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#!/usr/bin/env python3
# SPDX-License-Identifier: MPL-2.0
#
# libpathrs: safe path resolution on Linux
# Copyright (C) 2019-2025 Aleksa Sarai <cyphar@cyphar.com>
# Copyright (C) 2019-2025 SUSE LLC
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at https://mozilla.org/MPL/2.0/.
# File: examples/python/sysctl.py
#
# An example program which does sysctl operations using the libpathrs safe
# procfs API.
import os
import sys
sys.path.append(os.path.dirname(__file__) + "/../contrib/bindings/python")
from pathrs import procfs
from pathrs.procfs import ProcfsHandle
def bail(*args):
print("[!]", *args)
os.exit(1)
def chomp(s: str) -> str:
for nl in ["\r\n", "\r", "\n"]:
if s.endswith(nl):
return s[: -len(nl)]
return s
def sysctl_subpath(name: str) -> str:
# "kernel.foo.bar" -> /proc/sys/kernel/foo/bar
return "sys/" + name.replace(".", "/")
PROCFS = ProcfsHandle.new(unmasked=True)
def sysctl_write(name: str, value: str) -> None:
subpath = sysctl_subpath(name)
with PROCFS.open(procfs.PROC_ROOT, subpath, "w") as f:
f.write(value)
def sysctl_read(name: str, *, value_only: bool = False) -> None:
subpath = sysctl_subpath(name)
with PROCFS.open(procfs.PROC_ROOT, subpath, "r") as f:
value = chomp(f.read())
if value_only:
print(f"{value}")
else:
print(f"{name} = {value}")
def main(*args):
import argparse
parser = argparse.ArgumentParser(
prog="sysctl.py",
description="A minimal implementation of sysctl(8) but using the libpathrs procfs API.",
)
parser.add_argument(
"-n",
"--values",
dest="value_only",
action="store_true",
help="print only values of the given variable(s)",
)
parser.add_argument(
"-w",
"--write",
action="store_true",
help="enable writing a value to a variable",
)
parser.add_argument(
"sysctls",
nargs="*",
metavar="variable[=value]",
help="sysctl variable name (such as 'kernel.overflowuid')",
)
args = parser.parse_args(args)
for sysctl in args.sysctls:
if "=" in sysctl:
if not args.write:
bail("you must pass -w to enable sysctl writing")
name, value = sysctl.split("=", maxsplit=1)
sysctl_write(name, value)
else:
sysctl_read(sysctl, value_only=args.value_only)
if __name__ == "__main__":
main(*sys.argv[1:])
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