UNIX- Adding days to datetime variable

Shell Programming and Scripting
1

Hello All,

I have a date with timestamp stored in a variable and another variable which stores no. of days.

Var1=2014-12-11 12:54:21
Var2=5

In my unix script, I have to add the no. of days stored in var2 with the var1 date.
Var3=var1+var2=2014-12-16 12:54:21

Can you please advise if there is any unix function similar to dateadd MS SQL Server function. I tried using date -d argument,
but it is not supported in our environment.

Thank you in advance for your valuable suggestions.

2

What is your OS, shell, date version?

3

It is AIX version 6.

4

It would be a breeze if you know perl and it is installed on that machine...

5

The short answer is no. You cannot write shell script command to do date arithmetic.

http://www.unix.com/unix-for-dummies-questions-and-answers/4870-days-elapsed-between-2-dates.html\#post16559

This is code perderabo put together specifically to answer date questions.

6

Hi.

Some possibilities:

	
Date, time arithmetic, math
	1) gnu date

	2) ksh (version 93, not 88) printf

	3) date.pl (limited arith, but "date.pl -d '- 1 day'" works)
	   ( http://www.unix.com/tips-tutorials/
	   239167-general-purpose-date-script.html)

	4) dconv et al, e.g. ddiff
	   ( dateutils: http://www.fresse.org/dateutils/ )

	5) tm2tm (, OK in 32-bit; fails to compile in 64-bit)
	   ( http://www.unix.com/shell-programming-scripting/
	   146216-date-difference-between-freebsd-linux.html#post302463136 )

	6) perl custom (with function strftime)

	7) date-cpan.pl, cpan perl date
	   ( http://cpansearch.perl.org/src/CWEST/ppt-0.14/
	   src/date/date.jgross )

Best wishes ... cheers, drl

7

I believe the default ksh on AIX is a ksh88 version. To do date arithmetic with the ksh printf , you need a 1993 or later version of ksh . I believe many AIX systems have a another Korn shell installed as ksh93 that will do what is wanted here.

1 Like
8

I'd be most interested if the ksh93 installed on AIX version 6 supports the %T printf format. Certainly in AIX 5.3, which comes with a much older ksh93 (version ksh93n I believe) this wasn't supported.

@Nikita1981, Please report if this command works for you:

$ ksh93 -c 'printf "%T\n" "Dec 14 11:59"'
9

Thank you for all your valuable suggestions. I am planning to use database to get this done.

@Chubler_XL: No, the command doesn't work.