diff --git a/pydu/compat.py b/pydu/compat.py
index 33dccc3..90bfe6a 100644
--- a/pydu/compat.py
+++ b/pydu/compat.py
@@ -5,6 +5,13 @@ import types
 
 PY2 = sys.version_info[0] == 2
 
+
+# builtins
+if PY2:
+    import __builtin__ as builtins
+else:
+    import builtins
+
 # url*
 if PY2:
     import urllib as urlib
diff --git a/pydu/system.py b/pydu/system.py
index 765ee16..c9dd030 100644
--- a/pydu/system.py
+++ b/pydu/system.py
@@ -2,8 +2,64 @@ import os
 import sys
 import shutil
 
+from . import logger
 from .platform import WINDOWS
-from .compat import PY2
+from .compat import PY2, builtins
+
+
+_openfiles = set()
+_origin_open = builtins.open
+if PY2:
+    _origin_file = builtins.file
+
+    class _trackfile(builtins.file):
+        def __init__(self, *args):
+            self.path = args[0]
+            logger.debug('Opening "%s"', self.path)
+            super(_trackfile, self).__init__(*args)
+            _openfiles.add(self)
+
+        def close(self):
+            logger.debug('Closing "%s"', self.path)
+            super(_trackfile, self).close()
+            _openfiles.remove(self)
+
+
+    def _trackopen(*args):
+        return _trackfile(*args)
+else:
+    def _trackopen(*args, **kwargs):
+        f = _origin_open(*args, **kwargs)
+        path = args[0]
+        logger.debug('Opening "%s"', path)
+        _openfiles.add(f)
+
+        origin_close = f.close
+
+        def close():
+            logger.debug('Closing "%s"', path)
+            origin_close()
+            _openfiles.remove(f)
+        f.close = close
+        return f
+
+
+class FileTracker(object):
+    @classmethod
+    def track(cls):
+        builtins.open = _trackopen
+        if PY2:
+            builtins.file = _trackfile
+
+    @classmethod
+    def untrack(cls):
+        builtins.open = _origin_open
+        if PY2:
+            builtins.file = _origin_file
+
+    @classmethod
+    def get_openfiles(cls):
+        return _openfiles
 
 
 def makedirs(path, mode=0o755, ignore_errors=False, exist_ok=False):
diff --git a/tests/test_system.py b/tests/test_system.py
index 983bc81..af57f5c 100644
--- a/tests/test_system.py
+++ b/tests/test_system.py
@@ -4,13 +4,38 @@ import time
 import pytest
 
 from pydu.platform import WINDOWS
-from pydu.system import (makedirs, remove, removes, open_file, copy, touch,
+from pydu.system import (FileTracker,
+                         makedirs, remove, removes, open_file, copy, touch,
                          chmod, which)
 
 if not WINDOWS:
     from pydu.system import link, symlink
 
 
+class TestFileTracker:
+    def test_track_open(self, tmpdir):
+        FileTracker.track()
+        path = tmpdir.join('test').strpath
+        f = open(path, 'w')
+        assert f in FileTracker.get_openfiles()
+        f.close()
+        assert f not in FileTracker.get_openfiles()
+
+    def test_track_context_open(self, tmpdir):
+        FileTracker.track()
+        path = tmpdir.join('test').strpath
+        with open(path, 'w') as f:
+            assert f in FileTracker.get_openfiles()
+        assert f not in FileTracker.get_openfiles()
+
+    def test_untrack(self, tmpdir):
+        FileTracker.track()
+        FileTracker.untrack()
+        path = tmpdir.join('test').strpath
+        f = open(path, 'w')
+        assert f not in FileTracker.get_openfiles()
+
+
 class TestMakeDirs:
     def test_makedirs(self, tmpdir):
         path = str(tmpdir.join('test'))