Adding an XML attribute in Bash

Question

I have an XML data in the following form:

<string name="app_name">my App</string>
<string name="yes">Yes</string>
<string name="no">No</string>
<string name="done">Done</string>

I'm trying to write a Bash script for converting the XML to something like this:

<string comment="for more see http://www.web.com/test/app_name" name="app_name">my App</string>
<string comment="for more see http://www.web.com/test/yes" name="yes">Yes</string>

I did some search and here's what I have found so far.

The code below is making a replacement is every element:

 sed -i 's/<string/<string comment=\"for more see http:\/\/www\.web\.com\/test\/\"    /g' string.xml

And this expression fetches the name attribute:

Sname=$(sed '/name/s/\(.*name=\)\(.*\)/\2/' string.xml|awk -F\" '{print $2}')

But I have no idea how to merge them.

Ruslan Osmanov · Accepted Answer · 2016-11-02 11:33:07Z

3

It is unsafe to use sed, or awk for XML parsing. These tools are very flexible, but they have no built-in XML parsing features. It is very tedious and impractical to implement an XML parser in sed, or awk. I recommend using an XML parser such as xmlstarlet (which is actually more than a parser).

Example

xmlstarlet ed -a '//string[@name]' -t attr -n comment src.xml | \
  xmlstarlet ed -u '//string/@comment' \
  -x 'concat("see http://www.web.com/test/app_name/", ../@name)' > out.xml

The first xmlstarlet command parses src.xml file, appends an empty comment attribute to all string tags having name attribute (using '//string[@name]' XPath expression). The output of the command is passed to the second command through pipeline (|).

The second command reads XML from the pipeline, and updates the comment attributes with the concat() function which, in particular, concatenates the static string "see http://www.web.com/test/app_name/" with the value of name attribute (../@name stands for "name attribute of the parent node").

The output of the second command is redirected to out.xml file.

Sample Input

<root x="10">
  <string name="app_name">my App</string>
  <string name="yes">Yes</string>
  <string name="no">No</string>
  <string name="done">Done</string>
</root>

Sample Output

<?xml version="1.0"?>
<root x="10">
  <string name="app_name" comment="see http://www.web.com/test/app_name/app_name">my App</string>
  <string name="yes" comment="see http://www.web.com/test/app_name/yes">Yes</string>
  <string name="no" comment="see http://www.web.com/test/app_name/no">No</string>
  <string name="done" comment="see http://www.web.com/test/app_name/done">Done</string>
</root>

edited Nov 2, 2016 at 11:33

answered Oct 28, 2016 at 17:33

Ruslan Osmanov

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2 Comments

user2299735 Over a year ago

hi, Thanks for perfect solution, I changed xml to xmlstarlet and it is working like charm. Can you explain how it works, parameters and explanation if possible for sake of learning

Ruslan Osmanov Over a year ago

@user2299735, added some extra info. Please accept the answer, if you think it fixes your problem.

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