added new menu functions

lib/skel/.bashrc.d/functions

@@ -128,3 +128,100 @@ ctrl_c(){
 
 # ensure ctrl-c to cancel script ends the entire process and not just the current function
 trap ctrl_c INT
+
+# Renders a text based list of options that can be selected by the
+# user using up, down and enter keys and returns the chosen option.
+#
+#   Arguments   : list of options, maximum of 256
+#                 "opt1" "opt2" ...
+#   Return value: selected index (0 for opt1, 1 for opt2 ...)
+select_option(){
+
+  # little helpers for terminal print control and key input
+  ESC=$( printf "\033")
+  cursor_blink_on()  { printf "$ESC[?25h"; }
+  cursor_blink_off() { printf "$ESC[?25l"; }
+  cursor_to()        { printf "$ESC[$1;${2:-1}H"; }
+  print_option()     { printf "   $1 "; }
+  print_selected()   { printf "  $ESC[7m $1 $ESC[27m"; }
+  get_cursor_row()   { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }
+  key_input()        { read -s -n3 key 2>/dev/null >&2
+                    if [[ $key = $ESC[A ]]; then echo up;    fi
+                    if [[ $key = $ESC[B ]]; then echo down;  fi
+                    if [[ $key = ""     ]]; then echo enter; fi; }
+
+  # initially print empty new lines (scroll down if at bottom of screen)
+  for opt; do printf "\n"; done
+
+  # determine current screen position for overwriting the options
+  local lastrow=`get_cursor_row`
+  local startrow=$(($lastrow - $#))
+
+  # ensure cursor and input echoing back on upon a ctrl+c during read -s
+  trap "cursor_blink_on; stty echo; printf '\n'; exit" 2
+  cursor_blink_off
+
+  local selected=0
+  while true; do
+    # print options by overwriting the last lines
+    local idx=0
+    for opt; do
+      cursor_to $(($startrow + $idx))
+      if [ $idx -eq $selected ]; then
+        print_selected "$opt"
+      else
+        print_option "$opt"
+      fi
+      ((idx++))
+    done
+
+    # user key control
+    case `key_input` in
+      enter) break;;
+      up)    ((selected--));
+          if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi;;
+      down)  ((selected++));
+          if [ $selected -ge $# ]; then selected=0; fi;;
+    esac
+  done
+
+  # cursor position back to normal
+  cursor_to $lastrow
+  printf "\n"
+  cursor_blink_on
+
+  return $selected
+}
+
+# Example for above select_option
+#echo "Select one option using up/down keys and enter to confirm:"
+#echo
+
+#options=("one" "two" "three")
+
+#select_option "${options[@]}"
+#choice=$?
+
+#echo "Choosen index = $choice"
+#echo "        value = ${options[$choice]}"
+
+select_opt(){
+  select_option "$@" 1>&2
+  local result=$?
+  echo $result
+  return $result
+}
+
+# Examples for above select_opt
+#case `select_opt "Yes" "No" "Cancel"` in
+#  0) echo "selected Yes";;
+#  1) echo "selected No";;
+#  2) echo "selected Cancel";;
+#esac
+
+#options=("Yes" "No" "${array[@]}") # join arrays to add some variable array
+#case `select_opt "${options[@]}"` in
+#  0) echo "selected Yes";;
+#  1) echo "selected No";;
+#  *) echo "selected ${options[$?]}";;
+#esac