たぶん完成

wc.rb

@@ -8,30 +8,25 @@ bytes = 0
 
 options = {}
 OptionParser.new do |opts|
-  opts.on('-l') do
-    options[:lines] = true
-  end
-  opts.on('-w') do
-    options[:words] = true
-  end
-  opts.on('-c') do
-    options[:bytes] = true
-  end
+  opts.on('-l') { options[:lines] = true }
+  opts.on('-w') { options[:words] = true }
+  opts.on('-c') { options[:bytes] = true }
 end.parse!
 
-file_path = ARGV[0]
-if file_path.nil?
-  puts 'ファイルパスがありません。'
+input = if !ARGV.empty?
+          File.read(ARGV[0])
+        elsif !$stdin.tty?
+          $stdin.read
+        else
+          puts 'ファイルパスまたはパイプラインからの入力がありません。'
           exit
         end
 
-File.open(file_path) do |file|
-  file.each_line do |line|
+input.each_line do |line|
   lines += 1
   words += line.split.size
   bytes += line.bytesize
 end
-end
 
 options = { bytes: true, lines: true, words: true } if options.empty?
 result = []
@@ -39,4 +34,5 @@ result << lines if options[:lines]
 result << words if options[:words]
 result << bytes if options[:bytes]
 
-puts "#{result.join(' ')} #{file_path}"
+file_name = ARGV[0]
+puts "#{result.join(' ')} #{file_name}"