UNIX for Dummies Questions & Answers

echo Enter a number
read no
i=1
ans=0
while [ "$i" -le "$(expr $no / 2)" ]
   do
       if [ `expr $no % $i` -eq 0 ]
       then
          ans=`expr $ans + $i`
       fi
       i=`expr $i + 1`
done
if [ $no -eq $ans ]
then
echo $no is perfect
else
echo $no is NOT perfect
fi

while [ "$i" -le "$(expr $no / 2)" ]

#  cat perfect.sh
#!/bin/sh
echo Enter a number
read no
i=1
ans=0
while [ $i -le `expr $no / 2` ]
   do
       if [ `expr $no % $i` -eq 0 ]
       then
          ans=`expr $ans + $i`
       fi
   i=`expr $i + 1`
  done
if [ $no -eq $ans ]
then
echo $no is perfect
else
echo $no is NOT perfect
fi

#  ./perfect.sh
Enter a number
6
6 is perfect

#  ./perfect.sh
Enter a number
28
28 is perfect

#  ./perfect.sh 
Enter a number
8
8 is NOT perfect

#  cat perfect.awk
nawk 'BEGIN {
 t=0
 printf("Enter a Number (or q to quit): ")
}

$0 ~ /^(quit|[qQ]|exit|[Xx])$/ { exit }

{
for (i=1;i<=$1/2;i++) { if (int($1/i)*i==$1){t+=i}}
if (t==$1){print $1" is perfect"} else {print $1" is not perfect"}
}

{
 t=0
 printf("Enter another Number (q to quit): ")
}' -

#  ./perfect.awk
Enter a Number (or q to quit): 1
1 is not perfect
Enter another Number (q to quit): 6
6 is perfect
Enter another Number (q to quit): 28
28 is perfect
Enter another Number (q to quit): 7
7 is not perfect
Enter another Number (q to quit): q