linux下拼接字符串的代码

DATA_DIR=/home/liupan/.navinsight/gm
result=""
for i in $(ls -a $DATA_DIR)
    do
        if [ $i != "." -a $i != ".." ]
        then
            result=$result$i","
        fi
    done
echo $result

该代码将data_dir下的所有文件夹的名字拼接成以逗号分隔的字符串