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+// SPDX-FileCopyrightText: 2022 M. Shulhan <ms@kilabit.info>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+/*
+Command resolver is command line interface (CLI) for DNS and rescached server.
+
+# SYNOPSIS
+
+	resolver [-insecure] [-ns=<dns-URL>] [-server=<rescached-URL>] <command> [args...]
+
+# DESCRIPTION
+
+resolver is a tool to resolve hostname to IP address or to query services
+on hostname by type (MX, SOA, TXT, etc.) using standard DNS protocol with UDP,
+DNS over TLS (DoT), or DNS over HTTPS (DoH).
+
+It is also provide CLI to the rescached server to manage environment, block.d,
+hosts.d, and zone.d; as in the web user interface.
+
+# OPTIONS
+
+The following options affect the command operation.
+
+	-insecure
+
+Ignore invalid server certificate when querying DoT, DoH, or rescached
+server.
+This option only affect the `query` command.
+
+	-ns=<dns-URL>
+
+This option define the parent DNS server where the resolver send the query.
+This option only affect the `query` command.
+
+The nameserver is defined in the following format,
+
+	("udp"/"tcp"/"https") "://" (domain / ip-address) [":" port]
+
+Examples,
+
+  - udp://194.233.68.184:53 for querying with UDP,
+  - tcp://194.233.68.184:53 for querying with TCP,
+  - https://194.233.68.184:853 for querying with DNS over TLS (DoT), and
+  - https://kilabit.info/dns-query for querying with DNS over HTTPS (DoH).
+
+Default to one of "nameserver" in `/etc/resolv.conf`.
+
+	-server=<rescached-URL>
+
+Set the rescached HTTP server where commands, except query, will be send.
+The rescached-URL use HTTP scheme:
+
+	("http" / "https") "://" (domain / ip-address) [":" port]
+
+Default to https://127.0.0.1:5380 if its empty.
+
+# COMMANDS
+
+Query the DNS server,
+
+	query <domain / ip-address> [type] [class]
+
+Managing block.d files,
+
+	block.d disable <name>
+	block.d enable <name>
+	block.d update <name>
+
+Managing caches,
+
+	caches
+	caches search <string>
+	caches remove <string>
+
+Managing environment,
+
+	env
+	env update <path-to-file / "-">
+
+Managing hosts.d files,
+
+	hosts.d create <name>
+	hosts.d get <name>
+
+Managing record in hosts.d file,
+
+	hosts.d rr add <name> <domain> <value>
+	hosts.d rr delete <name> <domain>
+
+Managing zone.d files,
+
+	zone.d
+	zone.d create <name>
+	zone.d delete <name>
+
+Managing record in zone.d,
+
+	zone.d rr get <zone>
+	zone.d rr add <zone> <"@" | subdomain> <ttl> <type> <class> <value> ...
+	zone.d rr delete <zone> <"@" | subdomain> <type> <class> <value>
+
+For more information see the manual page for resolver(1) or its HTML page at
+http://127.0.0.1:5380/doc/resolver.html.
+*/
+package main