Seeking help w/BASH script

[da2357]

Hi. I have a script that uses rsync to create several daily backups of selected folders. I have an external Firewire drive that's partitioned into two volumes---with one volume for the rsync backup. In the script, before it runs rsync, it tars the previous backup into a .tgz file stored on the second volume, thus leaving me a number of backup sets. I use several launchd agents to run the backup at pre-defined times. Everything in this script works fine.

As the second volume fills, I now want to add to my script so that when available space is under 20GB, it begins deleting the oldest backup sets until there's at least 20GB free. This is where I'm stuck. I've figured out that I can use this command that will find out how much free space is left:

FREESPACE = `df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`

but I'm not sure how to structure a while, until, or for loop to just delete enough of the oldest .tgz backups to leave me with 20GB of available space.

Suggestions? Ideas?

[barriehie]

Something like: (pseudocode going on here!)

declare -i FREESPACE
FREESPACE = `df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`
while [ $FREESPACE -lt 20GB ]
do
ls -1tr | head --lines=1 | read line
file=$line
rm /path_to_file/$file
done

[da2357]

Something like: (pseudocode going on here!)

declare -i FREESPACE
FREESPACE = `df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`
while [ $FREESPACE -lt 20GB ]
do
ls -1tr | head --lines=1 | read line
file=$line
rm /path_to_file/$file
done

This isn't working yet. I've got:

cd /Volumes/backup_02
FREESPACE=`df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`
while [ $FREESPACE -lt 10240 ]
do
ls -1 | read FILETODELETE
rm -f $FILETODELETE
FREESPACE=`df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`
done

More ideas and suggested code?

[lomcevak]

hmm, the manpage for df doesn't list the -m option but it still works. Anyway your problem may be that the Filesystem is so long that the rest of the info is listed the another line.

/root> df -hm
Filesystem           1M-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol01
                         38747      3397     33350  10% /

Try adding the -P option.

/root> df -hmP
Filesystem         1048576-blocks      Used Available Capacity Mounted on
/dev/mapper/VolGroup00-LogVol01     38747      3397     33350      10% /

[da2357]

OK, I've just tried the following. It at least deletes files, BUT it deletes all files and doesn't break out of the loop as I think it should.

for i in *.tgz
do
rm -f $i
FREESPACE=`df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`
if ($FREESPACE -lt 10240); then
break
fi
done

[da2357]

hmm, the manpage for df doesn't list the -m option but it still works. Anyway your problem may be that the Filesystem is so long that the rest of the info is listed the another line.

/root> df -hm
Filesystem           1M-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol01
                         38747      3397     33350  10% /

Try adding the -P option.

/root> df -hmP
Filesystem         1048576-blocks      Used Available Capacity Mounted on
/dev/mapper/VolGroup00-LogVol01     38747      3397     33350      10% /

I don't think the problem is with my FREESPACE command:

FREESPACE=`df -hm | grep '/Volumes/backup_02' | awk '{print $4}'`

but is with the loop processing the files. If I use "echo $FREESPACE" just after the above command, it correctly shows the amount of free megabytes.

[lomcevak]

OK. Your code looks correct. I'd suggest running the script in verbose mode so you can see what it's doing. Redirect the output to a file because you'll get a lot.

sh -vx /path/to/script > /tmp/log 2>&1