) UInput[0]="${2}" ;;
          *) UInput[0]="${C0CtrlChars[${3}]:-$(printf "%q" $'\e'"${2}")}" ;;
        esac
        ;;
      *)
        vtparser_callback_debug "${@}" || return $?
        ;;
    esac
    return 1

  }

   HandleKey() {
        vtparse_init vtparser_callback_readkey vtparse_read_stdin
        while true; do
                vtparse
                case "${UInput[0]}" in
                        LF)
                                echo "${UInput[@]}"
                                break
                                ;;
                        *up)       echo "Up Arrow ignoring modifier keys"  ;;
                        down)      echo "Down Arrow No modifier keys"      ;;
                        S-down)    echo "Shift + Down Arrow"               ;;
                        A-down)    echo "Alt + Down Arrow"                 ;;
                        AS-down)   echo "Alt + Shift + Down Arrow"         ;;
                        C-down)    echo "Control + Down Arrow"             ;;
                        CS-down)   echo "Control + Shift + Down Arrow"      ;;
                        CA-down)   echo "Control + Alt + Down Arrow"        ;;
                        CAS-down)  echo "Control + Alt + Shift + Down Arrow";;
                        MCAS-down) echo "Meta + Control + Alt + Shift + Down Arrow";;
                        *)
                                echo "${UInput[@]}"
                                ;;
                esac
        done

   }
HandleKey

KEYBD trap (ksh93)

ksh93 provides lower-level control over interactivity that is extensible directly in the shell language. The special KEYBD trap, if set, will fire on any keypress while exposing the necessary primitives to handle the event through special parameters.

For example, after running trap 'printf %q\\n "${.sh.edchar}"' KEYBD, a representation of each key pressed will be printed back in shell-escaped format. Using this information, you can use the trap to call a function from an array of callbacks or commands to evaluate associated with certain keypresses or combinations.

TODO: example. This should be enough to get you going.