Updating an existing xml file elements using xmlstarlet

Question

I have the following xml file:

<?xml version="1.0" encoding="UTF-8"?>
<sec>
  <NewTempP>xxx</NewTempP>
  <fig>
    <label></label>
    <caption>
      <p/>
    </caption>
    <graphic/>
  </fig>
  <NewTempP>aaaa</NewTempP>
  <fig>
    <label></label>
    <caption>
      <p/>
    </caption>
    <graphic/>
  </fig>
  <NewTempP>zzzz</NewTempP>
  <fig>
    <label></label>
    <caption>
      <p/>
    </caption>
    <graphic/>
  </fig>
....
</sec>

I wrote xmlstarlet in a bash script that iterates over each <NewTempP> element in the XML file, checks if it has an immediate following sibling <fig> with a child element <label>, and if so, copies the content of <NewTempP> to the corresponding <label>:

#!/bin/bash

# Path to your XML file
xmlfile="test.xml"

# Iterate over each <NewTempP> element
xmlstarlet sel -t -c "/sec/NewTempP" "$xmlfile" | while read -r newTempP; do
    # Extract the content of <NewTempP>
    content=$(echo "$newTempP" | xmlstarlet sel -t -v ".")

    # Check if there's an immediate following sibling <fig> with a child <label>
    figLabel=$(echo "$newTempP" | xmlstarlet sel -t -v "following-sibling::fig/label")

    if [ -n "$figLabel" ]; then
        # Update the <label> element with the content of <NewTempP>
        xmlstarlet ed - L --inplace -u "following-sibling::fig/label" -v "$content" "$xmlfile"
    fi
done

The script does not update <label> and no any error messages. What is wrong? The result should be:

<?xml version="1.0" encoding="UTF-8"?>
<sec>
  <NewTempP>xxx</NewTempP>
  <fig>
    <label>xxx</label>
    <caption>
      <p/>
    </caption>
    <graphic/>
  </fig>
  <NewTempP>aaaa</NewTempP>
  <fig>
    <label>aaaa</label>
    <caption>
      <p/>
    </caption>
    <graphic/>
  </fig>
  <NewTempP>zzzz</NewTempP>
  <fig>
    <label>zzzz</label>
    <caption>
      <p/>
    </caption>
    <graphic/>
  </fig>
....
</sec>

Thanks in advance.

Ofuuzo

Daniel Haley · Accepted Answer · 2024-04-19 14:36:53Z

0

I think the main issue is you're running two different xmlstarlet commands. When you run your second command and use the xpath following-sibling::fig/label, you've lost the context (following-sibling of what?).

You could do this with just a single xmlstarlet ed command...

command line:

xmlstarlet ed -P -u "//fig[preceding-sibling::*[1][self::NewTempP]]/label" -x "string(../preceding-sibling::NewTempP[1])" test.xml

output:

<?xml version="1.0"?>
<sec>
    <NewTempP>xxx</NewTempP>
    <fig>
        <label>xxx</label>
        <caption>
            <p/>
        </caption>
        <graphic/>
    </fig>
    <NewTempP>aaaa</NewTempP>
    <fig>
        <label>aaaa</label>
        <caption>
            <p/>
        </caption>
        <graphic/>
    </fig>
    <NewTempP>zzzz</NewTempP>
    <fig>
        <label>zzzz</label>
        <caption>
            <p/>
        </caption>
        <graphic/>
    </fig>
    ....
</sec>

edited Apr 19, 2024 at 14:36

answered Apr 19, 2024 at 14:24

Daniel Haley

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