Set up default SIGPIPE handler

This lets you do something like "nilmtool extract | head" without
triggering backtraces.

nilmdb/cmdline/cmdline.py

@@ -10,6 +10,7 @@ import sys
 import os
 import argparse
 from argparse import ArgumentDefaultsHelpFormatter as def_form
+import signal
 
 try: # pragma: no cover
     import argcomplete
@@ -126,6 +127,13 @@ class Cmdline(object):
         sys.exit(-1)
 
     def run(self):
+        # Set SIGPIPE to its default handler -- we don't need Python
+        # to catch it for us.
+        try:
+            signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+        except ValueError: # pragma: no cover
+            pass
+
         # Clear cached timezone, so that we can pick up timezone changes
         # while running this from the test suite.
         datetime_tz._localtz = None

nilmdb/utils/time.py

@@ -6,7 +6,7 @@ import time
 
 # Range
 min_timestamp = (-2**63)
-max_timestamp = (2**62 - 1)
+max_timestamp = (2**63 - 1)
 
 # Smallest representable step
 epsilon = 1
@@ -32,6 +32,10 @@ def timestamp_to_human(timestamp):
     """Convert a timestamp (integer microseconds since epoch) to a
     human-readable string, using the local timezone for display
     (e.g. from the TZ env var)."""
+    if timestamp == min_timestamp:
+        return "(minimum)"
+    if timestamp == max_timestamp:
+        return "(maximum)"
     dt = datetime_tz.datetime_tz.fromtimestamp(timestamp_to_unix(timestamp))
     return dt.strftime("%a, %d %b %Y %H:%M:%S.%f %z")
 

tests/test_cmdline.py

@@ -615,7 +615,7 @@ class TestCmdline(object):
         test(8, "10:01:59.9", "10:02:00.1", extra="-m")
 
         # all data put in by tests
-        self.ok("extract -a /newton/prep --start 2000-01-01 --end 2020-01-01")
+        self.ok("extract -a /newton/prep --start min --end max")
         lines_(self.captured, 43204)
         self.ok("extract -c /newton/prep --start 2000-01-01 --end 2020-01-01")
         self.match("43200\n")