diff -r dc5c210295d0 -r f466b4c7d9b1 streamlet-examples/lines_count
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/lines_count	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,45 @@
+#!/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/>.
+
+
+# This streamlet provides a single attribute: number of lines of given file
+# Standard wc -l is used to count the lines.
+# Directories are reported a 0 lines and with a null flag (will be supported in further Relational pipes versions).
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-lines_count}"    "integer"
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	if [[ -d "$currentFile" ]]; then
+		value="0";
+		isNull="true";
+	else
+		value=$(wc -l "$currentFile" | cut -d" " -f1);
+		isNull="false";
+	fi
+	
+	send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages