Shell Programming and Scripting

#!/usr/bin/bash

a=15.42
b=13.03

c=`echo "scale=2;($a*$b)+.01" |bc -l`
echo $c

echo 205.5686 |  sed    's/\(\...\)[0-4].*/\1/;t;
         s/\(\..\)0.*/\11/;t
         s/\(\..\)1.*/\12/;t
         s/\(\..\)2.*/\13/;t
         s/\(\..\)3.*/\14/;t
         s/\(\..\)4.*/\15/;t
         s/\(\..\)5.*/\16/;t
         s/\(\..\)6.*/\17/;t
         s/\(\..\)7.*/\18/;t
         s/\(\..\)8.*/\19/;t
         s/\(\..\)9.*/\10/;t
        '
205.57

#!/bin/bash --posix
# Save IFS.
ifs_str="$IFS"
IFS="."
# Number with 3rd decinal place as 6. NOTE: no zero at the start but "-" instead!
summed_number=-.45677
# Create an array.
round=($summed_number)
# Ensure a roundup number!
roundup=9
# Print it to the terminal.
printf "%0.2f\n" ${round[0]}.${round[1]:0:2}$roundup
# Repeat above with 3rd decimal place as 3.
summed_number=1097.31367
round=($summed_number)
printf "%0.2f\n" ${round[0]}.${round[1]:0:2}$roundup
# Reset IFS.
IFS="$ifs_str"
# You now have the building blocks using bash builtins.
# I will leave you to create the required loops.

Last login: Fri Nov 15 18:44:29 on ttys000
AMIGA:barrywalker~> chmod 755 roundup.sh
AMIGA:barrywalker~> ./roundup.sh
-0.46
1097.32
AMIGA:barrywalker~> _

#!/bin/ksh93

a=15.42
b=13.33

c=$(printf "%.2f\n"  $(( a * b ))) 
echo $c

a=15.42
b=13.33
c=$(awk -v a=$a -v b=$b 'BEGIN {printf "%.2f\n",a*b}')
echo c$
205.55

a=15.42
b=13.33
c=`echo "$a*$b" | bc -l`
printf "%.2f\n" $c