MOAR debugging: Print stdout,stderr line by line

scripts/run_cmd.py

 #!/usr/bin/env python
 # Copyright (c) 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 
 """Run a command and report its results in machine-readable format."""
 
 
 import collections
@@ skipping 167 matching lines @@
 
 
 def _get_result(popen):
   """Get the results from a running process. Blocks until the process completes.
 
   Args:
       popen: subprocess.Popen instance.
   Returns:
       A dictionary with stdout, stderr, and returncode as keys.
   """
-  print popen.stdout.read()
-  print popen.stderr.read()
+  for fd in (popen.stdout, popen.stderr):
+    for line in iter(fd.readline, ''):
+      print line
   stdout, stderr = popen.communicate()
   return CommandResults.make(stdout=stdout,
                              stderr=stderr,
                              returncode=popen.returncode)
 
 
 def run(cmd):
   """Run the command, block until it completes, and return a results dictionary.
 
   Args:
@@ skipping 152 matching lines @@
     setattr(options, cmd, args)
   except IndexError:
     parser.print_usage()
     sys.exit(1)
   return options
 
 
 if '__main__' == __name__:
   parsed_args = parse_args()
   run(parsed_args.cmd).print_results(pretty=parsed_args.pretty)