How to determine if a file is done copying

I have a file repository in a directory where files are copied into it by ftp or samba. Some of the ftp transfers can be slow, and some of the files can be fairly large. The files are not being used for anything in this directory other than being taken out of the directory and used by the system (every 30 minutes). My question is this, Is there any slick unix command line utility that I can run that would tell be if it is okay to deal with the file. In other words, is the file stable (in size) and not being currently copied into the directory at that very point in time (in which case I will ignore the file for now, or wait on it...).

Similar question here...

during ftp after specifying username/password

you can type

hash

while it is putting or getting files it will create #################################

until the copying ends

but I do not know how many bytes every # is represented.