code: private void actionAppend() throws PageException {
  	if (output == null) throw new ApplicationException("attribute output is not defined for tag file");
  	checkFile(pageContext, securityManager, file, serverPassword, createPath, true, false, true);
  
  	setACL(pageContext, file, acl);
  	try {
  	    if (!file.exists()) file.createNewFile();
  	    String content = Caster.toString(output);
  	    if (fixnewline) content = doFixNewLine(content);
  	    if (addnewline) content += SystemUtil.getOSSpecificLineSeparator();
  	    IOUtil.write(file, content, CharsetUtil.toCharset(charset), true);
  
  	}
  	catch (UnsupportedEncodingException e) {
  	    throw new ApplicationException("Unsupported Charset Definition [" + charset + "]", e.getMessage());
  	}
  	catch (IOException e) {
  	    throw new ApplicationException("can't write file", e.getMessage());
  	}
  	setMode(file, mode);
  	setAttributes(file, attributes);
      }
docs: append data to source file
  
  @throws PageException