code: public void changePermissions(String filename, String permissions)
  			throws SftpStatusException, SshException {
  
  		SftpFileAttributes attrs = new SftpFileAttributes(this,
  				SftpFileAttributes.SSH_FILEXFER_TYPE_UNKNOWN);
  		attrs.setPermissions(permissions);
  		setAttributes(filename, attrs);
  
  	}
docs: Change the permissions of a file.
  
  @param filename
  the path to the file.
  @param permissions
  a string containing the permissions, for example "rw-r--r--"
  
  @throws SftpStatusException
  , SshException