Compare file size of multiple files in an array [on hold]

Scenario: Ftp site has 100s of files. Once a day, all the .gz files are copied to an AWS site then renamed. Only the date is kept in the file name.

Some of the files corrupted during copy. A txt file was delivered with a snapshot of ALL the files and attributes from the FTP site.

I have to write a script that will

1. read the text file only for .gz files
2. convert the name of the file to the filename on the S3 site
3. Compare the file size from the txt file to the file size on the S3 server
4. If the file sizes doen't match, write the filename and percent diff out to a txt file.

This is what I have so far, which is not even close to working

Suggestions?:

# Create array from files in FTP site text file
    f=cat ftpfiles.txt | grep .gz | awk '{print $9,$5}' #this doesn't work

# Start ForEach loop for files in created array
    for f in *.gz
        do
    # Create variable for file size of source file
        file1size=$( cat $f | wc -c )

    # Create variable for file size of destination file
        fiesize2=aws s3 ls s3://folder1/folder2/$f | awk '{print $3}'

    #Compare sizes and print result to .txt file by percent diff
        echo "$f"

        if [ $file1size -lt $file2size ]; then
          size=$file1size
        else
            size=$file2size
        fi

        dc -e "
        3k
        $( cmp -n $size -l $file1 $file2 | wc -l )
        $size
        /
        100*
        p"

#close loop 
    done