Various prompting tasks in bash

prompt_functs.sh

# This file is not intended to be executed.
# Source this script from other scripts.

# replacement for realpath on posix systems that lack it
findrealpath() {
  [ "$#" = 1 ] || { echo "usage: findpath path" >&2 ; return 1 ; }
  [ ! "$1" = "/" ] || { echo "/" ; return 0 ; }
  canonpath="$(cd "$(dirname "$1")" && pwd -P)" || return 1
  separator="/"
  [ ! "$canonpath" = "/" ] || separator=
  base="$(basename "$1")"
  if [ "$base" = "." ]
  then
    base=
    separator=
  fi
  path="$canonpath$separator$base"
  if [ -L "$path" ]
  then
    # if it IS a real path to a symlink, resolve it via recursive call
    path="$(readlink "$path")" || return 1
    if [ -d "$path" ]
    then
      $(cd "$path") || return 1
      findrealpath "$path" || return 1
    else
      echo "$path"
    fi
  else
    # if not a path to a real symlink, dont do anything further
    echo "$path"
  fi
}

_PROMPT_FUNCTS_TRIM=

_prompt_preproc ()
{
	local i
	i="$1"
	if [ -n "$_PROMPT_FUNCTS_TRIM" ]
	then
		i="$(echo "$i" | sed 's/^ *\| *$//g')"
	fi
	echo "$i"
}

# Makes it so all prompt functions trim input before reading it.
# $1 - If 0 (or none), turns off prompt trimming. If 1 (or anything else), turns
# it on.
set_prompt_trim ()
{
	if [ -z "$1" -o "$1" = 0 ]
	then
		_PROMPT_FUNCTS_TRIM=
	else
		_PROMPT_FUNCTS_TRIM=1
	fi
}

# Prompts, and if no input, returns a default.
# $1 - Prompt to show user
# $2 - What to return if user enters no input
prompt_default ()
{
	local inp
	read -p "$1 (default '$2'): " inp
	inp="$(_prompt_preproc "$inp")"
	if [ -z "$inp" ]
	then
		inp="$2"
	fi
	echo "$inp"
}

# Prompts until user enters integer.
# $1 - Prompt to show user
prompt_num ()
{
	local inp
	while true
	do
		read -p "$1 (integer): " inp
		inp="$(_prompt_preproc "$inp")"
		case "$inp" in
			''|*[!0-9]*) ;;
			*) break ;;
		esac
	done
	echo "$inp"
}

# Prompts user for integer. Returns default value if invalid value is entered.
# $1 - Prompt to show user
# $2 - What to return if user enters no input
prompt_num_default ()
{
	local inp
	read -p "$1 (default '$2'): " inp
	inp="$(_prompt_preproc "$inp")"
	case "$inp" in
		''|*[!0-9]*) inp="$2";;
		*) ;;
	esac
	echo "$inp"
}

# Prompts until user enters integer in given range.
# $1 - Prompt to show user
# $2 - Start of range (inclusive)
# $3 - End of range (inclusive)
prompt_range ()
{
	local range_start
	local range_end
	local inp
	range_start="$2"
	range_end="$3"
	if [ $range_start -gt $range_end ]
	then
		local t
		t=$range_start
		range_start=$range_end
		range_end=$t
	fi
	while true
	do
		inp=$(prompt_num "$1 (${range_start}-${range_end})")
		if [ $inp -ge $range_start -a $inp -le $range_end ]
		then
			break
		fi
	done
	echo "$inp"
}

# Prompts for integer in range. Returns default if user enters an invalid value.
# $1 - Prompt to show user
# $2 - Start of range (inclusive)
# $3 - End of range (inclusive)
# $4 - Default value
prompt_range_default ()
{
	local range_start
	local range_end
	local inp
	range_start="$2"
	range_end="$3"
	if [ $range_start -gt $range_end ]
	then
		local t
		t=$range_start
		range_start=$range_end
		range_end=$t
	fi
	inp=$(prompt_num_default "$1 (${range_start}-${range_end})" "$4")
	if [ $inp -lt $range_start -o $inp -gt $range_end ]
	then
		inp="$4"
	fi
	echo "$inp"
}

# Prompts for confirmation. Returns 1 if yes and nothing if no.
# $1 - Prompt to show user
prompt_confirm ()
{
	local inp
	while true
	do
		read -p "$1 (y/n): " inp
		inp="$(_prompt_preproc "$inp")"
		case $inp in
			[Yy]*)
				echo 1
				break
				;;
			[Nn]*)
				break
				;;
			*)
				;;
		esac
	done				
}

# Prompts for an item from a menu. The menu is paginated, with 10 menu items
# per page. The user is prompted until an item is selected.
# $1 - Prompt to show user. This will be at the top of the selection menu.
# $2-... - The options that the user may select from. This will also be return
#  value of this function
prompt_select()
{
	local items_per_page=10
	local prompt
	local -a options
	local -a page_options
	local inp
	local page=0

	# load args
	prompt="$1"
	shift
	while (( "$#" ))
	do
		options=("${options[@]}" "$1")
		shift
	done

	local print_linebreak=0
	while true
	do
		# get the options currently being displayed:
		local -a prev_opt=()
		local -a next_opt=()
		local item_count=$items_per_page
		local prior_items=$(( page * (items_per_page - 2) ))
		if [[ "$prior_items" -gt 0 ]]; then (( prior_items++ )); fi
		local remaining_items=$(( ${#options[@]} - prior_items ))
		if [[ "$remaining_items" -gt "$items_per_page" ]]
		then
			next_opt=("(next page)")
			(( item_count-- ))
		fi
		if [[ "$page" -gt 0 ]]
		then
			prev_opt=("(previous page)")
			(( item_count-- ))
		fi
		page_options=("${prev_opt[@]}" "${options[@]:$prior_items:$item_count}" "${next_opt[@]}")
		
		# print the prompt
		local opt_num=0
		local opt
		local menu_prompt="$prompt"
		if [[ $print_linebreak = 1 ]]
		then
			menu_prompt="
$menu_prompt"
		fi
		for opt in "${page_options[@]}"
		do
			menu_prompt="$menu_prompt
$opt_num) $opt"
			(( opt_num++ ))
		done
		menu_prompt="$menu_prompt
"

		# now get the input
		local max_opt=$(( ${#page_options[@]} - 1 ))
		inp=$(prompt_range "${menu_prompt}select" 0 $max_opt)
		print_linebreak=1
		if [[ ${#prev_opt[@]} != 0 && $inp = 0 ]]
		then
			(( page-- ))
		elif [[ ${#next_opt[@]} != 0 && $inp = $max_opt ]]
		then
			(( page++ ))
		else
			echo "${page_options[$inp]}"
			break
		fi
	done
}