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List:       linux-admin
Subject:    Re: Special date/cal needs eg. "thrid friday of july"
From:       "Adam T. Bowen" <adam.bowen () connectinternetsolutions ! com>
Date:       2007-01-12 15:02:44
Message-ID: 45A7A314.9090904 () connectinternetsolutions ! com
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Hi,

Martin Klier wrote:
> Hi Linux Admins,
> 
> is there a command to get something like "thrid friday of july" or "second 
> wednesday each month"? I crossread the manuals for date and gcal, but it 
> seems to be impossible. Next thing I found was gcal, with 
> "--period-of-fixed-dates", but I have not been able to get useful results, 
> and 
> date -d "35 tuesday" (35th tuesday of a year), but I have not been able to 
> limit it to months nor selecting the year (by the way, I do not need it).
> 
> Has somebody experience with this one, and can you give me a hint where to 
> look, or even an example?
> 
> Thanks a lot in advance,

I love the --date GNU extension, but I tried a number of different
syntaxes to get it to do what you wanted without any luck.  So I thought
a one line pipe would be fun:

cal 7 2007 | awk -F. 'NR > 2{print substr($1,5*3+1,2)}' | grep '[0-9]' |
awk 'NR == 3 {print $1}'

You set the day you're interested in through the first integer of the
second parameter of the substr call of the awk command.  0=Sunday
(0*3+1), 1=Monday (1*3+1) etc.  You set the week number with the 'NR ==
n' part of the final awk.  You set the month and year with the
parameters to cal.  It invokes awk twice which if used in a very tight
loop could be a problem.  It would be easy to merge the awk | grep | awk
into one awk command, but it starts to look more like program code on a
single line rather than a series of simple(-ish) commands.

Cheers

Adam
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