--- a/bash-completion.sh	Sat Jan 18 16:41:59 2020 +0100
+++ b/bash-completion.sh	Sat Jan 18 20:09:34 2020 +0100
@@ -13,10 +13,6 @@
 # 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_filesystem_scripts() {
-	while read c; do echo ${c:31}; done < <(compgen -c "__relpipe_in_filesystem_script_");
-}
-
 _relpipe_in_filesystem_completion() {
 	local w0 w1 w2
 
@@ -60,7 +56,7 @@
 	elif [[ "$w2" == "--option"        && "x$w0" == "x" ]];    then COMPREPLY=("''")
 	elif [[ "$w1" == "--file"                           ]];    then COMPREPLY=($(compgen -W "${FILE_FIELDS[*]}"  -- "$w0"))
 	elif [[ "$w1" == "--xattr"                          ]];    then COMPREPLY=($(compgen -W "${XATTR_FIELDS[*]}" -- "$w0"))
-	elif [[ "$w1" == "--streamlet"                      ]];    then COMPREPLY=($(compgen -W "$(_relpipe_in_filesystem_scripts)" -- "$w0"))
+	elif [[ "$w1" == "--streamlet"                      ]];    then COMPREPLY=($(while read c; do PATH="$RELPIPE_IN_FILESYSTEM_STREAMLET_PATH" type -P "$c" &>/dev/null && echo "$c"; done < <(PATH="$RELPIPE_IN_FILESYSTEM_STREAMLET_PATH" compgen -A command -- "$w0")))
 	else
 		OPTIONS=(
 			"--relation"

--- a/src/StreamletAttributeFinder.h	Sat Jan 18 16:41:59 2020 +0100
+++ b/src/StreamletAttributeFinder.h	Sat Jan 18 20:09:34 2020 +0100
@@ -43,11 +43,15 @@
 	std::map<int, std::shared_ptr<SubProcess>> subProcesses;
 	std::map<int, std::vector<AttributeMetadata>> cachedMetadata;
 
-	string_t getExecCommand(const RequestedField& field) {
-		// TODO: move to another directory, exec, not script + use custom $PATH with no prefix
-		return SCRIPT_PREFIX + field.name;
+	string_t getStreamletPath() {
+		const char* originalPath = getenv("PATH");
+		const char* streamletPath = getenv("RELPIPE_IN_FILESYSTEM_STREAMLET_PATH");
+
+		if (originalPath && streamletPath) return convertor.from_bytes(std::string(streamletPath) + ":" + originalPath);
+		else if (originalPath) return convertor.from_bytes(std::string(originalPath));
+		else if (streamletPath) return convertor.from_bytes(std::string(streamletPath));
+		else return L"";
 	}
-
 protected:
 
 	void startFile(const fs::path& file, const string& fileRaw, bool exists) override {
@@ -86,7 +90,7 @@
 				return cachedMetadata[field.id];
 			} else {
 
-				std::vector<string_t> commandLine = {getExecCommand(field)};
+				std::vector<string_t> commandLine = {field.name};
 				std::map<string_t, string_t> environment;
 
 				for (auto mn : StreamletMsg::getMessageNames()) {
@@ -94,6 +98,8 @@
 					environment[L"EXEC_MSG_" + std::to_wstring(mn.first)] = mn.second;
 				}
 
+				environment[L"PATH"] = getStreamletPath();
+
 				shared_ptr<SubProcess> subProcess(SubProcess::create(commandLine, environment));
 				subProcesses[field.id] = subProcess;
 

--- a/streamlet-examples/__relpipe_in_filesystem_script_cloc	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,78 +0,0 @@
-#!/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 counts lines of code of given files. It calls the tool cloc.
-#
-# With no options, these attributes are provided: language, code, comment, blank
-# Specific attributes can be selected using options – e.g. --option 'attribute' 'code'
-# or --option "attribute" "total" (sum of code, comment and blank lines, hidden by default).
-#
-# Optional prefix can be added to attribute names: --option 'prefix' 'my_prefix_'
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	clocFields=()
-
-	for (( i=0; i<${#optionNames[@]}; i++)); do
-		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
-			if [[ "${optionValues[$i]}" =~ ^(language|blank|comment|code)$ ]]; then
-				clocFields+=("${optionValues[$i]}");
-			else
-				echo "Unsupported attribute: ${optionValues[$i]}" >&2
-			fi
-		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
-			clocPrefix="${optionValues[$i]}";
-		else
-			echo "Unsupported option: ${optionNames[$i]}" >&2
-		fi
-	done
-
-	if [[ -z "$clocFields" ]]; then
-		clocFields=( "language" "code" "comment" "blank" ); # + "total"
-	fi
-
-	for (( i=0; i<${#clocFields[@]}; i++)); do
-		if [[ "x${clocFields[$i]}" == "xlanguage" ]]; then local type="string"; else local type="integer"; fi
-		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$clocPrefix${clocFields[$i]}}"    "$type"
-	done
-
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	local language files blank comment code total;
-	
-	[[ -d "$currentFile" ]] || read_nullbyte language files blank comment code total < <( cloc "$currentFile" | perl -ne 'if (/(.*?)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/) { print "$1\0$2\0$3\0$4\0$5\0"; print $3 + $4 + $5; print "\0"; }' );
-
-	for (( i=0; i<${#clocFields[@]}; i++)); do
-		value="${!clocFields[$i]}";
-
-		if [[ "x$files" == "x1" ]]; then                                isNull="false";
-		elif [[ "x${clocFields[$i]}" == "xlanguage" ]]; then value="";  isNull="true";
-		else                                                 value="0"; isNull="true"; fi
-
-		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
-	done
-	
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_exiftool	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,84 +0,0 @@
-#!/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 various file metadata like EXIF or PDF. It calls the tool exiftool.
-# With no options it returns "File:MIMEType" and "exiftool_xml" attributes.
-# Specific attributes can be selected using options – e.g. --option 'attribute' '…'
-# List of available attributes can be obtained by directly calling the "exiftool -X" command on given file or from the "available_attributes" attribute.
-# Two additional attributes are provided by this streamlet:
-#  - "exiftool_xml" – all attributes provided by exiftool in form of XML
-#  - "available_attributes" – list of available attributes (each file may have different) separated by line-breaks (TODO: return as an array of strings, when this data type is implemented)
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	streamletFields=()
-
-	for (( i=0; i<${#optionNames[@]}; i++)); do
-		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
-			streamletFields+=("${optionValues[$i]}");
-		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
-			pdfPrefix="${optionValues[$i]}";
-		else
-			echo "Unsupported option: ${optionNames[$i]}" >&2
-		fi
-	done
-
-	if [[ -z "$streamletFields" ]]; then
-		streamletFields=( "File:MIMEType" "exiftool_xml" );
-	fi
-
-	for (( i=0; i<${#streamletFields[@]}; i++)); do
-		# TODO: data type mappings (integers, booleans)
-		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$pdfPrefix${streamletFields[$i]}}"    "string"
-	done
-
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	local streamletInfo streamletValid value isNull;
-
-	[[ -d "$currentFile" ]] || streamletInfo="$(exiftool -X "$currentFile")";
-	streamletValid="$?";
-
-	for (( i=0; i<${#streamletFields[@]}; i++)); do
-		if   [[ "x${streamletFields[$i]}" == "xexiftool_xml"  ]]; then value="$streamletInfo";
-		elif [[ "x${streamletFields[$i]}" == "xavailable_attributes"  ]]; then
-			value=$'available_attributes\nexiftool_xml\n'"$(echo "$streamletInfo" | relpipe-in-xmltable --relation exif --records '/*/*/*' --attribute 'name' string 'name()' | relpipe-out-nullbyte | tr \\0 \\n)";
-		else
-			value="$(echo "$streamletInfo" | relpipe-in-xmltable --relation exif --records "/*/*/*[name() = '${streamletFields[$i]}']" --attribute 'value' string '.' | relpipe-out-nullbyte | tr -d \\0)";
-			# TODO: parse the XML only once
-			# TODO: validate parameter or use parametrized XPath
-			# TODO: use real namespaces
-		fi
-
-		# n.b. for some files exiftools returns exit code, however it provides some basic properties like file timestamps and <ExifTool:Error>Unknown file type</ExifTool:Error> which is also valid XML and might be useful
-		if   [[ ! "x$streamletValid" == "x0" ]] && [[ "x$value" == "x" ]]; then value="";  isNull="true";
-		else                                                                               isNull="false";
-		fi
-
-		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
-	done
-	
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_exiv2	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,80 +0,0 @@
-#!/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 EXIF metadata. It calls the tool exiv2.
-# With no options it returns "Image size", "Copyright" and "Exif comment" attributes.
-# Specific attributes can be selected using options – e.g. --option 'attribute' 'Image size'
-# List of available attributes can be obtained by directly calling the exiv2 command on a image file.
-# Two additional attributes are provided by this streamlet: "Image height" and "Image width" (they are extracted from "Image size").
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	streamletFields=()
-
-	for (( i=0; i<${#optionNames[@]}; i++)); do
-		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
-			streamletFields+=("${optionValues[$i]}");
-		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
-			pdfPrefix="${optionValues[$i]}";
-		else
-			echo "Unsupported option: ${optionNames[$i]}" >&2
-		fi
-	done
-
-	if [[ -z "$streamletFields" ]]; then
-		streamletFields=( "Image size" "Copyright" "Exif comment" );
-	fi
-
-	for (( i=0; i<${#streamletFields[@]}; i++)); do
-		if [[ "x${streamletFields[$i]}" == "xImage height" ]] ||[[ "x${streamletFields[$i]}" == "xImage width" ]]; then local type="integer"; else local type="string"; fi
-		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$pdfPrefix${streamletFields[$i]}}"    "$type"
-	done
-
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	local streamletInfo streamletValid value isNull;
-
-	[[ -d "$currentFile" ]] || streamletInfo="$(exiv2 "$currentFile")";
-	streamletValid="$?";
-
-	for (( i=0; i<${#streamletFields[@]}; i++)); do
-		value="$(echo "$streamletInfo" | grep -P "^\Q${streamletFields[$i]}\E\s*:" | sed -E 's/[^:]+:\s+(.*)/\1/g' | tr -d '\n';)"; # the field name must not contain "\E"
-
-		if   [[ -z "$value" ]] && [[ "x${streamletFields[$i]}" == "xImage width"  ]]; then value="$(echo "$streamletInfo" | grep -E 'Image size\s*:\s*[0-9]+ x [0-9]+' | sed -E 's/Image size\s*:\s*([0-9]+) x ([0-9]+)/\1/g')";
-		elif [[ -z "$value" ]] && [[ "x${streamletFields[$i]}" == "xImage height" ]]; then value="$(echo "$streamletInfo" | grep -E 'Image size\s*:\s*[0-9]+ x [0-9]+' | sed -E 's/Image size\s*:\s*([0-9]+) x ([0-9]+)/\2/g')";
-		fi
-
-		# n.b. if file has no exif data, exiv2 exits with error „No Exif data found in the file“ and thus $streamletValid != 0, but there still might be some value like „Image size“
-		if   [[ ! "x$streamletValid" == "x0" ]] && [[ "x$value" == "x" ]]; then value="";  isNull="true";
-		else                                                                               isNull="false";
-		fi
-
-		if ( [[ "x${streamletFields[$i]}" == "xImage height" ]] || [[ "x${streamletFields[$i]}" == "xImage width" ]] ) && [[ ! "$value" =~ ^[0-9]+$ ]]; then value="0"; isNull="true"; fi
-
-		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
-	done
-	
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_hash	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,75 +0,0 @@
-#!/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 computes hashes of given files.
-# Default algorithm is sha256.
-#
-# Any supported hash algorithm can be specified by e.g. --option "attribute" "sha512"
-# The hash command is derived from the algorithm name by adding "sum" suffix and must be available at $PATH.
-#
-# Multiple algorithms can be specified (just repeat the --option).
-# But single streamlet instance will run them sequentially.
-# When parallell processing is needed (usually faster) then multiple scriptlet instances should be used:
-#   --scriptlet hash --option "sha1" --as "sha1" --scriptlet hash --option "sha256" --as "sha256"
-# instead of:
-#   --scriptlet hash --option "sha1" --as "sha1" --option "sha256" --as "sha256"
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	hashTypes=()
-	hashCommands=()
-
-	for (( i=0; i<${#optionNames[@]}; i++)); do
-		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
-			if type "${optionValues[$i]}sum" > /dev/null; then
-				hashTypes+=("${optionValues[$i]}");
-				hashCommands+=("${optionValues[$i]}sum");
-			else
-				echo "Unsupported attribute: ${optionValues[$i]}" >&2
-			fi
-		else
-			echo "Unsupported option: ${optionNames[$i]}" >&2
-		fi
-	done
-
-	if [[ -z "$hashTypes" ]]; then
-		hashTypes=("sha256")
-		hashCommands=("sha256sum")
-	fi
-
-	for (( i=0; i<${#hashTypes[@]}; i++)); do
-		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-${hashTypes[$i]}}"    "string"
-	done
-
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	for (( i=0; i<${#hashTypes[@]}; i++)); do
-		value=$("${hashCommands[$i]}" "$currentFile" | cut -d" " -f1) 2>/dev/null;
-		if [[ -z "$value" ]]; then isNull="true"; else isNull="false"; fi
-		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
-	done
-	
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_inode	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,36 +0,0 @@
-#!/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: inode number of given file
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-inode}"    "integer"
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	value=$(ls -d -i "$currentFile" | cut -d" " -f1);
-	send OUTPUT_ATTRIBUTE "$value"    "false";
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_lines_count	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,45 +0,0 @@
-#!/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

--- a/streamlet-examples/__relpipe_in_filesystem_script_mime_type	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,37 +0,0 @@
-#!/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: MIME type of given file.
-# It calls the tool file.
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-mime_type}"    "string"
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	value=$(file --preserve-date --brief --mime-type --dereference "$currentFile");
-	send OUTPUT_ATTRIBUTE "$value"    "false";
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_pdfinfo	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,73 +0,0 @@
-#!/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 PDF metadata of given files. It calls the tool pdfinfo.
-# With no options it returns just number of pages (or 0 if the file is not a PDF).
-# Specific attributes can be selected using options – e.g. --option 'attribute' 'Author'
-# List of available attributes can be obtained by directly calling the pdfinfo command on a PDF file.
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	pdfFields=()
-
-	for (( i=0; i<${#optionNames[@]}; i++)); do
-		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
-			pdfFields+=("${optionValues[$i]}");
-		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
-			pdfPrefix="${optionValues[$i]}";
-		else
-			echo "Unsupported option: ${optionNames[$i]}" >&2
-		fi
-	done
-
-	if [[ -z "$pdfFields" ]]; then
-		pdfFields=( "Pages" );
-	fi
-
-	for (( i=0; i<${#pdfFields[@]}; i++)); do
-		if [[ "x${pdfFields[$i]}" == "xPages" ]]; then local type="integer"; else local type="string"; fi
-		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$pdfPrefix${pdfFields[$i]}}"    "$type"
-	done
-
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	local pdfInfo pdfValid value isNull;
-
-	[[ -d "$currentFile" ]] || pdfInfo="$(pdfinfo -isodates "$currentFile")";
-	pdfValid="$?";
-
-	for (( i=0; i<${#pdfFields[@]}; i++)); do
-		value="$(echo "$pdfInfo" | grep -P "^\Q${pdfFields[$i]}\E:" | sed -E 's/[^:]+:\s+(.*)/\1/g' | tr -d '\n';)"; # the field name must not contain "\E"
-
-		if  ([[ ! "x$pdfValid" == "x0" ]] || [[ "x$value" == "x" ]]) && [[ "x${pdfFields[$i]}" == "xPages" ]]; then value="0"; isNull="true";
-		elif [[ ! "x$pdfValid" == "x0" ]];                                                                     then value="";  isNull="true";
-		else                                                                                                                   isNull="false";
-		fi
-
-		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
-	done
-	
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- a/streamlet-examples/__relpipe_in_filesystem_script_pdftotext	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,38 +0,0 @@
-#!/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

--- a/streamlet-examples/__relpipe_in_filesystem_script_tesseract	Sat Jan 18 16:41:59 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,48 +0,0 @@
-#!/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: OCR recognized texf of given image file. It calls the tool tesseract.
-# Languages can be specified by: --option "language" "eng" --option "language" "ces"
-
-
-. "$(dirname $0)/streamlet-common.sh"
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
-	tesseractLanguage="";
-	for (( i=0; i<${#optionNames[@]}; i++)); do
-		if [[ "x${optionNames[$i]}" == "xlanguage" ]]; then
-			tesseractLanguage+="+${optionValues[$i]}";
-		else
-			echo "Unsupported option: ${optionNames[$i]}" >&2
-		fi
-	done
-
-	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-tesseract}"    "string"
-	send WAITING_FOR_INPUT_ATTRIBUTES
-}
-
-processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
-	value="$(cat "$currentFile" | tesseract stdin stdout "${tesseractLanguage:+-l}" "${tesseractLanguage}")";
-	if   [[ "x$?" == "x0" ]]; then isNull="false"; else value=""; isNull="true"; fi
-	value="$(echo "$value" | tr -d \\f)"
-	send OUTPUT_ATTRIBUTE "$value"    "$isNull";
-	send WAITING_FOR_INPUT_ATTRIBUTES;
-}
-
-initialize
-processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/cloc	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,78 @@
+#!/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 counts lines of code of given files. It calls the tool cloc.
+#
+# With no options, these attributes are provided: language, code, comment, blank
+# Specific attributes can be selected using options – e.g. --option 'attribute' 'code'
+# or --option "attribute" "total" (sum of code, comment and blank lines, hidden by default).
+#
+# Optional prefix can be added to attribute names: --option 'prefix' 'my_prefix_'
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	clocFields=()
+
+	for (( i=0; i<${#optionNames[@]}; i++)); do
+		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
+			if [[ "${optionValues[$i]}" =~ ^(language|blank|comment|code)$ ]]; then
+				clocFields+=("${optionValues[$i]}");
+			else
+				echo "Unsupported attribute: ${optionValues[$i]}" >&2
+			fi
+		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
+			clocPrefix="${optionValues[$i]}";
+		else
+			echo "Unsupported option: ${optionNames[$i]}" >&2
+		fi
+	done
+
+	if [[ -z "$clocFields" ]]; then
+		clocFields=( "language" "code" "comment" "blank" ); # + "total"
+	fi
+
+	for (( i=0; i<${#clocFields[@]}; i++)); do
+		if [[ "x${clocFields[$i]}" == "xlanguage" ]]; then local type="string"; else local type="integer"; fi
+		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$clocPrefix${clocFields[$i]}}"    "$type"
+	done
+
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	local language files blank comment code total;
+	
+	[[ -d "$currentFile" ]] || read_nullbyte language files blank comment code total < <( cloc "$currentFile" | perl -ne 'if (/(.*?)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/) { print "$1\0$2\0$3\0$4\0$5\0"; print $3 + $4 + $5; print "\0"; }' );
+
+	for (( i=0; i<${#clocFields[@]}; i++)); do
+		value="${!clocFields[$i]}";
+
+		if [[ "x$files" == "x1" ]]; then                                isNull="false";
+		elif [[ "x${clocFields[$i]}" == "xlanguage" ]]; then value="";  isNull="true";
+		else                                                 value="0"; isNull="true"; fi
+
+		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	done
+	
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/exiftool	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,84 @@
+#!/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 various file metadata like EXIF or PDF. It calls the tool exiftool.
+# With no options it returns "File:MIMEType" and "exiftool_xml" attributes.
+# Specific attributes can be selected using options – e.g. --option 'attribute' '…'
+# List of available attributes can be obtained by directly calling the "exiftool -X" command on given file or from the "available_attributes" attribute.
+# Two additional attributes are provided by this streamlet:
+#  - "exiftool_xml" – all attributes provided by exiftool in form of XML
+#  - "available_attributes" – list of available attributes (each file may have different) separated by line-breaks (TODO: return as an array of strings, when this data type is implemented)
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	streamletFields=()
+
+	for (( i=0; i<${#optionNames[@]}; i++)); do
+		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
+			streamletFields+=("${optionValues[$i]}");
+		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
+			pdfPrefix="${optionValues[$i]}";
+		else
+			echo "Unsupported option: ${optionNames[$i]}" >&2
+		fi
+	done
+
+	if [[ -z "$streamletFields" ]]; then
+		streamletFields=( "File:MIMEType" "exiftool_xml" );
+	fi
+
+	for (( i=0; i<${#streamletFields[@]}; i++)); do
+		# TODO: data type mappings (integers, booleans)
+		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$pdfPrefix${streamletFields[$i]}}"    "string"
+	done
+
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	local streamletInfo streamletValid value isNull;
+
+	[[ -d "$currentFile" ]] || streamletInfo="$(exiftool -X "$currentFile")";
+	streamletValid="$?";
+
+	for (( i=0; i<${#streamletFields[@]}; i++)); do
+		if   [[ "x${streamletFields[$i]}" == "xexiftool_xml"  ]]; then value="$streamletInfo";
+		elif [[ "x${streamletFields[$i]}" == "xavailable_attributes"  ]]; then
+			value=$'available_attributes\nexiftool_xml\n'"$(echo "$streamletInfo" | relpipe-in-xmltable --relation exif --records '/*/*/*' --attribute 'name' string 'name()' | relpipe-out-nullbyte | tr \\0 \\n)";
+		else
+			value="$(echo "$streamletInfo" | relpipe-in-xmltable --relation exif --records "/*/*/*[name() = '${streamletFields[$i]}']" --attribute 'value' string '.' | relpipe-out-nullbyte | tr -d \\0)";
+			# TODO: parse the XML only once
+			# TODO: validate parameter or use parametrized XPath
+			# TODO: use real namespaces
+		fi
+
+		# n.b. for some files exiftools returns exit code, however it provides some basic properties like file timestamps and <ExifTool:Error>Unknown file type</ExifTool:Error> which is also valid XML and might be useful
+		if   [[ ! "x$streamletValid" == "x0" ]] && [[ "x$value" == "x" ]]; then value="";  isNull="true";
+		else                                                                               isNull="false";
+		fi
+
+		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	done
+	
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/exiv2	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,80 @@
+#!/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 EXIF metadata. It calls the tool exiv2.
+# With no options it returns "Image size", "Copyright" and "Exif comment" attributes.
+# Specific attributes can be selected using options – e.g. --option 'attribute' 'Image size'
+# List of available attributes can be obtained by directly calling the exiv2 command on a image file.
+# Two additional attributes are provided by this streamlet: "Image height" and "Image width" (they are extracted from "Image size").
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	streamletFields=()
+
+	for (( i=0; i<${#optionNames[@]}; i++)); do
+		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
+			streamletFields+=("${optionValues[$i]}");
+		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
+			pdfPrefix="${optionValues[$i]}";
+		else
+			echo "Unsupported option: ${optionNames[$i]}" >&2
+		fi
+	done
+
+	if [[ -z "$streamletFields" ]]; then
+		streamletFields=( "Image size" "Copyright" "Exif comment" );
+	fi
+
+	for (( i=0; i<${#streamletFields[@]}; i++)); do
+		if [[ "x${streamletFields[$i]}" == "xImage height" ]] ||[[ "x${streamletFields[$i]}" == "xImage width" ]]; then local type="integer"; else local type="string"; fi
+		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$pdfPrefix${streamletFields[$i]}}"    "$type"
+	done
+
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	local streamletInfo streamletValid value isNull;
+
+	[[ -d "$currentFile" ]] || streamletInfo="$(exiv2 "$currentFile")";
+	streamletValid="$?";
+
+	for (( i=0; i<${#streamletFields[@]}; i++)); do
+		value="$(echo "$streamletInfo" | grep -P "^\Q${streamletFields[$i]}\E\s*:" | sed -E 's/[^:]+:\s+(.*)/\1/g' | tr -d '\n';)"; # the field name must not contain "\E"
+
+		if   [[ -z "$value" ]] && [[ "x${streamletFields[$i]}" == "xImage width"  ]]; then value="$(echo "$streamletInfo" | grep -E 'Image size\s*:\s*[0-9]+ x [0-9]+' | sed -E 's/Image size\s*:\s*([0-9]+) x ([0-9]+)/\1/g')";
+		elif [[ -z "$value" ]] && [[ "x${streamletFields[$i]}" == "xImage height" ]]; then value="$(echo "$streamletInfo" | grep -E 'Image size\s*:\s*[0-9]+ x [0-9]+' | sed -E 's/Image size\s*:\s*([0-9]+) x ([0-9]+)/\2/g')";
+		fi
+
+		# n.b. if file has no exif data, exiv2 exits with error „No Exif data found in the file“ and thus $streamletValid != 0, but there still might be some value like „Image size“
+		if   [[ ! "x$streamletValid" == "x0" ]] && [[ "x$value" == "x" ]]; then value="";  isNull="true";
+		else                                                                               isNull="false";
+		fi
+
+		if ( [[ "x${streamletFields[$i]}" == "xImage height" ]] || [[ "x${streamletFields[$i]}" == "xImage width" ]] ) && [[ ! "$value" =~ ^[0-9]+$ ]]; then value="0"; isNull="true"; fi
+
+		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	done
+	
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/hash	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,75 @@
+#!/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 computes hashes of given files.
+# Default algorithm is sha256.
+#
+# Any supported hash algorithm can be specified by e.g. --option "attribute" "sha512"
+# The hash command is derived from the algorithm name by adding "sum" suffix and must be available at $PATH.
+#
+# Multiple algorithms can be specified (just repeat the --option).
+# But single streamlet instance will run them sequentially.
+# When parallell processing is needed (usually faster) then multiple scriptlet instances should be used:
+#   --scriptlet hash --option "sha1" --as "sha1" --scriptlet hash --option "sha256" --as "sha256"
+# instead of:
+#   --scriptlet hash --option "sha1" --as "sha1" --option "sha256" --as "sha256"
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	hashTypes=()
+	hashCommands=()
+
+	for (( i=0; i<${#optionNames[@]}; i++)); do
+		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
+			if type "${optionValues[$i]}sum" > /dev/null; then
+				hashTypes+=("${optionValues[$i]}");
+				hashCommands+=("${optionValues[$i]}sum");
+			else
+				echo "Unsupported attribute: ${optionValues[$i]}" >&2
+			fi
+		else
+			echo "Unsupported option: ${optionNames[$i]}" >&2
+		fi
+	done
+
+	if [[ -z "$hashTypes" ]]; then
+		hashTypes=("sha256")
+		hashCommands=("sha256sum")
+	fi
+
+	for (( i=0; i<${#hashTypes[@]}; i++)); do
+		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-${hashTypes[$i]}}"    "string"
+	done
+
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	for (( i=0; i<${#hashTypes[@]}; i++)); do
+		value=$("${hashCommands[$i]}" "$currentFile" | cut -d" " -f1) 2>/dev/null;
+		if [[ -z "$value" ]]; then isNull="true"; else isNull="false"; fi
+		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	done
+	
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/inode	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,36 @@
+#!/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: inode number of given file
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-inode}"    "integer"
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	value=$(ls -d -i "$currentFile" | cut -d" " -f1);
+	send OUTPUT_ATTRIBUTE "$value"    "false";
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /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

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/mime_type	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,37 @@
+#!/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: MIME type of given file.
+# It calls the tool file.
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-mime_type}"    "string"
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	value=$(file --preserve-date --brief --mime-type --dereference "$currentFile");
+	send OUTPUT_ATTRIBUTE "$value"    "false";
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/pdfinfo	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,73 @@
+#!/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 PDF metadata of given files. It calls the tool pdfinfo.
+# With no options it returns just number of pages (or 0 if the file is not a PDF).
+# Specific attributes can be selected using options – e.g. --option 'attribute' 'Author'
+# List of available attributes can be obtained by directly calling the pdfinfo command on a PDF file.
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	pdfFields=()
+
+	for (( i=0; i<${#optionNames[@]}; i++)); do
+		if [[ "x${optionNames[$i]}" == "xattribute" ]]; then
+			pdfFields+=("${optionValues[$i]}");
+		elif [[ "x${optionNames[$i]}" == "xprefix" ]]; then
+			pdfPrefix="${optionValues[$i]}";
+		else
+			echo "Unsupported option: ${optionNames[$i]}" >&2
+		fi
+	done
+
+	if [[ -z "$pdfFields" ]]; then
+		pdfFields=( "Pages" );
+	fi
+
+	for (( i=0; i<${#pdfFields[@]}; i++)); do
+		if [[ "x${pdfFields[$i]}" == "xPages" ]]; then local type="integer"; else local type="string"; fi
+		send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[$i]-$pdfPrefix${pdfFields[$i]}}"    "$type"
+	done
+
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	local pdfInfo pdfValid value isNull;
+
+	[[ -d "$currentFile" ]] || pdfInfo="$(pdfinfo -isodates "$currentFile")";
+	pdfValid="$?";
+
+	for (( i=0; i<${#pdfFields[@]}; i++)); do
+		value="$(echo "$pdfInfo" | grep -P "^\Q${pdfFields[$i]}\E:" | sed -E 's/[^:]+:\s+(.*)/\1/g' | tr -d '\n';)"; # the field name must not contain "\E"
+
+		if  ([[ ! "x$pdfValid" == "x0" ]] || [[ "x$value" == "x" ]]) && [[ "x${pdfFields[$i]}" == "xPages" ]]; then value="0"; isNull="true";
+		elif [[ ! "x$pdfValid" == "x0" ]];                                                                     then value="";  isNull="true";
+		else                                                                                                                   isNull="false";
+		fi
+
+		send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	done
+	
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/pdftotext	Sat Jan 18 20:09:34 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

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/streamlet-examples/tesseract	Sat Jan 18 20:09:34 2020 +0100
@@ -0,0 +1,48 @@
+#!/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: OCR recognized texf of given image file. It calls the tool tesseract.
+# Languages can be specified by: --option "language" "eng" --option "language" "ces"
+
+
+. "$(dirname $0)/streamlet-common.sh"
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES_METADATA() {
+	tesseractLanguage="";
+	for (( i=0; i<${#optionNames[@]}; i++)); do
+		if [[ "x${optionNames[$i]}" == "xlanguage" ]]; then
+			tesseractLanguage+="+${optionValues[$i]}";
+		else
+			echo "Unsupported option: ${optionNames[$i]}" >&2
+		fi
+	done
+
+	send OUTPUT_ATTRIBUTE_METADATA "${outputAttributeAliases[0]-tesseract}"    "string"
+	send WAITING_FOR_INPUT_ATTRIBUTES
+}
+
+processMessage_WAITING_FOR_OUTPUT_ATTRIBUTES() {
+	value="$(cat "$currentFile" | tesseract stdin stdout "${tesseractLanguage:+-l}" "${tesseractLanguage}")";
+	if   [[ "x$?" == "x0" ]]; then isNull="false"; else value=""; isNull="true"; fi
+	value="$(echo "$value" | tr -d \\f)"
+	send OUTPUT_ATTRIBUTE "$value"    "$isNull";
+	send WAITING_FOR_INPUT_ATTRIBUTES;
+}
+
+initialize
+processMessages