#!/bin/sh -u
#  $0  (no args)
# A script that loops printing integers, first up and then down.
# Some of the comments in this script are "teacher" comments that should
# never appear in student programs (or real-world programs).
# -IAN! idallen@ncf.ca  February 2002

export PATH=/bin:/usr/bin
umask 022

# Start and end of loop.
#
start=1
end=5
increment=1

# 1. Count UP.
# Purely numeric variables don't need quotes when used, because they don't
# ever contain shell special characters (such as wildcards).  You can quote
# them anyway, to remind yourself that [almost] all variables should be quoted.
#
i="$start"
while [ "$i" -le "$end" ]; do
	echo "i is $i"
	let i=i+increment
	sleep 1
done

# 2. Count DOWN.
# Trick: We put a minus sign in front of the positive increment value
# to enable the loop to count downward.  Note that the while loop itself
# is almost identical code to the loop code above.  With one small change,
# the two loops could be made into identical code and written ONCE.
# Less code is better code!
#
i="$end"
increment="-$increment"    # reverse the increment (make negative)
while [ "$i" -ge "$start" ]; do
	echo "i is $i"
	let i=i+increment
	sleep 1
done

exit 0