Shell Script (Get old date from current date)

[Chen Yingjie]

I want to create a shell script to get
old date from current date.

For example,

I can get the current by `/usr/bin/date +%Y%m%d`.

How to get the old date(14 days before) from above current date?

Thanks for advise.

[Fred Ruffet]

You can use caljd from A.Clay Stephenson.
In shell flavor :
http://mirrors.develooper.com/hpux/caljd-2.23.sh
or perl one :
http://mirrors.develooper.com/hpux/caljd-2.2.pl

It's a you-can-do-anything-with-date program.

Regards,

Fred

[Chen Yingjie]

Thanks for reply.

Is there another way to slove this question?

Chen

[Fred Ruffet]

Yes. One more : Install GNU version of date. You will be then able to use something like :
date '14 days ago'

Regards,

Fred

[A. Clay Stephenson]

Your problem is trivially easy if you use the afore-mentioned caljd.sh utility.

#!/usr/bin/sh

DATEMINUS14=$(caljd.sh -y -s $(caljd.sh -p 14))
echo "14 days ago was ${DATEMINUS14}"

All of the calculations are done in just two functions cal_jdate and jdate_cal so if you like you can simply yank those out and put themn in your script. Invode as caljd.sh -u for full usage and many examples.

[Manuel Contreras]

I really like this solution, got It from this site.
enjoy,
manuel


today
$ date '+%b-%d'
Aug-13

- 1 day
$ perl -e 'print scalar localtime (time -1 * 86400),"\n"'
Thu Aug 12 14:03:33 2004

- 13 days
$ perl -e 'print scalar localtime (time -13 * 86400),"\n"'
Sat Jul 31 14:04:01 2004

yesterday
$ perl -e 'print scalar localtime (time -1 * 86400),"\n"' | awk '{print $2"-"$3}'
Aug-12

tomorrow
$ perl -e 'print scalar localtime (time +1 * 86400),"\n"' | awk '{print $2"-"$3}'
Aug-14

[Chen Yingjie]

I tried the Perl command listed above.
But it doesnot work on my server.

My server's OS is HP-UX 11.00.

Chen

[A. Clay Stephenson · Accepted solution]

Well, if you insist on a Perl solution, here you go in your format but caljd.sh (or caljd.pl) is much easier:

#!/usr/bin/sh

DT14BEFORE=$(perl -e '($year,$mon,$day) = (localtime(time() - (14 * 86400)))[5,4,3]; printf("%04d%02d%02d\n",$year + 1900,$mon + 1,$day)') # all of this is one line
echo "14 Days ago = ${DT14BEFORE}"

[Chen Yingjie]

Thank you sir.

I have confirmed it work.

Chen Yingjie

[Markus Miller]

Hi,

there is a little script that calculates the date in the past.

# Comand line argument: Amount of days in the past
PAST=$1

DATE=`date +%Y%m%d`
DATE=`expr $DATE - $PAST`
YEAR=`echo $DATE | cut -b 1,2,3,4`
DAY=`echo $DATE | cut -b 7,8`
MONTH=`echo $DATE | cut -b 5,6`
if [ "$DAY" = "00" ]
then
DATE=`expr $DATE - 100`
MONTH=`echo $DATE | cut -b 5,6`
if [ "$MONTH" = "00" ]
then
MONTH=12
DATE=`expr $DATE - 10000`
YEAR=`echo $DATE | cut -b 1,2,3,4`
fi
x=`cal $MONTH $YEAR`
DAY=`(for i in $x; do echo $i; done;) | tail -1`
fi

YEAR=`echo $YEAR | cut -b 3,4`
HOUR=`date +%H`
MINUTE=`date +%M`
# Here you can change the output
DATE="${MONTH}${DAY}${HOUR}${MINUTE}${YEAR}"

echo $DATE

Regards
Markus

[Manuel Contreras]

Chen, I just ran it on our 10.20 box:

manny> perl -e 'print scalar localtime (time -1 * 86400),"\n"'
Wed Dec 1 07:59:25 2004
manny> date
Thu Dec 2 07:59:28 PST 2004



maybe it's the version of perl:
manny> perl -v

This is perl, v5.6.0 built for 9000/777-hpux



the following is from an 11.00 box:
> perl -e 'print scalar localtime (time -1* 86400),"\n"'
Wed Dec 1 08:01:42 2004
> date
Thu Dec 2 08:01:44 PST 2004

[Chen Yingjie]

Thanks for all reply.