putting a math calculation in a cron job

the_rhino · 10-11-2004, 09:44 AM

I have a cron job

Getting a script called "backup" and it is cranking out a new directory and moving some files for me everyday like this

SHELL=/bin/bash
today=$(date +%m%d%y)
mkdir /home/user_name/serverbackup/serverbackup$today
mv /home/user_name/serverbackup/*.tar.gz --target-directory=/home/user_name/serverbackup/serverbackup$today

It works great, now I want to add another command to the script to remove the directory that is 8 days old, so, that I have the current seven days directories.

I have looked at man pages date and expr they don't help.

I am working my way through Rute and it does not give me anything to work with yet.

I haven't found anything useful on google or ldp.org

I do not know the syntax to make this work. I know that some how I need to have the script calculate the date that is 8 days from the current date so that I would end up with it looking for a directory like this:

today = serverbackup101104

8 days back from today's date = serverbackup100404

then the script would remove serverbackup100404 and the contents of that directory.

I suppose this part of the script is going to be a little more complex than the part I am using now.

Will anyone point me in the right direction so I can learn how to do this?

Thanks for the help,
The Rhino

DaHammer · 10-11-2004, 11:57 AM

Assuming your directory names always start with "serverbackup" followed by the "mmddyy", then this should work:

Code:

#!/bin/sh
# cleanup.sh

cleanup()
{
  for file in `ls`;
    do
      oldday=`echo $file | cut -c 15,16`;
      namechk=`echo $file | cut -c 1,2,3,4,5,6,7,8,9,10,11,12`;
      if test -d $file && test "$namechk" == "serverbackup"; then
        diff=`expr $thisday - $oldday`
        if test $diff -gt 7; then
          echo "$file: $diff days old - Removing"
          #rm -rf $file
        else
          echo "$file: $diff days old"
        fi;
      fi;
  done;
}

today=`date +%m%d%y`
thisday=`echo $today | cut -c 3,4`
cleanup

Given a directory with the following contents:

Code:

cleanup.sh*          serverbackup100404/  serverbackup100704/  serverbackup101004/  testfile
serverbackup100204/  serverbackup100504/  serverbackup100804/  serverbackup101104/  testfile.txt
serverbackup100304/  serverbackup100604/  serverbackup100904/  testdir/

the output would be:

Code:

serverbackup100204: 9 days old - Removing
serverbackup100304: 8 days old - Removing
serverbackup100404: 7 days old
serverbackup100504: 6 days old
serverbackup100604: 5 days old
serverbackup100704: 4 days old
serverbackup100804: 3 days old
serverbackup100904: 2 days old
serverbackup101004: 1 days old
serverbackup101104: 0 days old

Notice I left the "rm -rf $file" commented. You should throughly test this before actually enabling that. Placing a dynamic "rm" in a shell script makes me cringe with thoughts of $file somehow ending up being equal to "/" and then getting executed as root.

There is somewhat of a sanity check in place though, since it makes sure the directroy starts with "serverbackup" before it would remove it, but you may still want to include a few more safety nets. Anyway, you should at least get an idea of how you can calculate the difference in the dates on end of the file name.

Edit:
Oops, that won't work when the month and/or year changes, sorry.

homey · 10-11-2004, 12:37 PM

The find utility has time calculation features like modification time ( mtime ) and access time ( atime ) so you can search for files or directories which are older than or newer than the present time. Be careful when using the rm command, especially if you use it with -rf

#Delete old directories with the following command
find /home/user_name/serverbackup/* -type d -mtime +192 -exec rm -rf {} \;

#Delete old text files with the following command
find /home/user_name/serverbackup -type f -name '*.txt' -mtime +192 -exec rm {} \;

DaHammer · 10-11-2004, 01:46 PM

Here is a correction to what I did above, still using the directory name itself. You'll need to switch your date format to yymmdd though for it to work.

Code:

#!/bin/sh

cleanup()
{
  for file in `ls`;
    do
      namechk=`echo $file | cut -c 1,2,3,4,5,6,7,8,9,10,11,12`;
      filedate=`echo $file | cut -c 13,14,15,16,17,18`;
      filesecs=`date -d "$filedate" +%s` # Get seconds since 00:00:00 1970-01-01 UTC
      if test -d $file && test "$namechk" == "serverbackup"; then
        diff=`expr $tsecs - $filesecs`
        days=`expr $diff / 86400`;
        if test $diff -gt 691200; then
          echo "$file: $days days old - Removing"
          #rm -rf $file
        else
          echo "$file: $days days old"
        fi;
      fi;
  done;
}

today=`date +%y%m%d`
tsecs=`date +%s` # Get seconds since 00:00:00 1970-01-01 UTC
cleanup