I am using putty via the command line to get (using mget) all of the txt files on a remote server. I would like to only get the files for a specific date range or files that have not been previously downloaded.
Edit: should have been more specific. I need to do this over an sftp connection
Really sounds like you'll want to look at rsync. See Backing up Windows machines using rsync and ssh by Manu Garg.
Sounds like you are trying to synchronize data? If that is the case, perhaps try rsync?