logmngr: add logread and default uci config

* all logging packages have a custom implmentation for logread,
  which is a command that can be invoked to view the logs. Hence,
  it makes sense for logmngr to have a logread to accompany it
  as well. Support for the same is added via this commit.
* the approach is simplistic and follows syslog-ng with the
  slight enhancement of reading the logfile from logmngr uci
* support to generate default uci config for logmngr which is
  to write logs to /var/log/messages

logmngr/Makefile

@@ -49,10 +49,16 @@ define Build/Compile
 endef
 
 define Package/logmngr/install
-	$(INSTALL_DIR) $(1)/lib/logmngr
 	$(INSTALL_DIR) $(1)/etc/init.d
-
 	$(INSTALL_BIN) ./files/logmngr.init $(1)/etc/init.d/logmngr
+
+	$(INSTALL_DIR) $(1)/usr/sbin
+	$(INSTALL_BIN) ./files/logread $(1)/usr/sbin
+
+	$(INSTALL_DIR) $(1)/etc/uci-defaults
+	$(INSTALL_BIN) ./files/10-logmngr_config_generate $(1)/etc/uci-defaults/
+
+	$(INSTALL_DIR) $(1)/lib/logmngr
 ifeq ($(CONFIG_LOGMNGR_BACKEND_FLUENTBIT),y)
 	$(INSTALL_DATA) ./files/lib/logmngr/fluent-bit.sh $(1)/lib/logmngr/.
 endif

logmngr/files/10-logmngr_config_generate

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+if [ -s "/etc/config/logmngr" ]; then
+	if uci -q get logmngr.@globals[0] >/dev/null; then
+		# return if there is any valid content
+		exit
+	else
+		rm -f /etc/config/logmngr
+	fi
+fi
+touch /etc/config/logmngr
+
+uci set logmngr.globals=globals
+uci set logmngr.globals.enable=1
+
+uci set logmngr.a1=action
+uci set logmngr.a1.name="ac1"
+
+uci set logmngr.lf1=log_file
+uci set logmngr.lf1.enable=1
+uci set logmngr.lf1.action="ac1"
+uci set logmngr.lf1.file="/var/log/messages"

logmngr/files/logread

@@ -0,0 +1,108 @@
+#!/bin/sh
+# Shell script compatibility wrapper for /sbin/logread
+#
+# Copyright (C) 2019 Dirk Brenken <dev@brenken.org>
+#
+# 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; either version 2 of the License, or
+# (at your option) any later version.
+#
+# 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+#
+
+. /lib/functions.sh
+
+# use /var/log/messages as default
+logfile="/var/log/messages"
+
+
+handle_log_file() {
+	local section="$1"
+
+	local enabled
+	config_get enabled $section enable
+	if [ "$enabled" == 0 ]; then
+		return
+	fi
+
+	local file
+	config_get file $section file
+	if [ -z "$file" ]; then
+		return
+	fi
+
+	logfile="$file"
+}
+
+config_load logmngr
+config_get logmngr_enabled globals enable
+if [ "$logmngr_enabled" == "0" ]; then
+	printf "%s\n" "Error: logmngr is not enabled!"
+	exit 2
+fi
+
+# treat the last enabled log_file as logfile
+config_foreach handle_log_file log_file
+
+if [ ! -f "${logfile}" ]
+then
+	printf "%s\n" "Error: logfile $logfile not found!"
+	exit 2
+fi
+
+usage()
+{
+	printf "%s\n" "Usage: logread [options]"
+	printf "%s\n" "Options:"
+	printf "%5s %-10s%s\n" "-l" "<count>" "Got only the last 'count' messages"
+	printf "%5s %-10s%s\n" "-e" "<pattern>" "Filter messages with a regexp"
+	printf "%5s %-10s%s\n" "-f" "" "Follow log messages"
+	printf "%5s %-10s%s\n" "-h" "" "Print this help message"
+}
+
+if [ -z "${1}" ]
+then
+	cat "${logfile}"
+	exit 0
+else
+	while [ "${1}" ]
+	do
+		case "${1}" in
+			-l)
+				shift
+				count="${1//[^0-9]/}"
+				tail -n "${count:-50}" "${logfile}"
+				exit 0
+				;;
+			-e)
+				shift
+				pattern="${1}"
+				grep -E "${pattern}" "${logfile}"
+				exit 0
+				;;
+			-f)
+				tail -f "${logfile}"
+				exit 0
+				;;
+			-fe)
+				shift
+				pattern="${1}"
+				tail -f "${logfile}" | grep -E "${pattern}"
+				exit 0
+				;;
+			-h|*)
+				usage
+				exit 1
+				;;
+		esac
+		shift
+	done
+fi