initial commit
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Fabio Scotto di Santolo
226
chapter13/float_subtract.ksh
Executable file
226
chapter13/float_subtract.ksh
Executable file
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#!/usr/bin/ksh
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#
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# SCRIPT: float_subtract.ksh
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# AUTHOR: Randy Michael
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# DATE: 02/23/2007
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# REV: 1.1.A
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#
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# PURPOSE: This shell script is used to subtract a list of numbers.
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# The numbers can be either integers or floating-point
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# numbers. For floating-point numbers the user has the
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# option to specify a scale of the number of digits to
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# the right of the decimal point. The scale is set by
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# adding a -s or -S followed by an integer number.
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#
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# EXIT STATUS:
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# 0 ==> This script completed without error
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# 1 ==> Usage error
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# 2 ==> This script exited on a trapped signal
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#
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# REV. LIST:
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#
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#
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# set -x # Uncomment to debug this script
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# set -n # Uncomment to debug without any command execution
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#
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########################################################
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############## DEFINE VARIABLE HERE ####################
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########################################################
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SCRIPT_NAME=`basename $0` # The name of this shell script
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SCALE="0" # Initialize the scale value to zero
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NUM_LIST= # Initialize the NUM_LIST to NULL
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COUNT=0 # Initialize the counter to zero
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MAX_COUNT=$# # Set MAX_COUNT to the total number of
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# command-line arguments
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########################################################
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################ FUNCTIONS #############################
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########################################################
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function usage
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{
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echo "\nPURPOSE: Subtracts a list of numbers\n"
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echo "USAGE: $SCRIPT_NAME [-s scale_value] N1 N2...Nn"
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echo "\nFor an integer result without any significant decimal places..."
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echo "\nEXAMPLE: $SCRIPT_NAME 2048.221 65536 \n"
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echo "OR for 4 significant decimal places"
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echo "\nEXAMPLE: $SCRIPT_NAME -s 4 8.09838 2048 65536 42.632"
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echo "\n\t...EXITING...\n"
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}
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########################################################
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function exit_trap
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{
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echo "\n...EXITING on trapped signal...\n"
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}
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########################################################
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################ START OF MAIN #########################
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########################################################
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###### Set a Trap ######
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trap 'exit_trap; exit 2' 1 2 3 15
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########################
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# Check for at least two command-line arguments
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if (($# < 2))
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then
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echo "\nERROR: Please provide a list of numbers to subtract"
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usage
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exit 1
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fi
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# Parse the command-line arguments to find the scale value, if present.
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while getopts ":s:S:" ARGUMENT
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do
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case $ARGUMENT in
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s|S) SCALE=$OPTARG
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;;
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\?) # Because we may have negative numbers we need
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# to test to see if the ARGUMENT that begins with a
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# hyphen (-) is a number, and not an invalid switch!!!
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for TST_ARG in $*
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do
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if [[ $(echo $TST_ARG | cut -c1) = '-' ]] \
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&& [ $TST_ARG != '-s' -a $TST_ARG != '-S' ]
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then
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case $TST_ARG in
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+([-0-9])) : # No-op, do nothing
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;;
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+([-0-9].[0-9]))
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: # No-op, do nothing
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;;
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+([-.0-9])) : # No-op, do nothing
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;;
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*) echo "\nERROR: Invalid argument on the command line"
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usage
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exit 1
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;;
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esac
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fi
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done
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;;
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esac
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done
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########################################################
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# Parse through the command-line arguments and gather a list
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# of numbers to subtract.
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while ((COUNT < MAX_COUNT))
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do
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((COUNT = COUNT + 1))
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TOKEN=$1
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case $TOKEN in
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-s|-S) shift 2
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((COUNT = COUNT + 1))
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;;
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-s${SCALE}) shift
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;;
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-S${SCALE}) shift
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;;
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*) NUM_LIST="${NUM_LIST} $TOKEN"
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((COUNT < MAX_COUNT)) && shift
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;;
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esac
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done
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########################################################
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# Ensure that the scale is an integer value
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case $SCALE in
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+([0-9])) : # No-Op - Do Nothing
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;;
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*) echo "\nERROR: Invalid scale - $SCALE - Must be an integer"
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usage
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exit 1
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;;
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esac
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########################################################
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# Check each number supplied to ensure that the "numbers"
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# are either integers or floating-point numbers.
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for NUM in $NUM_LIST
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do
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case $NUM in
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+([0-9])) # Check for an integer
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: # No-op, do nothing.
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;;
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+([-0-9])) # Check for a negative whole number
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: # No-op, do nothing
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;;
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+([0-9]|[.][0-9]))
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# Check for a positive floating-point number
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: # No-op, do nothing
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;;
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+(+[0-9]|[.][0-9]))
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# Check for a positive floating-point number
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# with a + prefix
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: # No-op, do nothing
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;;
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+([-0-9]|.[0-9]))
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# Check for a negative floating-point number
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: # No-op, do nothing
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;;
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+(-[.][0-9]))
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# Check for a negative floating-point number
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: # No-op, do nothing
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;;
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+([+.0-9]))
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# Check for a positive floating-point number
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: # No-op, do nothing
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;;
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*) echo "\nERROR: $NUM is NOT a valid number"
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usage
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exit 1
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;;
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esac
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done
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########################################################
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# Build the list of numbers to subtract
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SUBTRACT= # Initialize the SUBTRACT variable to NULL
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MINUS= # Initialize the MINUS variable to NULL
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# Loop through each number and build a math statement that
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# will subtract the numbers in the list.
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for X in $NUM_LIST
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do
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# If the number has a + prefix, remove it!
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if [[ $(echo $X | cut -c1) = '+' ]]
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then
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X=$(echo $X | cut -c2-)
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fi
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SUBTRACT="$SUBTRACT $MINUS $X"
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MINUS='-'
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done
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########################################################
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# Do the math here by using a here document to supply
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# input to the bc command. The difference of the numbers is
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# assigned to the DIFFERENCE variable.
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DIFFERENCE=$(bc <<EOF
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scale=$SCALE
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(${SUBTRACT})
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EOF)
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########################################################
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# Present the result of the subtraction to the user.
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echo "\nThe difference of: $SUBTRACT"
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echo "\nis: ${DIFFERENCE}\n"
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