Decimal-Binary.sh

main() {
    if [ $# -ne 1 ]; then
        echo "You must provide only 1 number."
        exit 1
    fi
    re='^[0-9]+$'
    if ! [[ $1 =~ $re ]]; then
        echo "$1 is not a positive integer."
        exit 1
    fi
    echo "Conversion of a decimal number $1 to its binary representation."
    number=$1
    reminder=1
    binary_representation=" "
    while [ "$number" -gt 0 ]
    do
        reminder=$(( number % 2))
        binary_representation="$binary_representation$reminder"
        number=$(( number / 2))
    done
    i=${#binary_representation}
    result=" "
    while [ "$i" -gt 0 ]
    do
        rev=$(echo "$binary_representation" | awk '{ printf substr( $0, "$i",1 ) }')
        result="$result$rev"
        i=$(( i - 1 ))
    done
    echo "Binary representation: $result"
}
main "$@"