I need to write an Unix Shell Script tran.sh that moves the csv input files from /exp/files folder to /exp/ready directory.

The csv input files are written to /exp/files folder by an FTP server whose behavior I cannot trivially change. In tran.sh shell script I need to ensure before doing a move of that csv input file from /exp/files directory no longer any other process is writing to the file.

How can I do it.