pgkeys.sh

#!/bin/bash

# Toggle a swap of the PageUp/PageDown keys with Home/End (X11 / xmodmap).
#   PageUp   <-> Home
#   PageDown <-> End
#
# Usage:
#   togglepgkeys.sh          toggle based on current state
#   togglepgkeys.sh on       force the swap on
#   togglepgkeys.sh off      restore defaults

if [ "$XDG_SESSION_TYPE" != "x11" ]; then
  echo "error: requires an X11 session (xmodmap has no effect on Wayland)." >&2
  exit 1
fi

swap_on() {
  xmodmap -e "keycode 112 = Home" \
          -e "keycode 117 = End" \
          -e "keycode 110 = Prior" \
          -e "keycode 115 = Next"
  echo "PageUp/PageDown <-> Home/End swap: ON."
}

swap_off() {
  xmodmap -e "keycode 112 = Prior" \
          -e "keycode 117 = Next" \
          -e "keycode 110 = Home" \
          -e "keycode 115 = End"
  echo "PageUp/PageDown <-> Home/End swap: OFF (defaults restored)."
}

case "$1" in
  on)  swap_on ;;
  off) swap_off ;;
  "")
    # No argument: detect state from keycode 112 (physical PageUp).
    current=$(xmodmap -pke | awk '$1=="keycode" && $2==112 {print $4}')
    if [ "$current" = "Home" ]; then
      swap_off
    else
      swap_on
    fi
    ;;
  *)
    echo "usage: $0 [on|off]   (no argument = toggle)" >&2
    exit 1
    ;;
esac