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Date difference

Posted on 2003-12-01
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Last Modified: 2013-12-26
Hi,

Is there a way to find out the month difference between two dates in UNIX shell script?

Thanks
Roy
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Question by:dib_roy
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9 Comments
 
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Expert Comment

by:liddler
ID: 9849308
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Accepted Solution

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mbekker earned 125 total points
ID: 9849517
Hi dib_roy,

To determine only the number of months you could try the following script:

#!/usr/bin/ksh

monthstr_to_num()
{
 case "$1" in
   Jan) echo "1" ;;
   Feb) echo "2" ;;
   Mar) echo "3" ;;
   Apr) echo "4" ;;
   May) echo "5" ;;
   Jun) echo "6" ;;
   Jul) echo "7" ;;
   Aug) echo "8" ;;
   Sep) echo "9" ;;
   Oct) echo "10" ;;
   Nov) echo "11" ;;
   Dec) echo "12" ;;
 esac
}

echo "$1" | read month1 year1
echo "$2" | read month2 year2

year_diff=$(( ( $year2 - $year1 ) * 12 ))  # in months...
month_diff=$(( $(monthstr_to_num $month2) - $(monthstr_to_num $month1) ))
total_diff=$(( $month_diff + $year_diff ))
echo "Difference between the months $month1 $year1 and $month2 $year2 is: $total_diff"


Usage: month_diff <"month1 year1"> <"month2 year2">

It depents on how the datestamps look like. Perhaps the months are already in numbers so you could leave out the convert part.

If you've got normal datestamps like:

   Mon Dec  1 12:40:32 CET 2003

you can awk,sed,cut,... the parts out you want. In this example it would be:
awk {'print $2 " " $6'}

Good luck!
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Assisted Solution

by:HamdyHassan
HamdyHassan earned 125 total points
ID: 9850539

You could check Perl
use Time::Local;

http://www.perldoc.com/perl5.6/lib/Time/Local.html


for example to get yesterday date using perl

use Time::Local;
$today = timelocal(localtime);
# Subtract 1 day
@yesterday = localtime($today - (24 * 60 * 60));
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Expert Comment

by:ozo
ID: 9854428
$today = timelocal(localtime);
is a roundabout way of saying
$today = time;


What is the format of the dates you wish to find the difference of?
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Expert Comment

by:cluedon
ID: 10027173

hard with a shell script, easy with a perl script.    If perl is an option you shoud repost your question in a perl section.
you should also post the format of the dates you want to compare, there are a lot of variations.

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Expert Comment

by:ozo
ID: 10027457
How many months difference is there between 2003-12-31 and 2004-01-01?
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Author Comment

by:dib_roy
ID: 10027675
Thanks everybody for your help. I got my answer.

Roy
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Expert Comment

by:liddler
ID: 10241346
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

Points split mbekker & HamdyHassan

Please leave any comments here within the next seven days.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

liddler
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