Shell Programming and Scripting

And you don't want to subtract 1 from the year, should the month be January?

Sharma331! I just finished a script tailored for the date format required in post #1 ((m)m-(d)d-yyyy)and in the meantime you posted a complete different date format?! Please check if the below code is working for the date format mentioned in post #1, if yes, we can simply adapt it to yyyy-mm-dd

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Following is a beginner level approach, obviously, but it seems to work and fulfil OPs expectations at 100%. Tested on SunOS' 5.10 date and ksh.

Code:

month=`date '+%m' | tr -d ' '`
day=`date '+%e' | tr -d ' '`
year=`date '+%Y'`

currentDate="$month/$day/$year"

case $month in
    1) year=`expr $year - 1`; month=12
    ;;
    *) month=`expr $month - 1`
    ;;
esac

oneMonthBefore="$month/$day/$year"

It looks perfect... Let me try this and get back to you!!

Try your code on the following March 30, 2014. There is no February 30th.

Because months vary in length 28,29,39, and 31 days finding the previous month means that there have to be some assumptions made by your accounting folks

for example:

Define: last month = "30 days ago". If this operation results in a date in 2 months ago, like March 1 minus 30 days is in January, make a correction. If it results in the first day of the same month, make a correction.

Also this whole date thing is covered in a lot of posts here on the forums by CFA Johnson. He has a website with a really set of bash functions for doing date arithmetic. Perderabo also has datecalc posted on the forums as a sticky (I think it is still there). The Gregorian calendar is messy to work with. IMO, reinventing something that has existing, working code is a bad idea. Writing code to learn about it is great. Just don't use somewhere that has the potential get you fired. Like a payroll application.

Thanks Junior helper!! it works perfectly.

Hi.

For this specific question, a ksh solution:

Code:

printf "%(%b, %B, %m)T\n"  "last month"

producing:

Code:

Oct, October, 10

on a system:

Code:

OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian 5.0.8 (lenny, workstation) 
ksh 93s+

See also dateutils

Best wishes ... cheers, drl