[SOLVED] How to calculate current, previous and next year quarter in Shell Script?

Issue

I need to calculate the current, previous and next year quarter from the current sysdate in the below format.

As per current date (02-Nov-2020), current quarter should be returned as 20204, previous quarter as 20203, next quarter as 20211. It should be dynamic and should work for all the date/ month. I am trying with some approach like below but it doesn't seems to be working. Please help me with this. Thanks in advance.

curr_yrqtr=$(date +%Y)$(( ($(date +%-m)-1)/3+1 ))
prev_yrqtr=$(date -d "-1 month" +%Y)$(( ($(date -d "-1 month" +%-m)-1)/3+1 ))

Solution

Seeing how the question has several different flags (bash, ksh, perl), I'm guessing the OP is open to any solution that generates the desired results.

If the OP's version of date includes support for the %q (quarter) format:

read -r curr_year curr_qtr < <(date '+%Y %q')

If the OP's version of date does not support the %q (quarter) format:

read -r curr_year curr_month < <(date '+%Y %m')
curr_qtr=$((curr_month / 3 + 1))

From here the rest of the code is the same regardless of the version of date:

prev_year="${curr_year}"
prev_qtr=$((curr_qtr - 1))

next_year="${curr_year}"
next_qtr=$((curr_qtr + 1))

case "${curr_qtr}" in
    1) prev_year=$((curr_year - 1)) ; prev_qtr=4 ;;
    4) next_year=$((curr_year + 1)) ; next_qtr=1 ;;
esac

echo "previous quarter : ${prev_year}${prev_qtr}"
echo "current  quarter : ${curr_year}${curr_qtr}"
echo "next     quarter : ${next_year}${next_qtr}"

Running the above where 'today' == 2 Nov 2020:

previous quarter : 20203
current  quarter : 20204
next     quarter : 20211

Answered By - markp-fuso