Error handling during FTP.

I have been asked to handle errors arising from ftp.

This code does not handle errors.

if test $# -ne 3
then
        echo "Usage: $0 <PROCESSING_DIR> <CURRENT_DIR> <FTP_DIR>"
        exit 1;
fi

process_dir=$1
current_dir=$2
ftp_dir=$3

cd $process_dir

ls CSH*.HIST > $current_dir/temp_file.txt
ls BSH*.HIST >> $current_dir/temp_file.txt
ls DSH*.hist >> $current_dir/temp_file.txt

cat $current_dir/temp_file.txt | \
while read line
do
wc -c $process_dir/$line > $current_dir/temp.txt
file_size=`awk '{print $1}' $current_dir/temp.txt`

 if [[ $file_size > 0 ]]; then  ##error needs to be handled from here.
    echo "
       user USERNAME PASSWORD
       lcd $process_dir
       bin
       prompt
       cd $ftp_dir
       mput $line
       bye
         " | ftp -ivn mopppgstrtadm6.pfizer.com
    echo "PDMA files successfully transferred to startrak."
 else
    echo "$line is a 0 byte PDMA file."
 fi
done   ##error needs to be handled till here.

rm -f  $current_dir/temp.txt
rm -f  $current_dir/temp_file.txt

I wish to replace the ftp code with this code:


 if [[ $file_size > 0 ]]; then  ##error needs to be handled from here.
    echo "
       user ibmpdma st4rtr4k!pdm4
       lcd $process_dir
       bin
       prompt
       cd $ftp_dir
       mput $line
       bye
         " | ftp -ivn mopppgstrtadm6.pfizer.com >> $LOG_FILE

      # testing the exit status of FTP
      egrep "Transfer complete" $LOG_FILE >/dev/null
      if [ $? = 0 ]
      then
         echo >> $LOG_FILE
         echo "FTP Successfully Done" >> $LOG_FILE
      else
         echo >> $LOG_FILE
         echo "FTP UnSuccessfull" >> $LOG_FILE
         exit 1
      fi

 else
    echo "$line is a 0 byte PDMA file."
 fi

but this code does not identify reason for failure:

I want to have something like FTP UnSuccessful due to:
1.non availability of space on the ftp server. or
2.incorrect username/password while logging into the ftp server. or
3.lcd and cd path not available.

How is this possible:


USERNAME AND PASSWORD REPLACED
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