Tiny script used to backup folders

backup

#!/bin/bash
#
# backup - Tiny script used to backup folders. This
# is an exercise for learning shell programming.
#


#
# Join elements in array
#
function join() {
    local IFS="$1";
    shift;
    echo "$*";
}

source=('/Users/siyuan/notes' '/Users/siyuan/books')
target_dir='/Users/siyuan/backup'

target=$target_dir/$(date +"%Y%m%d%H%M%S").zip
# Craete target directory if it is not present
if ! [[ -e $target_dir ]]; then
    mkdir $target_dir
fi

sources=$(join ' ' "${source[@]}")
zip_command="zip -r $target $sources"

echo Zip command is:
echo $zip_command
echo Running:
$zip_command
if [[ $? = 0 ]]; then
    echo "Successful backup to $target"
else
    echo "Backup FAILED"
fi