Index: test/lit.cfg
===================================================================
--- test/lit.cfg
+++ test/lit.cfg
@@ -13,6 +13,7 @@
 import sys
 import tempfile
 import time
+import pty
 
 import lit.Test
 import lit.formats
@@ -35,8 +36,54 @@
         self.cpp_flags = list(cpp_flags)
         self.ld_flags = list(ld_flags)
         self.exec_env = dict(exec_env)
-
-    def execute_command(self, command, in_dir=None):
+        if sys.stdout.isatty():
+            self._execute_command_helper = LibcxxTestFormat._execute_command_pty
+        else:
+            self._execute_command_helper = LibcxxTestFormat._execute_command_normal
+
+    @staticmethod
+    def _close_raw_fd(fd):
+        try:
+            os.close(fd)
+        except:
+            pass
+
+    @staticmethod
+    def _read_and_close_pty(p):
+        os.close(p[1])
+        with os.fdopen(p[0], 'r') as f:
+            out = ''
+            try:
+                out = f.read()
+            except IOError:
+                pass
+            return out
+
+    @staticmethod
+    def _execute_command_pty(command, in_dir=None):
+        try:
+            out_pty = tuple(pty.openpty())
+            err_pty = tuple(pty.openpty())
+            kwargs = {
+                'stdin' :subprocess.PIPE,
+                'stdout':out_pty[1],
+                'stderr':err_pty[1],
+                'close_fds':True,
+            }
+            if in_dir:
+                kwargs['cwd'] = in_dir
+            p = subprocess.Popen(command, **kwargs)
+            exitCode = p.wait()
+            out = LibcxxTestFormat._read_and_close_pty(out_pty)
+            err = LibcxxTestFormat._read_and_close_pty(err_pty)
+        except:
+            for fd in out_pty + err_pty:
+                LibcxxTestFormat._close_raw_fd(fd)
+            raise
+        return out,err,exitCode
+
+    @staticmethod
+    def _execute_command_normal(command, in_dir=None):
         kwargs = {
             'stdin' :subprocess.PIPE,
             'stdout':subprocess.PIPE,
@@ -47,11 +94,13 @@
         p = subprocess.Popen(command, **kwargs)
         out,err = p.communicate()
         exitCode = p.wait()
+        return out,err,exitCode
 
+    def execute_command(self, command, in_dir=None):
+        out,err,exitCode = self._execute_command_helper(command, in_dir)
         # Detect Ctrl-C in subprocess.
         if exitCode == -signal.SIGINT:
             raise KeyboardInterrupt
-
         return out, err, exitCode
 
     def execute(self, test, lit_config):