proxy show: uses $PAGER to paginate output

slapos/cli/proxy_show.py

@@ -32,6 +32,9 @@ import hashlib
 import json
 import logging
 import sys
+import os
+import subprocess
+import StringIO
 
 import lxml.etree
 import prettytable
@@ -201,9 +204,13 @@ def log_network(logger, conn):
 
 def do_show(conf):
     # Because this command uses logging facility to output,
-    # setup a logger which displays on stdout.
+    # setup a logger which displays on stdout and uses a pager
+    # to paginate input, honoring $PAGER.
+    output = sys.stdout
+    if output.isatty():
+       output = StringIO.StringIO()
     proxy_show_logger = logging.getLogger(__name__)
-    handler = logging.StreamHandler(sys.stdout)
+    handler = logging.StreamHandler(output)
     handler.setLevel(logging.DEBUG)
     formatter = logging.Formatter('%(message)s')
     handler.setFormatter(formatter)
@@ -234,3 +241,11 @@ def do_show(conf):
         func(proxy_show_logger, conn)
         if idx < len(to_call) - 1:
             proxy_show_logger.info(' ')
+
+    if sys.stdout.isatty():
+        pager = subprocess.Popen(
+            os.getenv('PAGER', 'less --quit-if-one-screen --no-init'),
+            close_fds=True,
+            shell=True,
+            stdin=subprocess.PIPE,)
+        pager.communicate(output.getvalue().encode('utf-8'))

slapos/tests/cli.py

@@ -166,6 +166,29 @@ class TestCliProxyShow(CliMixin):
     self.assertIn('287375f0cba269902ba1bc50242839d7', stdout.getvalue())
     self.assertEqual('', stderr.getvalue())
 
+  def test_proxy_show_use_pager(self):
+    saved_stderr = sys.stderr
+    saved_stdout = sys.stdout
+    sys.stderr = stderr = StringIO.StringIO()
+    sys.stdout = stdout = StringIO.StringIO()
+    stdout.isatty = lambda *args: True
+
+    # use a pager that just output to a file.
+    tmp = tempfile.NamedTemporaryFile(delete=False)
+    self.addCleanup(os.unlink, tmp.name)
+    os.environ['PAGER'] = 'cat > {}'.format(tmp.name)
+
+    try:
+      slapos.cli.proxy_show.do_show(self.conf)
+    finally:
+      sys.stderr = saved_stderr
+      sys.stdout = saved_stdout
+
+    self.assertEqual('', stdout.getvalue())
+    self.assertEqual('', stderr.getvalue())
+    # our pager was set to output to this temporary file
+    self.assertIn('287375f0cba269902ba1bc50242839d7', open(tmp.name, 'r').read())
+
 
 class TestCliNode(CliMixin):