#!/usr/bin/env python
# cardinal_pythonlib/signalfunc.py
"""
===============================================================================
Original code copyright (C) 2009-2022 Rudolf Cardinal (rudolf@pobox.com).
This file is part of cardinal_pythonlib.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
https://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
===============================================================================
**Support functions to handle OS signals that may cause trouble.**
"""
import platform
import signal
from cardinal_pythonlib.logs import get_brace_style_log_with_null_handler
log = get_brace_style_log_with_null_handler(__name__)
# =============================================================================
# Signal handlers
# =============================================================================
# noinspection PyUnusedLocal
[docs]def ctrl_c_trapper(signum: int, stackframe) -> None:
"""
Logs that ``CTRL-C`` has been pressed but does nothing else.
"""
log.critical("Ignoring CTRL+C (signal {}); use the GUI to quit", signum)
# noinspection PyUnusedLocal
[docs]def ctrl_break_trapper(signum: int, stackframe) -> None:
"""
Logs that ``CTRL-BREAK`` has been pressed but does nothing else.
"""
log.critical(
"Ignoring CTRL+BREAK (signal {}); use the GUI to quit", signum
)
# noinspection PyUnusedLocal
[docs]def sigterm_trapper(signum: int, stackframe) -> None:
"""
Logs that ``SIGTERM`` has been received but does nothing else.
"""
log.critical("Ignoring SIGTERM (signal {}); use the GUI to quit", signum)
[docs]def trap_ctrl_c_ctrl_break() -> None:
"""
Prevent ``CTRL-C``, ``CTRL-BREAK``, and similar signals from doing
anything.
See
- https://docs.python.org/3/library/signal.html#signal.SIG_IGN
- https://msdn.microsoft.com/en-us/library/xdkz3x12.aspx
- https://msdn.microsoft.com/en-us/library/windows/desktop/ms682541(v=vs.85).aspx
Under Windows, the only options are:
=========== ======================= =====================================
Signal Meaning Comment
=========== ======================= =====================================
SIGABRT abnormal termination
SIGFPE floating-point error
SIGILL illegal instruction
SIGINT CTRL+C signal -- trapped here
SIGSEGV illegal storage access
SIGTERM termination request -- trapped here
SIGBREAK CTRL+BREAK -- trapped here under Windows
=========== ======================= =====================================
In Linux, you also find:
=========== =============================
Signal Meaning
=========== =============================
SIGBUS bus error / unaligned access
=========== =============================
To ignore, can do:
.. code-block:: python
signal.signal(signal.SIGINT, signal.SIG_IGN) # SIG_IGN = "ignore me"
or pass a specified handler, as in the code here.
""" # noqa
signal.signal(signal.SIGINT, ctrl_c_trapper)
signal.signal(signal.SIGTERM, sigterm_trapper)
if platform.system() == "Windows":
# SIGBREAK isn't in the Linux signal module
# noinspection PyUnresolvedReferences
signal.signal(signal.SIGBREAK, ctrl_break_trapper)