Ou alternativamente:
repodir=/some/path
backupdir=/some/otherpath
maxagedays=6
for repo in repo_A repo_B repo_X; do
svnadmin dump $repodir/$repo | bzip2 -9 > $backupdir/$repo-'date +%F'.dump.bz2
done
find /$backupdir -type f -iname *dump.bz2 -mtime +$maxagedays -exec rm -f {} \;