Thank you for your kindly reply, let me try to explain my idea clearer.
Basically I am going to setup a ftp server, setup one account for incoming files with no download read and delete rights, and setup another for my personal account.
Once my friend upload files to my 'incoming' account, I want to write a script that would able to compare the 'incoming' folder in the 'incoming account' (ie /home/annoymous/uploader1/incoming) to the 'incoming' foder in my personal account (ie /home/ftp/my_own_personal_account/incoming), if the size of source folder is larger than the destination, it would copy the files to the destination folder, and do nothing if it is smaller.
I want to do this because I've got some other ftp user, I know I can do it easly from the shell, but the other ftp users have no access to the shell, so I want it to be done automatically for serveral intervals (say 2 times a day).
Besides, I also need help to write a script that help me the clear all files in a folder (ie /home/annoymous/uploader1/incoming OR /home/annymous/uploader*/incoming in batches), but in this case I will only need to to run manually.
Many thanks again of reading my 'long' question and I really appreciate your help.