[Android] Add IterShell command to iterate over output lines

build/android/pylib/device/adb_wrapper.py

Index: build/android/pylib/device/adb_wrapper.py
diff --git a/build/android/pylib/device/adb_wrapper.py b/build/android/pylib/device/adb_wrapper.py
index 7d11671212d236fcb9a4d6a7dc738775ef93d29f..de611ee0756d0f274c0b5ced827edc4a36d8e1a0 100644
--- a/build/android/pylib/device/adb_wrapper.py
+++ b/build/android/pylib/device/adb_wrapper.py
@@ -253,6 +253,20 @@ class AdbWrapper(object):
             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.