Getting attribute value from XML in bash script with XPath string()

Question

Preamble:
This is not a duplicate since all other topics do not answer my specific issue.
I'm on Xubuntu 18.04
using libxml-xpath-perl 1.42 (if that matters)

Problem:
I have an XML, let's say like so:

<root>
    <level1>
        <somechild foo="bar" />
    </level1>
</root

I want to get the value bar from somechilds attribute foo. However, when I query

FOO=$(xpath -e '/root/level1/somechild/@foo' $XMLFILE)"

in my bash script it returns foo="bar" instead of bar.

I've already researched this issue and found out that I have to do something with string() but I just cannot figure out what the right syntax is for that.

I've tried the string() function in various places but the closest I got to success, so far was

FOO="$(xpath -e 'string(/root/level1/somechild/@foo)' $XMLFILE)"

In this case echo $FOO gives me

Query didn't return a nodeset. Value: bar

Still not what I want but at least no error and the Value is recognized as bar

How do I use this properly?

Cyrus · Accepted Answer · 2018-12-09 18:56:34Z

4

With valid XML:

xpath -e 'string(//root/level1/somechild/@foo)' file.xml 2>/dev/null

or

xmlstarlet select --text --template --copy-of 'string(//root/level1/somechild/@foo)' file.xml

or

xmlstarlet select --text --template --match '//root/level1/somechild' --value-of '@foo' file.xml

Output:

bar

edited Dec 9, 2018 at 18:56

answered Dec 9, 2018 at 18:51

Cyrus

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2 Comments

antimatter Over a year ago

Ok, I find that behaviour of xpath weird but sending the output 2 to /dev/null solves the problem. What is also weired that in commandline xpath -q ... works and there is no error message. However in my bash script xpath -q ... still gives me the error. Whatever...I will go for 2>/dev/null Thanks

Michael Kay Over a year ago

Note that the XPath expression is returning an attribute node, and the way in which an attribute node is presented in the output is up to the calling application. If you want the string value, then the string() function gives you it, but some applications can only handle XPath expressions that return nodes.

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