How do I insert an element directly after another element with XMLStarlet?

With this example XML:

<rootnode>
  <element-a /开发者_如何学编程>
  <element-b />
  <element-d />
  <element-e />
</rootnode>

How do I insert element <element-c/> directly after the element <element-b/> using XMLStarlet?

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xml ed -i (or --insert) will put the it before the node, xml ed -a (or --append) will put it after, so you can use either one of:

xml ed -i /rootnode/element-d -t elem -n element-c -v "" file.xml
xml ed -a /rootnode/element-b -t elem -n element-c -v "" file.xml