How many days until a certain date?

[Robert Comber]

Hi,

This should be simple but I can't seem to find a command that will work. I need to send out notices like "The system will be down for upgrades in 25 days." I can make a cron entry to call my script but my problem is that I can't find an easy way to calculate the number of days between the current date and some future date like July 4, 2003. This should be so easy but I'm stuck.

Thanks for any help,
Bob

[A. Clay Stephenson · Accepted solution]

Hi Bob:

This ain't no hill for a climber.

#!/usr/bin/sh
DATE="7 4 2003"
DAYS=$(($(caljd.sh ${DATE}) - $(caljd.sh)))
echo "Days until ${DATE} = ${DAYS}."

Pretty simple, huh?

[A. Clay Stephenson]

I suppose that we should also add some tests to only print if ${DAYS} >= 0

#!/usr/bin/sh
DATE="7 4 2003"
DAYS=$(($(caljd.sh ${DATE}) - $(caljd.sh)))
if [[ ${DAYS} -ge 0 ]]
then
echo "Days until ${DATE} = ${DAYS}."
fi

That should do it. Caljd.sh -u will give full usage.

[Robert Comber]

That was fast! I searched for caljd.sh and I got tons of hits.

Thanks,
Bob

[Adam J Markiewicz]

Hi Bob

Guess who wrote this script?
I suppose that out dear Albert installed some sort of sniffer that checks the subjects of new problems for words related with dates, time etc.
When the bell is ringing he drops everything and rush to the nearest keyboard. ;)

No points please.
No offense A.

Good luck
Adam

[Sergejs Svitnevs]

and my simple script...

#! /bin/sh
#future date = July 4, 2003 (04-07-2003)
#current date
day=`date +%d`
month=`date +%m`
year=`date +%y`
doj=`date +%j`
new_day=4
new_month=7
i=1
daycount=0
while [ $i -lt $new_month ]
do
monthlength=`cal $i $year|awk '/[0-9]/{last=$NF}END {print last}'`
daycount=`expr $daycount + $monthlength`
i=`expr $i + 1`
done
((daycount+=new_day))
daycount=`expr $daycount - $doj`
echo $daycount" days between the current date and July 4, 2003"

Regards,
Sergejs