code: def _remote_file_size_unix(self, remote_cmd="", remote_file=None):
          
          if remote_file is None:
              if self.direction == "put":
                  remote_file = self.dest_file
              elif self.direction == "get":
                  remote_file = self.source_file
          remote_file = "{}/{}".format(self.file_system, remote_file)
          if not remote_cmd:
              remote_cmd = "ls -l {}".format(remote_file)
  
          self.ssh_ctl_chan._enter_shell()
          remote_out = self.ssh_ctl_chan.send_command(remote_cmd, expect_string=r"[\$#]")
          self.ssh_ctl_chan._return_cli()
  
          if "No such file or directory" in remote_out:
              raise IOError("Unable to find file on remote system")
  
          escape_file_name = re.escape(remote_file)
          pattern = r"^.* ({}).*$".format(escape_file_name)
          match = re.search(pattern, remote_out, flags=re.M)
          if match:
              # Format: -rw-r--r--  1 pyclass  wheel  12 Nov  5 19:07 /var/tmp/test3.txt
              line = match.group(0)
              file_size = line.split()[4]
              return int(file_size)
  
          raise ValueError(
              "Search pattern not found for remote file size during SCP transfer."
          )
docs: Get the file size of the remote file.