An example of using rsync to backup three folders in Documents to an external drive, checking that it's mounted first

backup.sh

#!/bin/bash

output=/media/$USER/My\ Passport/vubuntu/
if [ ! -d "$output" ]; then
   echo "$output not found, is drive connected to computer?"
   exit 1
fi

for folder in "Personal" "Transcripts" "Resume"; do
    rsync -avzh /home/$USER/Documents/$folder $output
done