That is, a channel guard is ready if and only if the process at the other end of the channel has output to it and this data has not yet been input by this process.
也就是说，只有在通道另一端的进程已经输出数据，而该数据还没有被进程输入的时候，警卫才就绪。
2
What can you do to guard against typos in XPath element and attribute names (both in your stylesheet and in your input documents)?
在监督XPath元素和属性名称的拼写时(包括样式表中和输入文档中)，您可以做些什么？
3
To guard yourself against XSS attacks, filter your input through the htmlentities() function whenever the value of a variable is printed to the output.