My rsync script to backup my data

backup.sh

#!/bin/bash
# backup-script for rsync/osx
#
#

#
# ----- Set Default Parameters -----
#

# folders to backup..
src_folders="/Users/gio/ /Library"

sc="scutil --get ComputerName"

# backup-target
if [[ $($sc | grep spar) == "spartacus" ]]; then
    dest_folder="/Volumes/data/MacBookPro_backup"
fi
if [[ $($sc | grep tele) == "telemaco" ]]; then
    dest_folder="/Volumes/data/iMac_backup"
fi

# location of hfs-enabled rsync-command
rsync_cmd="/usr/local/bin/rsync"

# excluded folders, separate with space, terminate with "/"
exclude_folders="Safari/Icons/ Caches/ .Trash/ *.app Steam/"

# rsync options
rsync_options="-aNHXsR --fileflags --delete-before --force-delete"

#
# ----- Check if params are reasonable -----
#

if [[ $rsync_cmd == "" ]]; then
   echo "no command given"
   exit 1
fi
if [[ ! -x $rsync_cmd ]]; then
   echo "$rsync_cmd is not executable"
   exit 1
fi
if [[ ! -d $dest_folder ]]; then
   echo "$dest_folder is not a directory"
   exit 1
fi
if [[ ! -w $dest_folder ]]; then
   echo "$dest_folder is not writable"
   exit 1
fi

# build exclude-options
for path in $exclude_folders; do
   exc_options="$exc_options--exclude \"$path\" "
done

# build cmdline
cmd="$rsync_cmd $rsync_options $additional_options $exc_options"

#
# ----- do rsync -----
#

for path in $src_folders; do
   cmd_here="$cmd $path $dest_folder"
   echo `date`" >> calling rsync for $path "
   eval $cmd_here
   echo " " 
done

echo "backup complete."
echo "Now unmounting disk"
diskutil umount /Volumes/data
zpool export data
exit 0