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# Date difference

Posted on 2003-12-01
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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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Expert Comment

ID: 9849308
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Accepted Solution

mbekker earned 500 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!
0

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Assisted Solution

HamdyHassan earned 500 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));
0

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Expert Comment

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?
0

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Expert Comment

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

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

ID: 10027675

Roy
0

LVL 18

Expert Comment

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

liddler
EE Cleanup Volunteer
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