I am new to shell scripting.. I want a script to get any date as a input from user and print date of 3 days back?
example: If user enters date as 2013-01-01 then output should be
2012-12-29.
2 Answers
If you have GNU date, then this will work:
user_date=2013-01-01
date +%Y-%m-%d -d "$user_date - 3 days"
With BSD date, you'd have to do like this:
user_date=2013-01-01
date -j -v -3d +%Y-%m-%d -d "${user_date//-}0000"
because BSD date needs date to be in the format YYYYmmddHHMM.
I don't have a Solaris now to test there. If you're in Solaris then hopefully there is gdate, and you can use the first option, just replace the date command with gdate.
Whichever OS you are in, there are two important points:
- In what format can you pass dates to the
datecommand. I tested that GNU date can acceptYYYY-mm-ddformat (and probably many others), while BSD needsYYYYmmddHHMM. - In what format can you ask for a difference. With GNU date simply
DATE - 3 daysworks, with BSD date it's trickier with-j -v -3dflags.
man date of your system should help you get through these hurdles. In the worst case, you could do all the date operations you need in perl or similar.
Comments
You can just do:
date --date="3 days ago"
to get get date of 3 days back.
