diff --git a/.gitignore b/.gitignore
index d0056c2..350eada 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,7 +2,7 @@
 /libs/
 /.crystal/
 /.shards/
-guardian
+/bin/guardian
 
 
 # Libraries don't need dependency lock
diff --git a/README.md b/README.md
index 25ec118..bbd6833 100644
--- a/README.md
+++ b/README.md
@@ -75,14 +75,14 @@ run: shards install
 
 ### `%file%` Variable
 
-Guardian replaces `%file%` variable in commands with the changed file.
+Guardian replaces `%file%` variable in commands with the changed file(s).
 
 ```yaml
 files: ./**/*.txt
 run: echo "%file% is changed"
 ```
 
-Think you have a `hello.txt` in your directory, and Guardian will run `echo "hello.txt is changed"` command when it's changed.
+Think you have a `hello.txt` & `goodbye.txt` in your directory, and Guardian will run `echo "hello.txt goodbye.txt is changed"` command when it's changed.
 
 ## Running Guardian
 
diff --git a/shard.yml b/shard.yml
index 5549d8e..61447c7 100644
--- a/shard.yml
+++ b/shard.yml
@@ -9,6 +9,11 @@ targets:
   guardian:
     main: src/guardian.cr
 
+dependencies:
+  pty:
+    github: crystal-posix/pty.cr
+    branch: main
+
 crystal: 0.35.1
 
 license: MIT
diff --git a/src/guardian.cr b/src/guardian.cr
index b110805..9b3b47d 100644
--- a/src/guardian.cr
+++ b/src/guardian.cr
@@ -4,6 +4,7 @@ require "colorize"
 
 ignore_executables = true
 clear_on_action = false
+verbose = 0
 case ARGV[0]?
 when "init"
   puts "\"init\" has been deprecated please use: -i or --init"
@@ -38,6 +39,10 @@ else
       clear_on_action = true
     end
 
+    options.on "--verbose", "More logging" do
+      verbose += 1
+    end
+
     options.invalid_option do
       puts options
       exit
@@ -45,4 +50,13 @@ else
   end
 end
 
-Guardian::Watcher.new ignore_executables, clear_on_action
+watcher = Guardian::Watcher.new ignore_executables, verbose, clear_on_action
+Signal::HUP.trap { watcher.shutdown }
+Signal::QUIT.trap { watcher.shutdown }
+Signal::TERM.trap { watcher.shutdown }
+begin
+  watcher.run
+ensure
+  watcher.close
+  # puts Dir.glob("/tmp/guardian*")
+end
diff --git a/src/guardian/command_run.cr b/src/guardian/command_run.cr
new file mode 100644
index 0000000..4c0de4c
--- /dev/null
+++ b/src/guardian/command_run.cr
@@ -0,0 +1,90 @@
+require "pty/process"
+
+module Guardian
+  class CommandRun
+    # Only used with %file% substitution
+    enum MissingFiles
+      # (default) Removes missing files from the command args
+      # Suitable for use with `crystal spec`
+      Remove
+      # Keep missing files as command arguments
+      Preserve
+      # Skip running the command when any files are missing
+      SkipCommand
+      # Remove all %file% args from command
+      # Suitable for use with `crystal spec`
+      StripArgs
+    end
+
+    private FILE_NULL = File.new(File::NULL, "r")
+
+    private getter? has_command_substitution : Bool
+    @process_output = Pty::Process.new
+    @temp_file : File = File.tempfile("guardian", ".out")
+
+    @modified_files = Set(String).new
+
+    def initialize(@raw_command : String, missing_files : String)
+      @missing_files = MissingFiles.parse(missing_files)
+      @has_command_substitution = /%file%/ === @raw_command
+    end
+
+    def enqueue(file) : Nil
+      @modified_files << file
+    end
+
+    # returns true(success), false(failure)
+    def run : Bool
+      cmd = command
+      return true unless command
+
+      win_size = Pty.tty_win_size
+      win_size = {win_size[0 - 2], win_size[1]} if win_size
+
+      @temp_file.truncate 0
+      _, status = @process_output.run(command.not_nil!, input: FILE_NULL, shell: true, win_size: win_size) do |_, _, outputerr|
+        IO.copy outputerr, @temp_file
+        nil
+      end
+
+      if status.success?
+        STDOUT.puts "#{"✔".colorize(:green)} #{"$".colorize(:dark_gray)} #{cmd.colorize(:cyan)}"
+      else
+        STDOUT.puts "#{"✖".colorize(:red)} #{"$".colorize(:dark_gray)} #{cmd.colorize(:cyan)}"
+        @temp_file.rewind
+        @temp_file.each_line do |line|
+          puts "  #{line.gsub(/\n$/, "").colorize(:dark_gray)}"
+        end
+      end
+
+      status.success?
+    ensure
+      @modified_files.clear
+    end
+
+    def close
+      @process_output.signal? Signal::TERM
+      @temp_file.close
+      @temp_file.delete rescue nil
+    end
+
+    private def command : String?
+      if has_command_substitution?
+        existing_files = @modified_files.select { |file|
+          File.exists?(file)
+        }.to_a
+        if existing_files.size == @modified_files.size || @missing_files.remove?
+          @raw_command.gsub(/%file%/, existing_files.join(" "))
+        elsif @missing_files.strip_args?
+          @raw_command
+        elsif @missing_files.skip_command?
+          nil
+        else
+          raise "unsupported missing_files value #{@missing_files.inspect}"
+        end
+      else
+        @raw_command
+      end
+    end
+  end
+end
diff --git a/src/guardian/watcher.cr b/src/guardian/watcher.cr
index 99df2e7..b9cf584 100644
--- a/src/guardian/watcher.cr
+++ b/src/guardian/watcher.cr
@@ -1,6 +1,7 @@
 require "yaml"
 require "colorize"
 require "file"
+require "./command_run"
 
 module Guardian
   class WatcherYML
@@ -8,21 +9,28 @@ module Guardian
 
     property files : String
     property run : String
-  end
+    property missing_files = "remove"
 
+    @[YAML::Field(ignore: true)]
+    @command : CommandRun?
 
+    def command
+      @command ||= CommandRun.new(run, missing_files)
+    end
+  end
 
   class Watcher
-    setter files
+    @files = Set(String).new
+    @runners = Hash(String, Set(CommandRun)).new { |h, k| h[k] = Set(CommandRun).new }
+    @timestamps = {} of String => Time
+    @watchers = [] of WatcherYML
 
-    def initialize(@ignore_executables = true, @clear_on_action = false)
-      file = "./guardian.yml"
+    @task_queue = Set(CommandRun).new
 
-      @files = [] of String
-      @runners = {} of String => Array(String)
-      @timestamps = {} of String => Time
-      @watchers = [] of WatcherYML
+    @shutdown = false
 
+    def initialize(@ignore_executables = true, @verbose = 0, @clear_on_action = false)
+      file = "guardian.yml"
       if File.exists?(file) || File.exists?(file = file.insert(2, '.'))
         YAML.parse_all(File.read(file)).each do |yaml|
           @watchers << WatcherYML.from_yaml(yaml.to_yaml)
@@ -31,7 +39,9 @@ module Guardian
         puts "#{"guardian.yml".colorize(:red)} does not exist!"
         exit 1
       end
+    end
 
+    def run
       collect_files
       start_watching
     end
@@ -49,7 +59,11 @@ module Guardian
       loop do
         watch_changes
         watch_newfiles
+        break if @shutdown
+        run_tasks
+        break if @shutdown
         sleep 1
+        break if @shutdown
       end
     end
 
@@ -58,9 +72,9 @@ module Guardian
     end
 
     def collect_files
-      @files = [] of String
-      @runners = {} of String => Array(String)
-      @timestamps = {} of String => Time
+      @files.clear
+      @runners.clear
+      @timestamps.clear
 
       @watchers.each do |watcher|
         Dir.glob(watcher.files) do |file|
@@ -68,25 +82,40 @@ module Guardian
             @files << file
             @timestamps[file] = file_creation_date(file)
 
-            unless @runners.has_key? file
-              @runners[file] = [watcher.run]
-            else
-              @runners[file] << watcher.run
-            end
+            puts "runner #{file.inspect} -> #{watcher.run.inspect} #{@runners[file].size}" if @verbose > 0
+            @runners[file] << watcher.command
           end
         end
       end
     end
 
-    def run_tasks(file)
-      @runners[file].each do |command|
-        command = command.gsub(/%file%/, file)
-        puts "#{"$".colorize(:dark_gray)} #{command.colorize(:cyan)}"
-        output = `#{command}`
-        output.lines.each do |line|
-          puts "  #{line.gsub(/\n$/, "").colorize(:dark_gray)}"
-        end
+    # Multiple files may trigger the same command
+    # Queue and dedup them
+    private def queue_tasks(file)
+      commands = @runners[file]
+      commands.each do |command|
+        command.enqueue file
+        @task_queue << command
+      end
+    end
+
+    private def run_tasks : Nil
+      return if @task_queue.empty?
+
+      errors = 0
+      @task_queue.each do |command|
+        success = command.run
+        errors += 1 unless success
+        break if @shutdown
+      end
+
+      if errors == 0
+        puts "◼".colorize(:dark_gray)
+      else
+        puts "#{"◼".colorize(:red)} errors=#{errors}"
       end
+    ensure
+      @task_queue.clear
     end
 
     def watch_changes
@@ -112,18 +141,18 @@ module Guardian
               end
             end
             @timestamps[file] = check_time
-            run_tasks file
+            queue_tasks file
           end
         rescue
           puts "#{"-".colorize(:red)} #{file}"
-          run_tasks file
+          queue_tasks file
           collect_files
         end
       end
     end
 
     def watch_newfiles
-      files = [] of String
+      files = Set(String).new
       @watchers.each do |watcher|
         Dir.glob(watcher.files) do |file|
           if watch_file? file
@@ -138,7 +167,7 @@ module Guardian
         new_files.each do |file|
           puts "#{"+".colorize(:green)} #{file}"
           collect_files
-          run_tasks file
+          queue_tasks file
         end
       end
     end
@@ -147,5 +176,15 @@ module Guardian
       return unless @clear_on_action
       system "clear"
     end
+
+    def shutdown
+      puts "shutting down" if @verbose > 0
+      @shutdown = true
+    end
+
+    def close
+      # Cleanup temp files
+      @watchers.each &.command.close
+    end
   end
 end