output: Add new output mode: cmd.

This new output is thought to be used when executing a command in a VM/VMSS.
It permits to print the output of the command like if this was executed locally.

Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>

knack/output.py

@@ -8,6 +8,7 @@
 import traceback
 from collections import OrderedDict
 from io import StringIO
+import sys
 
 from .events import EVENT_INVOKER_POST_PARSE_ARGS, EVENT_PARSER_GLOBAL_CREATE
 from .log import get_logger
@@ -29,6 +30,39 @@ def default(self, o):  # pylint: disable=method-hidden
             return o.decode()
         return json.JSONEncoder.default(self, o)
 
+def format_cmd(obj):
+    result = obj.result
+    if not 'value' in result:
+        raise CLIError("Table output unavailable. "
+                       "Use the --query option to specify an appropriate query. "
+                       "Use --debug for more info.")
+
+    value = result['value'][0]
+    if not 'message' in value:
+        raise CLIError("Table output unavailable. "
+                       "Use the --query option to specify an appropriate query. "
+                       "Use --debug for more info.")
+
+    message = value['message']
+
+    stdout_begin = message.find("[stdout]\n")
+    stderr_begin = message.find("[stderr]\n")
+    if stdout_begin == -1 or stderr_begin == -1:
+        raise CLIError("Table output unavailable. "
+                       "Use the --query option to specify an appropriate query. "
+                       "Use --debug for more info.")
+
+    stdout_begin += len("[stdout]\n")
+    # We remove two to avoid the last \n.
+    stderr_output = message[stdout_begin:stderr_begin - 2]
+
+    stderr_begin += len("[stderr]\n")
+    stdout_output = message[stderr_begin:-2]
+
+    print(stderr_output, file = sys.stderr)
+
+    return stdout_output
+
 
 def format_json(obj):
     result = obj.result
@@ -99,6 +133,7 @@ class OutputProducer(object):
         'table': format_table,
         'tsv': format_tsv,
         'none': format_none,
+        'cmd': format_cmd,
     }
 
     @staticmethod