#!/bin/bash 

# Count up and down between the two numbers A and B
# repeatedly, while at the same time up and down between number A and C.



x=+
y=+
A=50
B=250
C=`expr \( $B - $A \) \* 2`
D=10
I=$A
I2=$A
X=1

until [ $X = 1000 ]; do

if [ $I -ge $B ]; then
	z="-"
	I=`expr $B - \( $I - $B \)`
elif [ $I -le $A ]; then
	z="+"
	I=`expr $A + \( $A - $I \)`

elif [ $I2 -ge $C ]; then
	y="-"
	I2=`expr $J - \( $I2 - $J \)`

elif [ $I2 -le $A ]; then
	y="+"
	I2=`expr $A + \( $A - $I \)`
fi

I=`expr $I $z $D`
I2=`expr $I2 $y $D`
let X=$X+1
echo " X = $X "
echo " I = $I "
echo " I2 = $I2"
done