Sftp files from Remote server to local server - linux

Question

Sorry if it's too much simple question. But I am Java developer, no idea of shell scripting.
I googled, but couldn't find exactly what I am looking for.
My requirement
Connect to remote server using Sftp [authentication based on pub/pri
keys]. A variable to point to private key file
Transfer files with
specific extension [.log] to local server folder. Variable to set
remote server path and local folder
Rename the transferred file in
remote server
Log all the transferred files in a .txt file
Can any one give me shell script for this?
This is so far I framed from suggestions.
Still some questions left on my side ;)
export PRIVKEY=${private_key_path}
export RMTHOST=user#remotehost
export RMTDIR=/logs/*.log
export LOCDIR=/downloaded/logs/
export LOG=sucess.txt
scp -i $PRIVKEY $RMTHOST:$RMTDIR $LOCDIR
for i in 'ls -1 $LOCDIR/*.log'
do
echo $i >> $LOG
done
ssh $RMTHOST -c "for i in `ls -1 $RMTDIR; do mv /logs/$i /logs/$i.transferred; done"

Answer 1

What about this approach?
Connect to remote server using Sftp [authentication based on pub/pri keys]. A variable to point to private key file
Transfer files with specific extension [.log] to local server folder. Variable to set remote server path and local folder
scp your_user#server:/dir/of/file/*.log /your/local/dir
Log all the transferred files in a .txt file
for file in /your/local/dir/*.log
do
echo "$file" >> $your_txt
done
Rename the transferred file in remote server
ssh your_user#server -c "for file in /dir/of/file/*.log; do mv /dir/of/file/"$file" /dir/of/file/new_name_based_on"$file"; done"

Answer 2

Use scp(secure copy) command to transfer file. You may also want to add the -C switch, which compresses the file. That can speed things up a bit. i.e. copy file1 from server1 to server2,
On server1:
#!/bin/sh
scp -C /home/user/file1 root#server2.com:/home/user
Edit:
#!/bin/sh
scp -i {path/to/pub/pri/key/file} /home/user/file1 root#server2.com:/home/user