Bash script for creating destination diff folder between two source folders

create_diff.sh

#!/bin/bash

programname=$0

function usage {
    echo "usage: $programname -l folder1 -r folder2 -d folder3 [-e lrd]"
    echo "  -l      folder on the left side"
    echo "  -r      folder on the right side"
    echo "  -d      destination folder"
    echo "  -e      exclude l (left side), r (right side) or d (differ)"
    exit 1
}

while getopts "l:r:d:e:" option; do
    case "${option}" in
        l) LEFT_FOLDER=${OPTARG};;
        r) RIGHT_FOLDER=${OPTARG};;
        d) DEST_FOLDER=${OPTARG};;
        e) EXCLUDE=$OPTARG;;
    esac
done

if [[ -z $LEFT_FOLDER || -z $RIGHT_FOLDER || -z $DEST_FOLDER ]]; then
    usage;
fi

diff -rq $LEFT_FOLDER $RIGHT_FOLDER | while read -r line ; do
    set -f;
    linearray=($line);
    set +f;
    
    if [[ $line = *"differ"* && ! $EXCLUDE = *"d"* ]]; then
        filepath_full=${linearray[3]};
        filepath=${filepath_full%/*};
        dest_filepath=$(echo "$filepath" | sed "s#${RIGHT_FOLDER}/\{0,1\}##g");
        filename_base=${filepath_full##*/};

        if [[ -z $dest_filepath ]]; then
            dest_path="$filename_base";
        else
            dest_path="$dest_filepath/$filename_base";
        fi

        echo "Differ: copy $filepath_full to $DEST_FOLDER/$dest_path";
        mkdir -p "$DEST_FOLDER/$dest_filepath" && cp -R $filepath_full "$DEST_FOLDER/$dest_path" 2>/dev/null;
    fi
    if [[ $line = *"Only in $LEFT_FOLDER"* && ! $EXCLUDE = *"l"* ]]; then
        lpart=${linearray[2]};
        rpart=${linearray[3]};
        filepath_full=${lpart%?}/$rpart;
        dest_filepath=$(echo "${lpart%?}" | sed "s#${LEFT_FOLDER}/\{0,1\}##g");

        if [[ -z $dest_filepath ]]; then
            dest_path="$filename_base";
        else
            dest_path="$dest_filepath/$rpart";
        fi

        echo "Left: copy $filepath_full to $DEST_FOLDER/$dest_path";
        mkdir -p "$DEST_FOLDER/$dest_filepath" && cp -R "$filepath_full" "$DEST_FOLDER/$dest_filepath/$rpart" 2>/dev/null;
    fi
    if [[ $line = *"Only in $RIGHT_FOLDER"* && ! $EXCLUDE = *"r"* ]]; then
        lpart=${linearray[2]};
        rpart=${linearray[3]};
        filepath_full=${lpart%?}/$rpart;
        dest_filepath=$(echo "${lpart%?}" | sed "s#${RIGHT_FOLDER}/\{0,1\}##g");

        if [[ -z $dest_filepath ]]; then
            dest_path="$filename_base";
        else
            dest_path="$dest_filepath/$rpart";
        fi

        echo "Right: copy $filepath_full to $DEST_FOLDER/$dest_path";
        mkdir -p "$DEST_FOLDER/$dest_filepath" && cp -R "$filepath_full" "$DEST_FOLDER/$dest_path" 2>/dev/null;
    fi
done