Shell script to automate sftp transfer - linux

Question

I'm trying to create a shell script to automate the sftp transfer from source server to remote server without prompting for password. But when I run the script I get the output that no file is found for transfer (I have created files in the source directory). Here is my code
tempfile="/tmp/sftpsync.$$"
count=0
trap "/bin/rm -f $tempfile" 0 1 15
if [ $# -eq 0 ] ; then
echo "Usage: $0 user host path_to_src_dir remote_dir" >&2
exit 1
fi
# Collect User Input
user="$1"
server="$2"
remote_dir="$4"
source_dir="$3"
timestamp="$source_dir/.timestamp"
# Without source and remote dir, the script cannot be executed
if [[ -z $remote_dir ]] || [[ -z $source_dir ]]; then
echo "Provide source and remote directory both"
exit 1
fi
echo "cd $remote_dir" >> $tempfile
# timestamp file will not be available when executed for the very first time
if [ ! -f $timestamp ] ; then
# no timestamp file, upload all files
for filename in $source_dir/*
do
if [ -f "$filename" ] ; then
# Place the command to upload files in sftp batch file
echo "put -P \"$filename\"" >> $tempfile
# Increase the count value for every file found
count=$(( $count + 1 ))
fi
done
else
# If timestamp file found then it means it is not the first execution so look out for newer files only
# Check for newer files based on the timestamp
for filename in $(find $source_dir -newer $timestamp -type f -print)
do
# If found newer files place the command to upload these files in batch file
echo "put -P \"$filename\"" >> $tempfile
# Increase the count based on the new files
count=$(( $count + 1 ))
done
fi
# If no new files found the do nothing
if [ $count -eq 0 ] ; then
echo "$0: No files require uploading to $server" >&2
exit 1
fi
# Place the command to exit the sftp connection in batch file
echo "quit" >> $tempfile
echo "Synchronizing: Found $count files in local folder to upload."
# Main command to use batch file with SFTP shell script without prompting password
sftp -b $tempfile "$user#$server"
echo "Done. All files synchronized up with $server"
# Create timestamp file once first set of files are uploaded
touch $timestamp
# Remove the sftp batch file
rm -f $tempfile
exit 0
But I always get the output as "No files require uploading to $server". Would like to check if there is any issue with my code or how can this be fixed?