bash next month error

Question

Running into errors. I am trying to get the next month when a user sends a date in.

D="2019/12/01";
D=$(date -d "$D");
echo "Current Date = $D";

prints Current Date = Sun Dec 1 00:00:00 EST 2019

current_month=$(date -d "$D" '+%m');
echo "Current Month = $current_month";

prints Current Month = 12

nextm=$(date -d "$D" "+next months");
echo "Next Month = $nextm";

prints Next Month = next months How do I get the next month?

**************** update ************************

D="2019/11/01";
D=$(date -d "$D");
echo "Current Date = $D";
Current Date = Fri Nov  1 00:00:00 EDT 2019
current_month=$(date -d "$D" '+%m');
echo "Current Month = $current_month";
Current Month = 11

next_date=$(date -d "$D next month")
echo "Next Date = $next_date";
Next Date = Sat Nov 30 23:00:00 EST 2019
next_year=$(date -d "$next_date" '+%Y');
echo "Next Year = $next_year";
Next Year = 2019

printing out november 30 instead of december 1

Answer 1

You can add one month to your input date string (using GNU date) like so:

nextm=$(date -d "$D +1 month")

Or:

nextm=$(date -d "$D next month")

When you quote $D and +next months separately that becomes two different parameters which will not be read by date in the way you want it to be.