Newbie scripting question, dates

Bubba235 · 10-27-2004, 04:00 PM

I am trying to automate backup scripts and I am able to create date specifc directories by using the string:
mkdir /hotbackup/$(date +%m%d%Y)
This creates a directory named /hotbackup/10272004 which is exactly what I want. The issue I am having is I can't figure out how to create/remove a directory from a previous day. I have tried
rm /hotbackup/$(date +%m%d%Y)-1
rm /hotbackup/$(date-1 +%m%d%Y)
rm /hotbackup/$(date +%m%d-1%Y)
and they all fail.
Any help would be greatly appreciated.
Thank you.

david_ross · 10-27-2004, 04:06 PM

You could use:
today=`date +%d`
yesterday=$(($today-1))

Note that you will also need to take into account the 1st of each month, especially in January.

Personally I like to use the unix time (%s) which is the number of seconds since 1970, this way you only need to know the number of seconds in a day etc and not wory about the archaic - near imposible to compute - gregorian calendar.

chort · 10-27-2004, 05:09 PM

If you don't do the time since epoch, you could use printf and a lot of manual calendar definition. I did this once in PERL and the results were good, but it takes a lot of thought with different number of days per month, roll over from one month to the next, one year to the next, daylight time, etc, etc... It seems simple until you start thinking about it...

On second thought, that time since epoch idea isn't looking so bad

Bubba235 · 10-27-2004, 05:10 PM

Thanks for the replies. I was hoping for a quick 'Do this -1' but it looks like it's going to be more difficult that that.

david_ross · 10-27-2004, 05:23 PM

If you are open to the idea of using perl then there is a "parsedate" function which is pretty good at taking a human readable date, changing it into the seconds since the epoch which can then be modified and turned back into a time using the localtime function.

homey · 10-28-2004, 03:51 PM

Normally, you use date in the file name so you can look at it and know when it was created. If you want to do something to that file based on it's creation date or other options, the find tool has several options ( man find ) like mtime , atime , ctime .

Here is an example where the backups and logs which are older than 3 months are deleted.

Edit: Guess I should make the err messages go to a separate file....
2> /mnt/backup/${filename}err.log

Code:

#!/bin/bash
filename=`date '+%m%d%y'`
/bin/tar -cvzf /mnt/backup/${filename}.tar.gz . \
> /mnt/backup/${filename}.log \
2> /mnt/backup/${filename}err.log
#Delete old files with the following command
find /mnt/backup -type f -name '*.gz' , -name '*.log' , \
-mtime +90 -exec rm {} \;

Bubba235 · 10-28-2004, 04:42 PM

Thank you, I think you solved the problem I was having, great job! I appreciate it.

homey · 10-28-2004, 05:51 PM

You're welcome!

Oh, I always charge extra if you appreciate it.

and just in case you change your mind

I charge double if you don't appreciate it.

subhasis_ray · 11-05-2004, 12:06 AM

Just one more way to do it.....

use the perl module Date::Manip, and create a script that takes in the number of days u want to go back, calculate the date and return it to u. All u need to do then is to call this script and pass it the number of days to go back...... your job is done

-Subhasis