#
# Copyright (C) 2010-2017 Samuel Abels
# The MIT License (MIT)
#
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# a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
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# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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"""
A class for catching SIGINT, such that CTRL+c works.
"""
from __future__ import print_function
from builtins import object
import os
import sys
import signal
[docs]class SigIntWatcher(object):
"""
This class solves two problems with multithreaded programs in Python:
- A signal might be delivered to any thread and
- if the thread that gets the signal is waiting, the signal
is ignored (which is a bug).
This class forks and catches sigint for Exscript.
The watcher is a concurrent process (not thread) that waits for a
signal and the process that contains the threads.
Works on Linux, Solaris, MacOS, and AIX. Known not to work
on Windows.
"""
[docs] def __init__(self):
"""
Creates a child process, which returns. The parent
process waits for a KeyboardInterrupt and then kills
the child process.
"""
try:
self.child = os.fork()
except AttributeError: # platforms that don't have os.fork
pass
except RuntimeError:
pass # prevent "not holding the import lock" on some systems.
if self.child == 0:
return
else:
self.watch()
[docs] def watch(self):
try:
pid, status = os.wait()
except KeyboardInterrupt:
print('********** SIGINT RECEIVED - SHUTTING DOWN! **********')
self.kill()
sys.exit(1)
sys.exit(status >> 8)
[docs] def kill(self):
try:
os.kill(self.child, signal.SIGKILL)
except OSError:
pass