Sed:在最后一次出现后追加

Question

假设我有以下类型的文件:

<?xml version="1.0" encoding="utf-8"?>
<preferences>
  <section id="widgets">
    <value id="version" xml:space="preserve">1</value>
  </section>
  <section id="wuid-b2a8e6b8-6619-714e-9cfe-466c27c90902">
    <value id="path to widget data" xml:space="preserve">{Preferences}widgets/opera-adblock-1.3.4-1.oex</value>
  </section>
  <section id="wuid-0c5cfdb2-8e51-f149-a1e7-51d66240ed7a">
    <value id="path to widget data" xml:space="preserve">{Preferences}widgets/flag-button-1.5.4-1.oex</value>
  </section>
</preferences>

我的任务是在最后一次出现 </section> 后立即添加文本。

看看这两个似乎使用 tac 会更简单，但我也不明白如何做到这一点: Using sed to append a string to the fourth occurrence of a pattern , http://www.unix.com/unix-dummies-questions-answers/46294-add-line-after-last-occurnace-pattern.html#post302149709

谢谢。

Answer 1

在字符串第一次出现之前添加内容更容易:

sed '/<\/preferences>/i\ADD SOME TEXT\nADD SOME MORE TEXT' file

结果:

<?xml version="1.0" encoding="utf-8"?>
<preferences>
  <section id="widgets">
    <value id="version" xml:space="preserve">1</value>
  </section>
  <section id="wuid-b2a8e6b8-6619-714e-9cfe-466c27c90902">
    <value id="path to widget data" xml:space="preserve">{Preferences}widgets/opera-adblock-1.3.4-1.oex</value>
  </section>
  <section id="wuid-0c5cfdb2-8e51-f149-a1e7-51d66240ed7a">
    <value id="path to widget data" xml:space="preserve">{Preferences}widgets/flag-button-1.5.4-1.oex</value>
  </section>
ADD SOME TEXT
ADD SOME MORE TEXT
</preferences>

您可以阅读有关如何在字符串 here 之前插入一行的更多信息。哈。