My solution to Neil's bash masterclass exercise

guess.sh

#/bin/bash
#
# Number guessing game.
# A simple demo of bash capabilities
#
# [email protected]

readonly MaxGuesses=6
readonly Timeout=10

function validate {
    local answer="$1"
    local interactive=$2
    local status=1;
    case "$answer" in
    [0-9]|[0-9][0-9]|100)
        : OK
        status=0
        ;;
    [0-9]*)
        $interactive && echo "Look, I said a number between 1 and 100"
        ;;
    *)
        $interactive && echo "D'oh! I need a number!"
        ;;
    esac

    (( status != 0 )) && ! $interactive && echo "?"

    return $status
}

interactive=true
if getopts n option
then
    if [[ $option = 'n' ]]
    then
        interactive=false
    elif [[ $option = '?' ]]
    then
        echo "Usage: $0 [-n]" >&2
        exit 2
    fi
fi

typeset -i magic=$((RANDOM % 100 + 1))

$interactive && cat <<EOF
I've thought of a number between 1 and 100.
You've got $MaxGuesses attempts to try to guess it.
Oh and you've only got $Timeout seconds for each guess!
Good luck!
EOF

typeset -i guess
typeset -a prompt

if $interactive
then
    hiMsg="Sorry, that's too high"
    loMsg="Sorry, that's too low"
    timeoutMsg="\nWhoops, too slow! You've lost a life ..."
else
    hiMsg=">"
    loMsg="<"
    timeoutMsg=""
fi

for ((guess = 1; guess <= MaxGuesses; guess++))
do
    if $interactive
    then
        prompt=(-p "What's your guess? [$guess/$MaxGuesses] ")
    else
        prompt=()
    fi

    read -t $Timeout ${prompt[0]:+"${prompt[@]}"} answer

    (( $? > 128 )) && {
        echo -e $timeoutMsg
        continue
    }

    validate $answer $interactive || continue

    if (( answer == magic ))
    then
        # Got it
        break
    elif (( answer < magic ))
    then
        echo $loMsg
    else
        echo $hiMsg
    fi
done

status=1
if ((guess > MaxGuesses))
then
    $interactive && echo "I win! My number was $magic"
    $interactive || echo $magic
else
    $interactive && echo "Congratulations! You win!"
    status=0
fi

exit $status

guesser.sh

#!/bin/bash
#
# Plays the guessing game (see guess.sh above)

trap 'rm -f guesses replies' EXIT

mkfifo guesses replies
exec 3<> guesses
exec 4<> replies

(./guess.sh -n ; echo 'Correct!') < guesses > replies &

guess=50
min=0
max=100

while : ; do
  if [ $guess -eq 69 ]; then
    echo Guessing $guess, dude!
  else
    echo Guessing $guess
  fi
  echo $guess > guesses
  read response < replies
  echo Got back $response
  case $response in
    '<')
      new_min=$guess
      guess=$((max - ((max - guess) / 2)))
      min=$new_min
      ;;
    '>')
      new_max=$guess
      guess=$((guess - (guess - min)/ 2))
      max=$new_max
      ;;
    *)
      exit
      ;;
  esac
done