Write a shell script to display the calendar for current month with current date replaced by * or ** depending on whether the date has one digit or two

Write a shell script to display the calendar for current month with current date replaced by * or ** depending on whether the date has one digit or two in unix/linux

if (( $(date "+%d") <= 9 ))

then

cal|sed -r "s/\b$(date "+%d")\b/*/"

else

cal|sed -r "s/\b$(date "+%d")\b/**/"

fi