GDAL add custom fields to GPX files using the command line (batch)

Question

Using the GDAL/OGR command line, how could one add some fields to a GPX file ?

I simply need to add the gpx filename to its content, e.g. in a new field called datasource in each (there are several in a file):

<?xml version="1.0"?>
<gpx version="1.1" creator="GDAL 3.4.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ogr="http://osgeo.org/gdal" xmlns="http://www.topografix.com/GPX/1/1" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd">
<metadata><bounds minlat="41.300000000000003" minlon="10.900000000000000" maxlat="69.700000000000000" maxlon="31.000000000000000"/></metadata>                   
<trk>
  <name>001: Test layer 1</name>
  <desc>Layer one</desc>
  <!-- I want to add the following 3 lines: --> 
  <extensions>
    <ogr:datasource>GPX_Filename</ogr:datasource>
  </extensions>
  <trkseg>
    ...
  </trkseg>
</trk>
<trk>
  <name>002 Test layer 2</name>
  <desc>Layer two</desc>
  <!-- I want to add the following 3 lines: --> 
  <extensions>
    <ogr:datasource>GPX_Filename</ogr:datasource>
  </extensions>
  <trkseg>
    ...
  </trkseg>
</trk>
...
</gpx>

How would can I automate this using the command line (on Linux) ?

GDAL version: GDAL 3.4.1, released 2021/12/27

Answer 1

I've implemented a quick workaround in bash, because I wasn't able to figure out a way to directly achieve that using GDAL. It's based on a tool called xmlstarlet which allow to manipulate an XML file using the command line.

#!/bin/bash

for f in *.gpx;
do
  xmlstarlet edit \
    --inplace \
    -N x="http://www.topografix.com/GPX/1/1" \
    --insert "/x:gpx" --type attr -n "xmlns:ogr" -v "http://osgeo.org/gdal" \
    --append "/x:gpx/x:trk/x:desc" --type  elem -n "extensions" \
    --subnode "///extensions" --type elem -n "ogr:datasource" -v "${f%%.*}" \
    "${f}"
done