#!/bin/sh -u
# A "while" loop reading user input - structured version with flag
# Syntax:   $0 number
# Purpose: loop reading input until the user types the given number
#
# NOTE: This script fragment is incomplete - it does not follow all
# the script guidelines set out in "script_style.txt".  It also
# contains some "Instructor-Style" comments that you must not use in
# your own scripts.  See script_style.txt for details.
#
# -IAN! idallen@idallen.ca

# Use standard search path, friendly umask, ASCII collating and sorting.
# Set the language and character set to be ASCII/C standard.
#
PATH=/bin:/usr/bin ; export PATH
LC_COLLATE=C ; export LC_COLLATE
LANG=C ; export LANG
umask 022

# Missing step: should validate input first - what if no argument is given?

# Loops that process input from the user pose a problem in shell
# programming - the shell doesn't have a "do ... while" or "do ...
# until" loop with a test at the bottom.  One way to code this is to
# prompt the user for the first guess before starting the loop; but,
# that duplicates a lot of code.  Below is one way of handling it without
# code duplication, using a flag variable that is set at loop bottom.

number="$1"
count=0
guessed="false"
while [ "$guessed" != "true" ] ; do
    let count=count+1

    # Prompt (always on stderr) for the input number.
    # Quick-exit the script if the user types EOF at the prompt.
    #
    echo 1>&2 "Try $count. Enter a guess for the number:"
    read guess || exit 1

    # Do some minimal validation of the input.
    # Missing step: should validate that input is an integer.
    #
    if [ -z "$guess" ] ; then
	echo 1>&2 "$0: Blank line - no guess - program exits"
	exit 1
    fi

    if [ "$guess" -eq "$number" ] ; then
	guessed="true"
    else
	# Tell the user the guess didn't match; give a hint.
	#
	echo "$count. guess '$guess' does not match the number"
	[ "$guess" -lt "$number" ] && echo " ... Too low."
	[ "$guess" -gt "$number" ] && echo " ... Too high."
    fi
done

echo "You guesed the number: $number"
echo "Tries: $count"

# script exits with the good return status of the last command