#!/bin/sh
# Copyright 2005 Daniel Cer (daniel.cer@cs.colorado.edu)
#
# This work is licensed under the Creative Commons Attribution-NonCommercial-
# ShareAlike License. To view a copy of this license, visit 
# http://creativecommons.org/licenses/by-nc-sa/2.5/ or send a letter to 
# Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 
# 94105, USA.

function fibonacci() {
  local fib=1; local prev_fib=1
  local next_prev_fib; local i
  if [ $1 -le 0 ]; then fibonacci_ret=-1; return; fi
  for i in `seq 2 $1`; do 
    next_prev_fib=$fib; fib=$[$fib+$prev_fib]; prev_fib=$next_prev_fib;
  done 
  fibonacci_ret=$fib;
}

if [ $# -ne 1 ]; then
  echo -e "Usage:\n\t$0 (n-th fibonacci # to calculate)" >&2
  exit -1
fi

fibonacci $1
echo "fibonacci($1): $fibonacci_ret"