diff --git a/ansi.py b/ansi.py
index b10ede3..738357c 100644
--- a/ansi.py
+++ b/ansi.py
@@ -3,7 +3,7 @@
 from collections import namedtuple
 from functools import partial
 import bisect
-import Default
+from .exec import ExecCommand
 import inspect
 import os
 import re
@@ -342,7 +342,7 @@ def _del_event_listeners(self, view):
         debug(view, "ANSIescape event listener removed from view.")
 
 
-class AnsiColorBuildCommand(Default.exec.ExecCommand):
+class AnsiColorBuildCommand(ExecCommand):
 
     process_trigger = "on_finish"
 
diff --git a/exec.py b/exec.py
new file mode 100644
index 0000000..95dde52
--- /dev/null
+++ b/exec.py
@@ -0,0 +1,320 @@
+import sublime, sublime_plugin
+import os, sys
+import threading
+import subprocess
+import functools
+import time
+import collections
+
+class ProcessListener(object):
+    def on_data(self, proc, data):
+        pass
+
+    def on_finished(self, proc):
+        pass
+
+# Encapsulates subprocess.Popen, forwarding stdout to a supplied
+# ProcessListener (on a separate thread)
+class AsyncProcess(object):
+    def __init__(self, cmd, shell_cmd, env, listener,
+            # "path" is an option in build systems
+            path="",
+            # "shell" is an options in build systems
+            shell=False):
+
+        if not shell_cmd and not cmd:
+            raise ValueError("shell_cmd or cmd is required")
+
+        if shell_cmd and not isinstance(shell_cmd, str):
+            raise ValueError("shell_cmd must be a string")
+
+        self.listener = listener
+        self.killed = False
+
+        self.start_time = time.time()
+
+        # Hide the console window on Windows
+        startupinfo = None
+        if os.name == "nt":
+            startupinfo = subprocess.STARTUPINFO()
+            startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
+
+        # Set temporary PATH to locate executable in cmd
+        if path:
+            old_path = os.environ["PATH"]
+            # The user decides in the build system whether he wants to append $PATH
+            # or tuck it at the front: "$PATH;C:\\new\\path", "C:\\new\\path;$PATH"
+            os.environ["PATH"] = os.path.expandvars(path)
+
+        proc_env = os.environ.copy()
+        proc_env.update(env)
+        for k, v in proc_env.items():
+            proc_env[k] = os.path.expandvars(v)
+
+        if shell_cmd and sys.platform == "win32":
+            # Use shell=True on Windows, so shell_cmd is passed through with the correct escaping
+            self.proc = subprocess.Popen(shell_cmd, stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE, startupinfo=startupinfo, env=proc_env, shell=True)
+        elif shell_cmd and sys.platform == "darwin":
+            # Use a login shell on OSX, otherwise the users expected env vars won't be setup
+            self.proc = subprocess.Popen(["/bin/bash", "-l", "-c", shell_cmd], stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE, startupinfo=startupinfo, env=proc_env, shell=False)
+        elif shell_cmd and sys.platform == "linux":
+            # Explicitly use /bin/bash on Linux, to keep Linux and OSX as
+            # similar as possible. A login shell is explicitly not used for
+            # linux, as it's not required
+            self.proc = subprocess.Popen(["/bin/bash", "-c", shell_cmd], stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE, startupinfo=startupinfo, env=proc_env, shell=False)
+        else:
+            # Old style build system, just do what it asks
+            self.proc = subprocess.Popen(cmd, stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE, startupinfo=startupinfo, env=proc_env, shell=shell)
+
+        if path:
+            os.environ["PATH"] = old_path
+
+        if self.proc.stdout:
+            threading.Thread(target=self.read_stdout).start()
+
+        if self.proc.stderr:
+            threading.Thread(target=self.read_stderr).start()
+
+    def kill(self):
+        if not self.killed:
+            self.killed = True
+            if sys.platform == "win32":
+                # terminate would not kill process opened by the shell cmd.exe, it will only kill
+                # cmd.exe leaving the child running
+                startupinfo = subprocess.STARTUPINFO()
+                startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
+                subprocess.Popen("taskkill /PID " + str(self.proc.pid), startupinfo=startupinfo)
+            else:
+                self.proc.terminate()
+            self.listener = None
+
+    def poll(self):
+        return self.proc.poll() == None
+
+    def exit_code(self):
+        return self.proc.poll()
+
+    def read_stdout(self):
+        while True:
+            data = os.read(self.proc.stdout.fileno(), 2**15)
+
+            if len(data) > 0:
+                if self.listener:
+                    self.listener.on_data(self, data)
+            else:
+                self.proc.stdout.close()
+                if self.listener:
+                    self.listener.on_finished(self)
+                break
+
+    def read_stderr(self):
+        while True:
+            data = os.read(self.proc.stderr.fileno(), 2**15)
+
+            if len(data) > 0:
+                if self.listener:
+                    self.listener.on_data(self, data)
+            else:
+                self.proc.stderr.close()
+                break
+
+class ExecCommand(sublime_plugin.WindowCommand, ProcessListener):
+    BLOCK_SIZE = 2**14
+    text_queue = collections.deque()
+    text_queue_proc = None
+    text_queue_lock = threading.Lock()
+
+    proc = None
+
+    def run(self, cmd = None, shell_cmd = None, file_regex = "", line_regex = "", working_dir = "",
+            encoding = "utf-8", env = {}, quiet = False, kill = False,
+            word_wrap = True, syntax = "Packages/Text/Plain text.tmLanguage",
+            # Catches "path" and "shell"
+            **kwargs):
+
+        # clear the text_queue
+        self.text_queue_lock.acquire()
+        try:
+            self.text_queue.clear()
+            self.text_queue_proc = None
+        finally:
+            self.text_queue_lock.release()
+
+        if kill:
+            if self.proc:
+                self.proc.kill()
+                self.proc = None
+                self.append_string(None, "[Cancelled]")
+            return
+
+        if not hasattr(self, 'output_view'):
+            # Try not to call get_output_panel until the regexes are assigned
+            self.output_view = self.window.create_output_panel("exec")
+
+        # Default the to the current files directory if no working directory was given
+        if (working_dir == "" and self.window.active_view()
+                        and self.window.active_view().file_name()):
+            working_dir = os.path.dirname(self.window.active_view().file_name())
+
+        self.output_view.settings().set("result_file_regex", file_regex)
+        self.output_view.settings().set("result_line_regex", line_regex)
+        self.output_view.settings().set("result_base_dir", working_dir)
+        self.output_view.settings().set("word_wrap", word_wrap)
+        self.output_view.settings().set("line_numbers", False)
+        self.output_view.settings().set("gutter", False)
+        self.output_view.settings().set("scroll_past_end", False)
+        self.output_view.assign_syntax(syntax)
+
+        # Call create_output_panel a second time after assigning the above
+        # settings, so that it'll be picked up as a result buffer
+        self.window.create_output_panel("exec")
+
+        self.encoding = encoding
+        self.quiet = quiet
+
+        self.proc = None
+        if not self.quiet:
+            if shell_cmd:
+                print("Running " + shell_cmd)
+            elif cmd:
+                print("Running " + " ".join(cmd))
+            sublime.status_message("Building")
+
+        show_panel_on_build = sublime.load_settings("Preferences.sublime-settings").get("show_panel_on_build", True)
+        if show_panel_on_build:
+            self.window.run_command("show_panel", {"panel": "output.exec"})
+
+        merged_env = env.copy()
+        if self.window.active_view():
+            user_env = self.window.active_view().settings().get('build_env')
+            if user_env:
+                merged_env.update(user_env)
+
+        # Change to the working dir, rather than spawning the process with it,
+        # so that emitted working dir relative path names make sense
+        if working_dir != "":
+            os.chdir(working_dir)
+
+        self.debug_text = ""
+        if shell_cmd:
+            self.debug_text += "[shell_cmd: " + shell_cmd + "]\n"
+        else:
+            self.debug_text += "[cmd: " + str(cmd) + "]\n"
+        self.debug_text += "[dir: " + str(os.getcwd()) + "]\n"
+        if "PATH" in merged_env:
+            self.debug_text += "[path: " + str(merged_env["PATH"]) + "]"
+        else:
+            self.debug_text += "[path: " + str(os.environ["PATH"]) + "]"
+
+        try:
+            # Forward kwargs to AsyncProcess
+            self.proc = AsyncProcess(cmd, shell_cmd, merged_env, self, **kwargs)
+
+            self.text_queue_lock.acquire()
+            try:
+                self.text_queue_proc = self.proc
+            finally:
+                self.text_queue_lock.release()
+
+        except Exception as e:
+            self.append_string(None, str(e) + "\n")
+            self.append_string(None, self.debug_text + "\n")
+            if not self.quiet:
+                self.append_string(None, "[Finished]")
+
+    def is_enabled(self, kill = False):
+        if kill:
+            return (self.proc != None) and self.proc.poll()
+        else:
+            return True
+
+    def append_string(self, proc, str):
+        self.text_queue_lock.acquire()
+
+        was_empty = False
+        try:
+            if proc != self.text_queue_proc:
+                # a second call to exec has been made before the first one
+                # finished, ignore it instead of intermingling the output.
+                if proc:
+                    proc.kill()
+                return
+
+            if len(self.text_queue) == 0:
+                was_empty = True
+                self.text_queue.append("")
+
+            available = self.BLOCK_SIZE - len(self.text_queue[-1])
+
+            if len(str) < available:
+                cur = self.text_queue.pop()
+                self.text_queue.append(cur + str)
+            else:
+                self.text_queue.append(str)
+
+        finally:
+            self.text_queue_lock.release()
+
+        if was_empty:
+            sublime.set_timeout(self.service_text_queue, 0)
+
+    def service_text_queue(self):
+        self.text_queue_lock.acquire()
+
+        is_empty = False
+        try:
+            if len(self.text_queue) == 0:
+                # this can happen if a new build was started, which will clear
+                # the text_queue
+                return
+
+            str = self.text_queue.popleft()
+            is_empty = (len(self.text_queue) == 0)
+        finally:
+            self.text_queue_lock.release()
+
+        self.output_view.run_command('append', {'characters': str, 'force': True, 'scroll_to_end': True})
+
+        if not is_empty:
+            sublime.set_timeout(self.service_text_queue, 1)
+
+    def finish(self, proc):
+        if not self.quiet:
+            elapsed = time.time() - proc.start_time
+            exit_code = proc.exit_code()
+            if exit_code == 0 or exit_code == None:
+                self.append_string(proc,
+                    ("[Finished in %.1fs]" % (elapsed)))
+            else:
+                self.append_string(proc, ("[Finished in %.1fs with exit code %d]\n"
+                    % (elapsed, exit_code)))
+                self.append_string(proc, self.debug_text)
+
+        if proc != self.proc:
+            return
+
+        errs = self.output_view.find_all_results()
+        if len(errs) == 0:
+            sublime.status_message("Build finished")
+        else:
+            sublime.status_message(("Build finished with %d errors") % len(errs))
+
+    def on_data(self, proc, data):
+        try:
+            str = data.decode(self.encoding)
+        except:
+            str = "[Decode error - output not " + self.encoding + "]\n"
+            proc = None
+
+        # Normalize newlines, Sublime Text always uses a single \n separator
+        # in memory.
+        str = str.replace('\r\n', '\n').replace('\r', '\n')
+
+        self.append_string(proc, str)
+
+    def on_finished(self, proc):
+        sublime.set_timeout(functools.partial(self.finish, proc), 0)