diff -r afbce5b8aabf -r f1bbcf616269 streamlet-examples/__relpipe_in_filesystem_script_pdftotext
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/__relpipe_in_filesystem_script_pdftotext	Fri Jan 17 13:02:27 2020 +0100
@@ -0,0 +1,38 @@
+#!/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: plain text content of given PDF file. It calls the tool pdftotext.
+# n.b. the plain text content must fit into memory and shell variable and command-line argument (it usually will)
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-pdftotext}"    "string"
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	value="$(pdftotext "$currentFile" - | tr -d \\f)"; # tr just removes page breaks
+	if   [[ "x$?" == "x0" ]]; then isNull="false"; else value=""; isNull="true"; fi
+	send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages