Building a 'table of contents' - xpath

Question

Consider the following 'sample.xml'
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
<level>
<name>testA</name>
<level>
<name>testB</name>
</level>
<level>
<name>testC</name>
<level>
<name>testD</name>
<level>
<name>testE</name>
</level>
</level>
</level>
</level>
</root>
Using xmlstarlet i can do:
xml sel -t -m //level -v name -o " " -v "count(ancestor::*)-1" -o "." -v "count(preceding-sibling::*)" -n sample.xml
This produces:
testA 0.0
testB 1.1
testC 1.2
testD 2.1
testE 3.1
What should i do to get:
testA 0.0
testB 1.1
testC 1.2
testD 1.2.1
testE 1.2.1.1
In this example i only have 4 levels, but this can be more than 4.
I am thinking of some kind of recursion, are there any links available which can explain how to do that?

Answer 1

You should be able to do this using XSLT with the "tr" command in xmlstarlet...
However your desired output is a little confusing. If "testA" is the first level and you start at zero, why don't all the other entries start at zero? Or maybe "root" is supposed to be zero?
Anyway, here's an example that starts at 1 instead of zero that should get you started...
XML Input (input.xml)
<root>
<level>
<name>testA</name>
<level>
<name>testB</name>
</level>
<level>
<name>testC</name>
<level>
<name>testD</name>
<level>
<name>testE</name>
</level>
</level>
</level>
</level>
</root>
XSLT 1.0 (test.xsl)
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:strip-space elements="*"/>
<xsl:template match="level">
<xsl:value-of select="concat(name, ' ')"/>
<xsl:for-each select="ancestor-or-self::level">
<xsl:if test="not(position()=1)">.</xsl:if>
<xsl:number/>
</xsl:for-each>
<xsl:text>
</xsl:text>
<xsl:apply-templates select="level"/>
</xsl:template>
</xsl:stylesheet>
Command Line
xmlstarlet tr test.xsl input.xml
Output
testA 1
testB 1.1
testC 1.2
testD 1.2.1
testE 1.2.1.1

Answer 2

This problem can be solved without recursion, by iterating over
elements on the ancestor-or-self axis.
The following xmlstarlet command processes all level elements using
the inner -m (xsl:for-each) to handle each path from root to target
(as suggested in comments the shell variable base defaults to 0 but
can be set to 1).
xmlstarlet select -T -t \
-m '//level' \
-v 'concat(name," ")' \
-m 'ancestor-or-self::level' \
--if 'position() = 1' \
-v "'${base:-0}'" \
--else \
-o '.' \
-v 'count(preceding-sibling::level) + 1' \
-b \
-b \
-n \
file.xml
Output:
testA 0
testB 0.1
testC 0.2
testD 0.2.1
testE 0.2.1.1
For a more compact inner -m -- producing the same output -- instead
-m 'ancestor-or-self::level' \
--if 'position() != 1' -o '.' -b \
-v 'count(preceding-sibling::level) + number(position() != 1)' \
-b \
where the count is incremented by 1 for all except the root level
where position() is 1.
As a variation on the same theme: select elements with the shell
variable target and print their paths as XPath expressions using the
XSLT current() function to reference the
element being processed by the inner -m:
target='//level[name="testB" or name="testE"]'
xmlstarlet select -T -t \
-m "${target}" \
-m 'ancestor-or-self::*' \
--var pos='1 + count(preceding-sibling::*[name() = name(current())])' \
-v 'concat("/",name(),"[",$pos,"]")' \
-b \
-n \
file.xml
Output:
/root[1]/level[1]/level[1]
/root[1]/level[1]/level[2]/level[1]/level[1]