copy file from rooted android device to linux pc

From Linux terminal, with connected rooted android device

adb shell
shell@hwChe2:/ $ cd data/data/com.example.android.pets/databases
 shelter.db                                                                   <
Unable to chmod shelter.db: Operation not permitted
10|shell@hwChe2:/data/data/com.example.android.pets/databases $ su
root@hwChe2:/data/data/com.example.android.pets/databases # chmod 777 shelter.db


From another Linux terminal

adb pull /data/data/com.example.android.pets/databases/shelter.db /home/