Delete old backup folders over lftp / ftp

Question

I'm writing a small backup script for my Ubuntu server. The files are tar'ed and zipped locally to a temporary folder, uploaded to the ftp server via lftp and finally deleted locally.

Save files to the server:

FTPSUBDIR=`date --utc +"%Y-%m-%d"`
echo "mkdir -p /daily/${FTPSUBDIR}; mirror --reverse ${TEMPDIR} /daily/${FTPSUBDIR};" | /usr/bin/lftp -u "$FTPUSER,$FTPPASS" "$FTPSERV"

The folder structure on the ftp server:

/
  daily
    2011-10-25
    2011-10-24
    2011-10-23
  weekly
    2011-10-23
    2011-10-16
    2011-10-09

How do I keep only the x newest backups(5 for daily, 4 for weekly) and delete the other folders on the ftp server?

Answer 1

With just ftp operations on the remote system you would need to be more proactive on the ftp client side.

Non-debugged code fragments follow... you will have to flesh out and debug.

# print results of directory list to standard out
ftp_dir ()
{
  typeset dir="$1";
  ftp <<'FTP'
login
connection and
cd
directory commands
FTP
}

# read delete commands (or others) from stdin using inline login
ftp_delete()
{
   cat <<FTP - | ftp
send FTP login and delete commands
FTP
}

do_delete ()
{
   typeset dir="$1";
   typeset cnt="$2";
   if [ ${#names} -gt $cnt ]; then
          typeset a_end=$(( ${#names} - 8 ));
          ( typeset n=0;
            while [ $n -lt a_end ]; do
                echo "delete $dir/${names[$n]}";
                 n=$(( $n + 1 ));
             done; ) | ftp_delete
      fi
}

names=( $( ftp_dir weekly | sort ) );  #get all entries
do_delete dir 4

If I was more awake I might come up with a better answer.