ksh: ftp script to download files and check each file download correctly or not

This script is just a basic script to download files from a remote machine to local machine using ftp and see whether each file is correctly downloaded or not. cksum command is used to see that local file has same check sum as remote file. If the file is downloaded successfully, it will delete the file remotely.

#!/bin/ksh 

### check if already running
LOCKFILE="cs_frank_ftp.lock" #lockfile
NOFILESTODOWLOAD=64


if [ -f $LOCKFILE ]; then
 exit
fi
touch $LOCKFILE  # create your lockfile so that any process starting up after

_script_dir=`pwd`
_download_to_dir="/root/sriram_ftptesting/download"
_source_dir="/opt/sriram_testing"


_ftp_address="172.18.24.177"
_ftp_usr="Varun"
_ftp_pwd="root123"

[ -f $_script_dir/cksum_remote.lst ] && rm -f $_script_dir/cksum_remote.lst
[ -f $_script_dir/cksum_local.lst ] && rm -f $_script_dir/cksum_local.lst 

cd $_download_to_dir

ssh Varun@172.18.24.177 "cd $_source_dir; ls comps.* | while read file ; do cksum \$file ; done" > $_script_dir/cksum_remote.lst  2> /dev/null
[ ! -s $_script_dir/cksum_remote.lst ] && echo "No files in the remote location : $_source_dir : Please check,Exiting !!!!" && exit $NOFILESTODOWLOAD 


for file in `cat $_script_dir/cksum_remote.lst | awk '{print $NF}'` 

do
 echo "+++Opening FTP Session to download $file +++"
 _ftp_exec=`ftp -n -v $_ftp_address << EO_FTP
        user $_ftp_usr $_ftp_pwd
 prompt off
        binary
        cd $_source_dir
        get $file
        bye
    EO_FTP`
      
 cksum $file >> $_script_dir/cksum_local.lst
        cksum_expected=$(awk -v FILE=$file '$NF==FILE {print $1}' $_script_dir/cksum_remote.lst)                                                                          
        cksum_actual=$(awk -v FILE=$file '$NF==FILE {print $1}' $_script_dir/cksum_local.lst)                                                                             

        if [ $cksum_expected -eq $cksum_actual ] ; then
                echo "$file downloaded succesfully with checksum $cksum_actual same as expected: $cksum_expected"
                echo "removing $file from source  : $_source_dir"
                ssh Varun@172.18.24.177 "rm -f $_source_dir/$file"
                [ $? -eq 0 ] && echo "$file removed successfully"
        else

                echo "$file download not successful"
                echo "removing localcopy $file and try download once again"
        fi

done

rm -f $LOCKFILE

exit 0