[Android] Add IterShell command to iterate over output lines

build/android/pylib/device/adb_wrapper.py

 # Copyright 2013 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.
 
 """This module wraps Android's adb tool.
 
 This is a thin wrapper around the adb interface. Any additional complexity
 should be delegated to a higher level (ex. DeviceUtils).
 """
 
@@ skipping 235 matching lines @@
       except ValueError:
         logging.warning('exit status of shell command %r missing.', command)
         raise device_errors.AdbShellCommandFailedError(
             command, output, status=None, device_serial=self._device_serial)
       output = output[:output_end]
       if status != expect_status:
         raise device_errors.AdbShellCommandFailedError(
             command, output, status=status, device_serial=self._device_serial)
     return output
 
+  def IterShell(self, command, timeout):

[jbudorick, 2015/02/09 14:21:38]

My concern here is that we don't do the same exit status checking as Shell. What
would it take to do that, and what would the experience be like from the client
side (i.e. would it make sense)?

[perezju, 2015/02/09 16:39:12]

We had the same discussion regarding Logcat :)

1. We _do_ already check the exit status on the host, the corresponding
cmd_helper command will raise a CalledProcessError if the exit status is
non-zero.

2. There is no reliable way to get the exit status from the device, as we never
know whether we've just read "the last line of output" from the command, or more
lines are to follow.

[jbudorick, 2015/02/09 16:39:59]

Well, at least I'm consistent :)
sgtm

+    """Runs a shell command and returns an iterator over its output lines.
+
+    Args:
+      command: A string with the shell command to run.
+      timeout: Timeout in seconds.
+
+    Yields:
+      The output of the command line by line.
+    """
+    args = ['shell', command]
+    return cmd_helper.IterCmdOutputLines(
+      self._BuildAdbCmd(args, self._device_serial), timeout=timeout)
+
   def Ls(self, path, timeout=_DEFAULT_TIMEOUT, retries=_DEFAULT_RETRIES):
     """List the contents of a directory on the device.
 
     Args:
       path: Path on the device filesystem.
       timeout: (optional) Timeout per try in seconds.
       retries: (optional) Number of retries to attempt.
 
     Returns:
       A list of pairs (filename, stat) for each file found in the directory,
@@ skipping 220 matching lines @@
     """Restarts the adbd daemon with root permissions, if possible.
 
     Args:
       timeout: (optional) Timeout per try in seconds.
       retries: (optional) Number of retries to attempt.
     """
     output = self._RunDeviceAdbCmd(['root'], timeout, retries)
     if 'cannot' in output:
       raise device_errors.AdbCommandFailedError(
           ['root'], output, device_serial=self._device_serial)