diff --git a/tools/patman/command.py b/tools/patman/command.py
index bf8ea6c..d54b1e0 100644
--- a/tools/patman/command.py
+++ b/tools/patman/command.py
@@ -49,7 +49,8 @@
 
 def RunPipe(pipe_list, infile=None, outfile=None,
             capture=False, capture_stderr=False, oneline=False,
-            raise_on_error=True, cwd=None, binary=False, **kwargs):
+            raise_on_error=True, cwd=None, binary=False,
+            output_func=None, **kwargs):
     """
     Perform a command pipeline, with optional input/output filenames.
 
@@ -63,6 +64,8 @@
         capture: True to capture output
         capture_stderr: True to capture stderr
         oneline: True to strip newline chars from output
+        output_func: Output function to call with each output fragment
+            (if it returns True the function terminates)
         kwargs: Additional keyword arguments to cros_subprocess.Popen()
     Returns:
         CommandResult object
@@ -105,7 +108,7 @@
 
     if capture:
         result.stdout, result.stderr, result.combined = (
-                last_pipe.CommunicateFilter(None))
+                last_pipe.CommunicateFilter(output_func))
         if result.stdout and oneline:
             result.output = result.stdout.rstrip(b'\r\n')
         result.return_code = last_pipe.wait()