Add value format for list command

The value format for the show command is very handy for shell
scripting and a value format for the list command would be just
as handy.  It will allow command substitution and piping like:

    os container list --format value | grep tmp | while read NAME
    do
      os container delete $NAME
    done

Change-Id: If9784c27d689073e9145b2cb8077ac604025a4c3

1 files changed, 9 insertions, 1 deletions

diff --git a/cliff/formatters/value.py b/cliff/formatters/value.py
index 9910319..6cc6744 100644
--- a/cliff/formatters/value.py
+++ b/cliff/formatters/value.py
@@ -1,14 +1,22 @@
 """Output formatters values only
 """
 
+import six
+
+from .base import ListFormatter
 from .base import SingleFormatter
 
 
-class ValueFormatter(SingleFormatter):
+class ValueFormatter(ListFormatter, SingleFormatter):
 
     def add_argument_group(self, parser):
         pass
 
+    def emit_list(self, column_names, data, stdout, parsed_args):
+        for row in data:
+            stdout.write(' '.join(map(six.text_type, row)) + u'\n')
+        return
+
     def emit_one(self, column_names, data, stdout, parsed_args):
         for value in data:
             stdout.write('%s\n' % str(value))