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#!/usr/bin/env python3
"""Exec a command with PR_SET_PDEATHSIG — receive a signal when parent dies.
Usage: pdeathsig.py SIGNAL COMMAND [ARGS...]
Fallback for systems without `setpriv --pdeathsig`.
"""
import ctypes
import ctypes.util
import os
import signal
import sys
PR_SET_PDEATHSIG = 1
SIGNALS = {
"TERM": signal.SIGTERM, "SIGTERM": signal.SIGTERM,
"INT": signal.SIGINT, "SIGINT": signal.SIGINT,
"HUP": signal.SIGHUP, "SIGHUP": signal.SIGHUP,
"KILL": signal.SIGKILL, "SIGKILL": signal.SIGKILL,
}
def main() -> int:
if len(sys.argv) < 3:
print(f"usage: {sys.argv[0]} SIGNAL COMMAND [ARGS...]", file=sys.stderr)
return 2
sig_name = sys.argv[1]
argv = sys.argv[2:]
if sig_name not in SIGNALS:
print(f"unknown signal: {sig_name}", file=sys.stderr)
return 2
sig = SIGNALS[sig_name]
libc = ctypes.CDLL(ctypes.util.find_library("c") or "libc.so.6", use_errno=True)
if libc.prctl(PR_SET_PDEATHSIG, sig, 0, 0, 0) != 0:
err = ctypes.get_errno()
raise OSError(err, os.strerror(err))
# Race fix: parent may have died before prctl took effect
if os.getppid() == 1:
os.kill(os.getpid(), sig)
os.execvp(argv[0], argv)
return 127
if __name__ == "__main__":
raise SystemExit(main())
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