diff --git a/src/coverage/inject/cli.cr b/src/coverage/inject/cli.cr
index 9951535..2d1a53a 100644
--- a/src/coverage/inject/cli.cr
+++ b/src/coverage/inject/cli.cr
@@ -1,31 +1,40 @@
 require "option_parser"
-# require "tempfile"
+require "log"
 
 module Coverage
   module CLI
+    Log = ::Log.for("cli")
+
     def self.run
       output_format = "HtmlReport"
-      filenames = [] of String
+      targets = [] of String
       print_only = false
 
       OptionParser.parse! do |parser|
-        parser.banner = "Usage: crystal-cover [options] <filename>"
+        parser.banner = "Usage: crystal-coverage [options] <directories or filenames>"
+        parser.on("-h", "--help", "show this help") { puts parser; exit }
         parser.on("-o FORMAT", "--output-format=FORMAT", "The output format used (default: HtmlReport): HtmlReport, Coveralls ") { |f| output_format = f }
         parser.on("-p", "--print-only", "output the generated source code") { |_p| print_only = true }
         parser.on("--use-require=REQUIRE", "change the require of cover library in runtime") { |r| Coverage::SourceFile.use_require = r }
         parser.unknown_args do |args|
           args.each do
-            filenames << ARGV.shift
+            targets << ARGV.shift
           end
         end
       end
 
-      raise "You must choose a file to compile" unless filenames.any?
+      Log.error { "You must choose at least one file to compile" } unless targets.any?
 
       Coverage::SourceFile.outputter = "Coverage::Outputter::#{output_format.camelcase}"
 
+      filenames = targets.map do |target|
+        target += "/**/*.cr" if File.directory?(target)
+        Dir[target]
+      end.flatten.uniq!
+
       first = true
       output = String::Builder.new(capacity: 2**18)
+
       filenames.each do |f|
         v = Coverage::SourceFile.new(path: f, source: ::File.read(f))
         output << v.to_covered_source