sftp conditional scripting

Some days, I need to send two files, other days, only one. The remote
site sends a warning email if the second file I send is empty. I
would like to avoid that.

I have looked at several web pages, but I am unclear as to how to
create the needed code.

I don't know how to test this as the remote site just grabs files that
are uploaded.

I also don't know if the script can (or how to do it) determine if a
file is essentially empty. First thought was to set an environment
variable based on result of RTV (can't remember which command to use,
but I have used it - just not in front of my terminal)

The current script does this, from memory:

expect "sftp>" put {$LOCALFILE} {$RMTFILE}
expect "sftp>" put {$LCLFILE2} {$RMTFILE2}
expect "sftp>" send "exit\n"

I haven't found an example to conditionally send a file, but I can see
that it can be done. Just don't know the syntax.

Thanks.

John McKee