mastering-unix-ss/chapter13/float_divide.ksh

#!/usr/bin/ksh
#
# SCRIPT: float_divide.ksh
# AUTHOR: Randy Michael
# DATE: 02/23/2007
# REV: 1.1.A
#
# PURPOSE: This shell script is used to divide two numbers.
#          The numbers can be either integers or floating-point
#          numbers. For floating-point numbers the user has the
#          option to specify a scale of the number of digits to
#          the right of the decimal point. The scale is set by
#          adding a -s or -S followed by an integer number.
#
# EXIT STATUS:
#      0 ==> This script exited normally
#      1 ==> Usage or syntax error
#      2 ==> This script exited on a trapped signal
#
# REV. LIST:
#
#
# set -x # Uncomment to debug this script
# set -n # Uncomment to debug without any command execution
#
########################################################
############## DEFINE VARIABLE HERE ####################
########################################################

SCRIPT_NAME=`basename $0`
SCALE="0"     # Initialize the scale value to zero
NUM_LIST=     # Initialize the NUM_LIST to NULL
COUNT=0       # Initialize the counter to zero
MAX_COUNT=$#  # Set MAX_COUNT to the total number of
              # command-line arguments

########################################################
################ FUNCTIONS #############################
########################################################

function usage
{
echo "\nPURPOSE: Divides two numbers\n"
echo "USAGE: $SCRIPT_NAME [-s scale_value] N1 N2"
echo "\nFor an integer result without any significant decimal places..."
echo "\nEXAMPLE: $SCRIPT_NAME 2048.221 65536 \n"
echo "OR for 4 significant decimal places"
echo "\nEXAMPLE: $SCRIPT_NAME -s 4 2048.221 65536"
echo "\n\t...EXITING...\n"
}

########################################################

function exit_trap
{
echo "\n...EXITING on trapped signal...\n"
}

########################################################
################ START OF MAIN #########################
########################################################

###### Set a Trap ######

trap 'exit_trap; exit 2' 1 2 3 15

########################

# Check for at least two command-line arguments
# and not more than four

if (($# < 2))
then
    echo "\nERROR: Too few command line arguments"
    usage
    exit 1
elif (($# > 4))
then
    echo "\nERROR: Too many command line arguments"
    usage
    exit 1
fi

# Parse the command-line arguments to find the scale value, if present.

while getopts ":s:S:" ARGUMENT
do
    case $ARGUMENT in
    s|S) SCALE=$OPTARG
         ;;
     \?) # Because we may have negative numbers we need
         # to test to see if the ARGUMENT that begins with a
         # hyphen (-) is a number, and not an invalid switch!!!

         for TST_ARG in $*
         do
            if [[ $(echo $TST_ARG | cut -c1) = '-' ]] \
               && [ $TST_ARG != '-s' -a $TST_ARG != '-S' ]
            then
                case $TST_ARG in
                +([-0-9])) : # No-op, do nothing
                           ;;
                +([-0-9].[0-9]))
                           : # No-op, do nothing
                           ;;
                +([-.0-9])) : # No-op, do nothing
                           ;;
                *) echo "\nERROR: $TST_ARG is an invalid argument\n"
                   usage
                   exit 1
                   ;;
                esac
            fi
         done
         ;;
    esac
done

########################################################

# Parse through the command-line arguments and gather a list
# of numbers to divide.

TOTAL_NUMBERS=0

while ((COUNT < MAX_COUNT))
do
    ((COUNT = COUNT + 1))
    TOKEN=$1
    case $TOKEN in
    -s|-S) shift 2
           ((COUNT = COUNT + 1))
           ;;
    -s${SCALE}) shift
           ;;
    -S${SCALE}) shift
           ;;
    *) ((TOTAL_NUMBERS = TOTAL_NUMBERS + 1))
       if ((TOTAL_NUMBERS == 1))
       then
           DIVIDEND=$TOKEN
       elif ((TOTAL_NUMBERS == 2))
       then
           DIVISOR=$TOKEN
       else
           echo "ERROR: Too many numbers to divide"
           usage
           exit 1
       fi
       NUM_LIST="$NUM_LIST $TOKEN"
       ((COUNT < MAX_COUNT)) && shift
       ;;
    esac
done

########################################################

# Ensure that the scale is an integer value

case $SCALE in
+([0-9])) : # No-op - Do Nothing
          ;;
*) echo "\nERROR: Invalid scale - $SCALE - Must be an integer"
   usage
   exit 1
   ;;
esac

########################################################

# Check each number supplied to ensure that the "numbers"
# are either integers or floating-point numbers.

for NUM in $NUM_LIST
do
    case $NUM in
    +([0-9])) # Check for an integer
              : # No-op, do nothing.
              ;;
    +([-0-9])) # Check for a negative whole number
              : # No-op, do nothing
              ;;
    +([0-9]|[.][0-9]))
              # Check for a positive floating-point number
              : # No-op, do nothing
              ;;
    +(+[0-9]|[.][0-9]))
              # Check for a positive floating-point number
              # with a + prefix
              : # No-op, do nothing
              ;;
    +([-0-9]|.[0-9]))
              # Check for a negative floating-point number
              : # No-op, do nothing
              ;;
    +(-.[0-9]))
              # Check for a negative floating-point number
              : # No-op, do nothing
              ;;
    +([+.0-9]))
              # Check for a positive floating-point number
              : # No-op, do nothing
              ;;
    *) echo "\nERROR: $NUM is NOT a valid number"
       usage
       exit 1
       ;;
    esac
done

########################################################

# Do the math here by using a here document to supply
# input to the bc command. The quotient of the division is
# assigned to the QUOTIENT variable.

QUOTIENT=$(bc <<EOF
scale=$SCALE
$DIVIDEND / $DIVISOR
EOF)

########################################################

# Present the result of the division to the user.

echo "\nThe quotient of: $DIVIDEND / $DIVISOR"
echo "\nto a scale of $SCALE is ${QUOTIENT}\n"