Homework & Coursework Questions

#! /bin/bash

#Takes arguments to determin the GCD

errorNum="Too many or too few arguments passed."
errorUse="Usage: $0 [decimal] [decimal]"
errorNeg="Cannot use a negative number."

checkIfZero ()
{
if [ $a=0 ]
then
drop=1
elif [ $b=0 ]
then
drop=1
else
drop=0
fi
exit 0
}

if [ $1 < 1 -o $2 < 1 ]
then
echo $errorNeg
echo $errorUse
exit 0
fi

if [ $# -le 1 -o $# -gt 2 ]
then
echo $errorNum
echo $errorUse
exit 0
elif [ $1 -ge 0 ] && [ $2 -ge 0 ]
then
a=$1
b=$2
drop=0
while [ $a -gt 0 ] || [ $b -gt 0 ]
do
if [ $a -gt $b ]
then
if [ drop -gt 0 ]
then
checkIfZero
c=`expr $a % $b`
a=$c
fi
elif [ $b -gt $a ]
then
if [ drop -gt 0 ]
checkIfZero
c=`expr $b % $a`
b=$c
fi
fi
done

if [ $a -gt $b ]
then
echo "The GCD is $a."
else
echo "The GCD is $b."
fi
fi

if [ $# -lt 2 ]
then
           echo "Wrong usage"
           exit -1
elif [ $1 -le 0 -o $2 -le 0 ]
then
           echo "Invalid args"
           exit -1
fi

#get the smallest of 2 args and store it in $div

a=$1
b=$2
if [ $a -lt $b ]
then
           div=$a
elif [ $b -lt $a ]
then
           div=$b
else
           div=$a
fi
#loop from $div to 1 till $div divides both $a and $b completly

while [ $div -gt 0 ]
do
           remA=`expr $a % $div`
           remB=`expr $b % $div`
           if [ $remA -eq 0 -a $remB -eq 0 ]
           then
                      echo "GCD of $a and $b is $div"
                      exit 0
           fi
           div=`expr $div - 1`
done
echo "GCD of $a and $b is 1"
exit 0

#! /bin/bash
y=$1; r=$2
while [ $r -ne 0 ]
do
    gcd=$r
    r=$(($y % $r))
    y=$gcd
done
echo $gcd