Copy file unless it does not already exist in target

backup.sh

SRC=/mnt/data/src1
TRG=/mnt/data/trg1

IFS=$'\n'
for f in $(ls -1 $SRC)
do
    if [[ -d $TRG/$f || -f $TRG/$f ]]; then
        echo "$f already exists!"
    else
        echo "Moving $f..."
        mv "$SRC/$f" $TRG
    fi
done