Marginal Taxes Owed

tax_calc.sh

#!/bin/bash

GROSS=$1

if [[ -z "${GROSS}" ]];then
    echo "usage $0 <income>" >&2
    exit 1
fi

declare -a BRACKETS=('0 10' '8376 15' '34001 25' '82401 28' '171851 33' '373651 35')
NUM_BRACKETS=$(expr ${#BRACKETS[@]} - 1)
OWED=0

while [[ $NUM_BRACKETS -gt -1 ]];do
    AMT=$(echo ${BRACKETS[${NUM_BRACKETS}]} | cut -f 1 -d ' ')
    PRCT=$(echo ${BRACKETS[${NUM_BRACKETS}]} | cut -f 2 -d ' ')

    if [[ ${GROSS} -gt ${AMT} ]];then
        WRKNG=$(echo "float_scale=2; ${GROSS} - ${AMT}" | bc -q 2>/dev/null)
        TAX=$(echo "float_scale=2; ${WRKNG} * .${PRCT}" | bc -q 2>/dev/null)
        OWED=$(echo "float_scale=2; ${OWED} + ${TAX}" | bc -q 2>/dev/null)
        GROSS=${AMT}
    fi

    NUM_BRACKETS=$(expr ${NUM_BRACKETS} - 1)
done

echo $OWED