Date Subtraction

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# 1  
Old 12-09-2013
Date Subtraction

Hello All,
I am a newbie to unix shell scripting and need to write a script that displays the difference between two variables that stores date value.

For example,
F1=`ls -ltr file1* | tail -1 |tr -s ' ' |cut -d' ' -f6,7,8`
F2=`ls -ltr file2* | tail -1 |tr -s ' ' |cut -d' ' -f6,7,8`

F1 and F2 stores the values like Aug 02 06:54(month,date and time). I need to find the difference between these two variables. I tried using expr and just regular subtraction which doesnt work. Can you please help me understand how to do date arithmetic in unix?

I tried searching and found some stuff like date -d option which doesnt work in my case.

Please share your valuable suggestions.


Last edited by Franklin52; 12-10-2013 at 04:17 AM.. Reason: Please use code tags
# 2  
Old 12-10-2013
Take a look at this: Link
# 3  
Old 12-10-2013
Thanks for the link. I did look into that link before, but it calculates only date difference. I need to find both date and time difference. Can you please advice how to convert the date I get using ls command into generic format? Aug 02 11:23 into 20130802 11:23
# 4  
Old 12-10-2013
Originally Posted by priyaa2010
... I need to find both date and time difference ...
       ddiff - manual page for ddiff 0.2.3

       ddiff [OPTION]... DATE/TIME [DATE/TIME]...

       ddiff 0.2.3

       Compute duration from DATE/TIME (the reference date/time) to the other
       DATE/TIMEs given and print the result as duration. 

This is part of -- the source can be downloaded as a zip file. Some GNU/Linux distributions also have it packaged up, e.g. Debian jessie

A sample calculation from man ddiff:
         % ddiff 2012-03-01T12:17:00 2012-03-02T14:00:00

Best wishes ... cheers, drl
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