diff --git a/bin/deduperemoverb b/bin/deduperemoverb
new file mode 100755
index 0000000..ab4fdde
--- /dev/null
+++ b/bin/deduperemoverb
@@ -0,0 +1,51 @@
+#!/usr/bin/env ruby
+# vim: set noet sw=2 ts=2 sts=2:
+
+require 'dencli'
+require 'deduperemoverb'
+require 'ostruct'
+require 'logger'
+
+$logger = Logger.new STDERR
+$logger.formatter =
+	proc do |severity, datetime, progname, message|
+		sprintf "%s %s %s\n", datetime.strftime( '%H:%M:%S.%6N'), severity[0], message
+	end
+
+begin
+	cli = DenCli.new File.basename($0), <<EOF
+Deduplicates extents, which were already registered by `duperemove`.
+This tool does not provide scanning, yet.
+If PATHx given, only extents of files which matches this pattern and equal extents will be deduplicated.  So, non-equal extents of not listed paths will be ignored.
+EOF
+
+	cli.cmd :help, '(Help)', aliases: [nil, '-h', '--help'], &lambda {|cmd=nil|
+		STDERR.puts cli.help(cmd)
+		exit 1
+	}
+
+	cli.cmd( :dedupe, 'deduplicates files', &lambda {|db, *dirs, tempdb: nil|
+		dbfile = Pathname.new db
+		raise DenCli::UsageError, "Argument 0: Database missing: #{dbfile}"  unless dbfile.exist?
+		tempdb ||= Pathname.new("/run/user/#{Process.uid}").join dbfile.basename
+		dr = Duperemove.new dbfile, tempdb
+		dr.run dirs
+		dr.finish
+	}).opt( :tempdb, '--tempdb=FILE', '-t', "Use given [empty] database as temporary database. (default in /run/user/...)")
+
+	cli.call *ARGV
+
+rescue DenCli::UsageError
+	$logger.fatal "#$!"
+
+rescue SystemExit
+	raise
+
+rescue Interrupt
+	$logger.info "was interrupted"
+	exit 1
+
+rescue
+	$logger.fatal "#$! (#{$!.class})\n#{$!.backtrace.join "\n\t"}"
+
+end
diff --git a/bin/deduperemoverb.rb b/bin/deduperemoverb.rb
deleted file mode 100755
index 56018c5..0000000
--- a/bin/deduperemoverb.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-#!/usr/bin/env ruby
-# vim: set noet sw=2 ts=2 sts=2:
-
-require 'deduperemoverb'
-require 'ostruct'
-require 'logger'
-
-$logger = Logger.new STDERR
-$logger.formatter =
-	proc do |severity, datetime, progname, message|
-		sprintf "%s %s %s\n", datetime.strftime( '%H:%M:%S.%6N'), severity[0], message
-	end
-
-begin
-	raise "Argument 0: Database expected"  if ARGV.empty?
-	dbfile = Pathname.new ARGV[0]
-	raise "Argument 0: Database missing: #{dbfile}"  unless dbfile.exist?
-	tempfile = Pathname.new("/run/user/#{Process.uid}").join dbfile.basename
-	dr = Duperemove.new dbfile, tempfile
-	dr.run ARGV[1..-1]
-	dr.finish
-
-rescue SystemExit
-	raise
-
-rescue Interrupt
-	$logger.info "was interrupted"
-	exit 1
-
-rescue
-	$logger.fatal "#$! (#{$!.class})\n#{$!.backtrace.join "\n\t"}"
-
-end
diff --git a/deduperemoverb.gemspec b/deduperemoverb.gemspec
index bb5da2b..81c671e 100644
--- a/deduperemoverb.gemspec
+++ b/deduperemoverb.gemspec
@@ -1,9 +1,10 @@
 # vim: set noet sw=2 ts=2 sts=2:
 require 'rake'
+require_relative 'lib/deduperemoverb/version'
 
 Gem::Specification.new do |s|
 	s.name = 'deduperemoverb'
-	s.version = '0.0.1'
+	s.version = Duperemove::VERSION
 	s.licenses = %w[LGPLv3]
 	s.authors = 'Denis Knauf'
 	s.homepage = 'https://git.denkn.at/deac/deduperemoverb'
@@ -16,12 +17,14 @@ Gem::Specification.new do |s|
 			ext/*/*.c  ext/*/extconf.rb
 		]]
 	s.bindir = %w[bin]
+	s.executables << 'deduperemoverb'
 	s.require_paths = %w[lib]
 	s.extensions = %w[ext/deduperemoverb/extconf.rb]
 
 	s.add_development_dependency "rake", "~> 13"
 	s.add_dependency "ffi", '~> 1.15'
 	s.add_dependency "sqlite3", '~> 1.4'
+	s.add_dependency 'dencli', '~> 0.3.1'
 
 	s.requirements << 'cc'
 	s.requirements << 'ruby-dev'
diff --git a/lib/deduperemoverb/file_dedupe_range.rb b/lib/deduperemoverb/file_dedupe_range.rb
index 81fe83f..c026ae5 100644
--- a/lib/deduperemoverb/file_dedupe_range.rb
+++ b/lib/deduperemoverb/file_dedupe_range.rb
@@ -3,17 +3,19 @@
 require 'ffi'
 require 'pathname'
 
-Errno::Errnos = []
-Errno.constants.
-	map    {|c| Errno.const_get c }.
-	select {|c| c.is_a?( Class) and c.superclass == SystemCallError and c.const_defined?( :Errno) }.
-	each   {|c| Errno::Errnos[c::Errno] = c }
+unless Errno.const_defined? :Errnos
+	Errno::Errnos ||= []
+	Errno.constants.
+		map    {|c| Errno.const_get c }.
+		select {|c| c.is_a?( Class) and c.superclass == SystemCallError and c.const_defined?( :Errno) }.
+		each   {|c| Errno::Errnos[c::Errno] = c }
+end
 
 module FileDedupeRange
 	extend FFI::Library
 	ffi_lib Pathname.new( __FILE__).
-		dirname.
-		join( *w[ext deduperemoverb deduperemoverb.so]).
+		dirname.dirname.dirname.
+		join( *%w[ext deduperemoverb deduperemoverb.so]).
 		expand_path.
 		to_s
 
diff --git a/lib/deduperemoverb/version.rb b/lib/deduperemoverb/version.rb
new file mode 100644
index 0000000..39bfe4c
--- /dev/null
+++ b/lib/deduperemoverb/version.rb
@@ -0,0 +1,3 @@
+class Duperemove
+	VERSION = '0.0.2'
+end