UNIX for Advanced & Expert Users

I want to create a script to check if a file was downloaded into a folder. if it was i dont want to re-download it.

The requirement is as follows.
The first time the file (filename: A) is downloaded, it is renamed by stripping off part of the filename to filename A22.

The second time an attempt is made to download file A, it should not be downloaded, since it was downloaded and renamed already to A22.

Well, you are filtering the file names to download, so where do you get those names?

Suppose the file names are date based: file_YYYY-MM-DD.data

Code:

FILE_LOC=file_$( date '+%Y-%m-%d' )
 
if [ ! -f $FILE_LOC ]
then
 scp rem_user@rem_host:drop_dir/$FILE_LOC.data $FILE_LOC.tmp
 zret=$?
 
 if [ $zret != 0 -o ! -s $FILE_LOC.tmp ]
 then
  echo "Download failed ($zret):" >&2
  ls -l $FILE_LOC.tmp >&2
  exit 1
 else
  mv $FILE_LOC.tmp $FILE_LOC
  echo "Download complete:" >&2
  ls -l $FILE_LOC >&2
 fi
fi