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Searching and replacing a block of XML formatted text in Bash

I have been trying to figure out how to search a block of XML formatted text and modify it in Bash. The file I want to process is a simulation file with XML fomatting. Assume that the file contains multiple blocks of XML stataments as:

<mote>
  <breakpoints />
  <interface_config>
    org.contikios.cooja.interfaces.Position
    <x>0.0</x>
    <y>75.0</y>
    <z>0.0</z>
  </interface_config>
  <interface_config>
    org.contikios.cooja.mspmote.interfaces.MspClock
    <deviation>1.0</deviation>
  </interface_config>
  <interface_config>
    org.contikios.cooja.mspmote.interfaces.MspMoteID
    <id>4</id>
  </interface_config>
  <motetype_identifier>sky2</motetype_identifier>
</mote>

What I want to search is a block of XML statements here:

<id>4</id>
  </interface_config>
  <motetype_identifier>sky2</motetype_identifier>

And replace it with

<id>4</id>
  </interface_config>
  <motetype_identifier>sky3</motetype_identifier>

Rest of the XML statements before and after these statements will remain unchanged. This will enable me to change the mote type Node 4 from sky2 to sky3 in a script in Bash.

Solution 
  • xmlstarlet ed --omit-decl -u "//mote[interface_config/id='4']/motetype_identifier" -v 'sky3' file.xml

    Output:

    <mote>
  <breakpoints/>
  <interface_config>
    org.contikios.cooja.interfaces.Position
    <x>0.0</x>
    <y>75.0</y>
    <z>0.0</z>
  </interface_config>
  <interface_config>
    org.contikios.cooja.mspmote.interfaces.MspClock
    <deviation>1.0</deviation>
  </interface_config>
  <interface_config>
    org.contikios.cooja.mspmote.interfaces.MspMoteID
    <id>4</id>
  </interface_config>
  <motetype_identifier>sky3</motetype_identifier>
</mote>

    If you want to edit file.xml inplace, add option -L.

    See: xmlstarlet ed --help