Bash Parse XML to comma separated list

Question

How do I return a comma-separated list of the ids, please?

<nodes>
 <node>
   <id>1</id>
   <name>idbread</name>
 </node>
 <node>
   <id>2</id>
   <name>idbutter</name>
 </node>
</nodes>

expected output

1,2

I attempted to use XPath, but concat returns only the first value.

xpath node.xml "//nodes/node/id/text()" 2>/dev/null

returns

12

Where does that `xpath` binary/script come from? The only one I [found](https://manpages.ubuntu.com/manpages/xenial/en/man1/xpath.1p.html) does not have the syntax you're using. — fredrik, Dec 07 '19 at 21:14
@fredrik: OP is probably doing something like this `xmllint --xpath "//nodes/node/id/text()" node.xml` but on my system it returns `12`. Version: `xmllint: using libxml version 20904` — Arkadiusz Drabczyk, Dec 07 '19 at 21:16
@ArkadiuszDrabczyk how do you come to that conclusion when he states in the question which command he is running? — fredrik, Dec 07 '19 at 21:20
@fredrik: it's just my guess, he might provide only a part of the real command he's using. In any case, he has to make this question more clear to get an answer. — Arkadiusz Drabczyk, Dec 07 '19 at 21:21
@mri.o you could use `echo $(sed -n 's:$.*$:\1, :pg' file)` — builder-7000, Dec 07 '19 at 21:24
@sergio: [Don't Parse XML/HTML With Regex.](https://stackoverflow.com/a/1732454/3776858) I suggest to use an XML/HTML parser (xmlstarlet, xmllint ...). — Cyrus, Dec 07 '19 at 21:36
Hi @fredrik, I am using a Mac, xpath is in it by default, I didn't have to install anything extra to run: xpath node.xml "//nodes/node/id/text()" 2>/dev/null — mr i.o, Dec 07 '19 at 23:46
@sergio, I am trying as much as possible not to use any other external library to do this, I wil accept your suggestion if you post it as an answer. It works great. — mr i.o, Dec 07 '19 at 23:48

zx485 · Answer 1 · 2019-12-07T21:44:59.383

You can use xmlstarlet for this:

xmlstarlet sel -t -v "/nodes/node[1]/id" -m "/nodes/node[position()>1]" -v "concat(',',id)" input.xml

This outputs the value of the first node/id node and then outputs the following node/ids separated by a comma. The output is as desired.

The sel option chooses the Select/Query mode of xmlstarlet
The -t indicates the start of an "XSLT template"
The first -v option outputs the value of the XPath expression
The -m option creates a for-each over the XPath expression
The second -v option outputs the value of the XPath expression relative to the context value of the for-each

score 1 · Accepted Answer · answered Dec 07 '19 at 22:16

1

A simpler option, using xidel which supports xpath 3.0:

xidel -s node.xml -e "string-join(//nodes/node/id/text(),',')"

answered Dec 07 '19 at 22:16

Jack Fleeting

2 Answers2