allow piping of crontab from stdin to stdout

bin/whenever

@@ -33,6 +33,9 @@ OptionParser.new do |opts|
   opts.on('-k', '--cut [lines]', 'Cut lines from the top of the cronfile') do |lines|
     options[:cut] = lines.to_i if lines
   end
+  opts.on('-p', '--pipe', 'Pipe crontab from stdin, through whenever, and out to stdout') do
+    options[:pipe] = true
+  end
   opts.on('-v', '--version') { puts "Whenever v#{Whenever::VERSION}"; exit(0) }
 end.parse!
 

lib/whenever/command_line.rb

@@ -57,32 +57,51 @@ module Whenever
     
     def read_crontab
       return @current_crontab if @current_crontab
-      
-      command = ['crontab -l']
-      command << "-u #{@options[:user]}" if @options[:user]
-      
-      command_results  = %x[#{command.join(' ')} 2> /dev/null]
-      @current_crontab = $?.exitstatus.zero? ? prepare(command_results) : ''
+
+      command_results = (
+        if @options[:pipe]
+          stdin.read
+        else
+          command = ['crontab -l']
+          command << "-u #{@options[:user]}" if @options[:user]
+          
+          result = %x[#{command.join(' ')} 2> /dev/null]
+
+          $?.exitstatus.zero? ? result : ''
+        end
+      )
+
+      @current_crontab = prepare(command_results)
     end
     
     def write_crontab(contents)
-      tmp_cron_file = Tempfile.new('whenever_tmp_cron').path
-      File.open(tmp_cron_file, File::WRONLY | File::APPEND) do |file|
-        file << contents
-      end
+      target_fh = (
+        if @options[:pipe]
+          stdout
+        else
+          File.open(Tempfile.new('whenever_tmp_cron').path, File::WRONLY | File::APPEND)
+        end
+      )
+      
+      target_fh << contents
+      target_fh.close
 
-      command = ['crontab']
-      command << "-u #{@options[:user]}" if @options[:user]
-      command << tmp_cron_file
-
-      if system(command.join(' '))
-        action = 'written' if @options[:write]
-        action = 'updated' if @options[:update]
-        puts "[write] crontab file #{action}"
+      if @options[:pipe]
         exit(0)
       else
-        warn "[fail] Couldn't write crontab; try running `whenever' with no options to ensure your schedule file is valid."
-        exit(1)
+        command = ['crontab']
+        command << "-u #{@options[:user]}" if @options[:user]
+        command << target_file
+
+        if system(command.join(' '))
+          action = 'written' if @options[:write]
+          action = 'updated' if @options[:update]
+          puts "[write] crontab file #{action}"
+          exit(0)
+        else
+          warn "[fail] Couldn't write crontab; try running `whenever' with no options to ensure your schedule file is valid."
+          exit(1)
+        end
       end
     end
     
@@ -129,5 +148,13 @@ module Whenever
     def comment_close
       "# End #{comment_base}"
     end
+    
+    def stdin
+      $stdin
+    end
+
+    def stdout
+      $stdout
+    end
   end
 end

test/functional/command_line_test.rb

@@ -319,4 +319,42 @@ EXISTING_CRON
     end
   end
 
+  context 'A command line update that reads the cron from stdin writes to stdout' do
+    setup do
+      @mock_stdin = StringIO.new(<<-EXISTING_CRON)
+# Something
+
+# Begin Whenever generated tasks for: My identifier
+My whenever job that was already here
+# End Whenever generated tasks for: My identifier
+EXISTING_CRON
+
+      @mock_stdout = StringIO.new
+
+      File.expects(:exists?).with('config/schedule.rb').returns(true)
+      @command = Whenever::CommandLine.new(:update => true, :identifier => 'My identifier', :pipe => true)
+      @task = "#{two_hours} /my/command"
+      Whenever.expects(:cron).returns(@task)
+
+      @command.stubs(:stdin).returns(@mock_stdin)
+      @command.stubs(:stdout).returns(@mock_stdout)
+    end
+
+    should "update the file and write out a new file correctly" do
+      begin
+        @command.run
+        @mock_stdout.rewind
+        asset_equal @mock_stdout.read, <<-NEW_CRON
+# Something
+
+# Begin Whenever generated tasks for: My identifier
+#{@task}
+# End Whenever generated tasks for: My identifier
+NEW_CRON
+      rescue SystemExit => e
+        assert_equal 0, e.status
+      end
+    end
+  end
+
 end