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100 lines
2.8 KiB
Python
100 lines
2.8 KiB
Python
import os
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import signal
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import errno
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def get_command(pid):
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"""Figures out the associated command name
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of a process with the given pid.
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Args:
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pid (int): the pid of the process of interest
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Returns:
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str: the associated command name
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"""
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with open('/proc/{}/comm'.format(pid), 'r') as commfile:
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return '\n'.join(commfile.readlines())
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def is_same_command(pid0, pid1):
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"""Checks whether the associated command name
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of the processes of the given pids equals to each other.
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Args:
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pid0 (int): the pid of the process of interest
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pid1 (int): the pid of another process of interest
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Returns:
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bool: True if both processes have
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the same associated command name
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"""
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return get_command(pid0) == get_command(pid1)
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def send_signal_safe(own_pid, target_pid):
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"""Sends SIGUSR1 to a process if both
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processes have the same associated command name.
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(Race condition free)
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Requires:
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- Python 3.9+
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- Linux 5.1+
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Args:
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own_pid (int): the pid of this process
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target_pid (int):
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the pid of the process to send the signal to
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"""
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pidfile = None
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try:
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pidfile = os.open(f'/proc/{target_pid}', os.O_DIRECTORY)
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if is_same_command(own_pid, target_pid):
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signal.pidfd_send_signal(pidfile, signal.SIGUSR1)
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except FileNotFoundError:
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pass
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except OSError as error:
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# not sure if errno is really set..
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# at least the documentation of the used functions says so..
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# see e.g.: https://github.com/python/cpython/commit/7483451577916e693af6d20cf520b2cc7e2174d2#diff-99fb04b208835118fdca0d54b76a00c450da3eaff09d2b53e8a03d63bbe88e30R1279-R1281
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# and https://docs.python.org/3/c-api/exceptions.html#c.PyErr_SetFromErrno
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# caused by either pidfile_open or pidfd_send_signal
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if error.errno != errno.ESRCH:
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raise
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# else: the process is death
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finally:
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if pidfile is not None:
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os.close(pidfile)
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def send_signal_unsafe(own_pid, target_pid):
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"""Sends SIGUSR1 to a process if both
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processes have the same associated command name.
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(Race condition if process dies)
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Args:
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own_pid (int): the pid of this process
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target_pid (int):
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the pid of the process to send the signal to
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"""
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try:
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if is_same_command(own_pid, target_pid):
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os.kill(target_pid, signal.SIGUSR1)
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except (FileNotFoundError, ProcessLookupError):
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pass
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def main(options):
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# assumption:
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# started by calling the programs name
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# ueberzug layer and
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# ueberzug query_windows
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own_pid = os.getpid()
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for pid in options['PIDS']:
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try:
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send_signal_safe(own_pid, int(pid))
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except AttributeError:
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send_signal_unsafe(own_pid, int(pid))
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