--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/relpipe-data/examples/relpipe-in-sparql.sh	Mon Jul 27 17:51:53 2020 +0200
@@ -0,0 +1,86 @@
+#!/bin/bash
+
+# Relational pipes
+# Copyright © 2020 František Kučera (Frantovo.cz, GlobalCode.info)
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 of the License.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+relpipe_in_sparql_help() {
+	cat <<-EOF
+		SPARQL query is expected on the STDIN. Exapmple:
+		  echo 'SELECT * WHERE { ?subject ?predicate ?object . } LIMIT 3' \
+| relpipe-in-sparql | relpipe-out-tabular
+		
+		Namespace prefixes are part of the query.
+		But because they are usually constant, they can be set as the 
+		RELPIPE_IN_SPARQL_PREFIXES environmental variable.
+		Then they are prepended to the query.
+		
+		SPARQL endpoint can be set ad-hoc by the --endpoint option.
+		
+		To configure default SPARQL endpoint, add something like this to your environment:
+		  export RELPIPE_IN_SPARQL_ENDPOINT="https://query.wikidata.org/sparql"
+		  export RELPIPE_IN_SPARQL_ENDPOINT="https://dbpedia.org/sparql"
+		  export RELPIPE_IN_SPARQL_ENDPOINT="https://data.gov.cz/sparql"
+		  export RELPIPE_IN_SPARQL_ENDPOINT="https://data.cssz.cz/sparql"
+
+		The relation name defaults to "rdf". Custom name can be set using the --relation option.
+EOF
+}
+
+relation="rdf";
+endpoint="${RELPIPE_IN_SPARQL_ENDPOINT:-https://dbpedia.org/sparql}";
+
+while [[ $# -gt 0 ]]; do
+	argument="$1";
+	case "$argument" in
+		"--relation") relation="$2"; shift; shift; ;;
+		"--endpoint") endpoint="$2"; shift; shift; ;;
+		"--help") relpipe_in_sparql_help; exit; ;;
+	esac
+done
+
+[[ -n "$RELPIPE_IN_SPARQL_PREFIXES" ]] && query="$RELPIPE_IN_SPARQL_PREFIXES"; query+=$'\n\n';
+
+query+="$(</dev/stdin)";
+
+
+# Simple implementation that utilizes the CSV output of the SPARQL endpoint.
+relpipe_in_sparql_implementation_csv() {
+	curl \
+		--header "Accept: text/csv" \
+		--data-urlencode query="$query" \
+		--fail \
+		--silent \
+		--show-error \
+		"$endpoint" \
+		| relpipe-in-csv "$relation"
+}
+
+# More powerful implementation based on XML.
+# Can be customized through XSLT.
+# But: has more dependencies and avoids streaming.
+relpipe_in_sparql_implementation_xml() {
+	DIR="$(dirname $(realpath "$0"))";
+	curl \
+		--header "Accept: application/sparql-results+xml" \
+		--data-urlencode query="$query" \
+		--fail \
+		--silent \
+		--show-error \
+		"$endpoint" \
+		| xsltproc --stringparam "relation" "$relation" "$DIR/relpipe-in-sparql.xsl" - \
+		| relpipe-in-xml
+}
+
+relpipe_in_sparql_implementation_${RELPIPE_IN_SPARQL_IMPLEMENTATION:-csv}