用 Python 扫描失效的符号链接：区分断链、权限错误与循环链接

python3 --version
mkdir symlink-audit-demo
cd symlink-audit-demo
python3 - <<'PY_DATA'
from pathlib import Path
root = Path("sample")
(root / "nested").mkdir(parents=True)
(root / "data.txt").write_text("ready\n", encoding="utf-8")
(root / "good-file").symlink_to("data.txt")
(root / "good-dir").symlink_to("nested", target_is_directory=True)
(root / "missing-file").symlink_to("gone.txt")
(root / "missing-dir").symlink_to("gone-dir", target_is_directory=True)
PY_DATA

"""Read-only symlink audit for a quiet local directory. Python 3.9+."""
import argparse
import json
import os
from pathlib import Path
import stat


def audit(root):
    broken = []
    errors = []
    symlinks = 0

    def record_error(path, exc):
        errors.append({"path": str(path), "errno": exc.errno,
                       "message": str(exc)})

    def walk_error(exc):
        record_error(exc.filename or root, exc)

    for folder, dirs, names in os.walk(root, onerror=walk_error,
                                       followlinks=False):
        dirs.sort()
        for name in sorted(dirs + names):
            path = Path(folder) / name
            try:
                mode = path.lstat().st_mode
                if not stat.S_ISLNK(mode):
                    continue
                symlinks += 1
                target = os.readlink(path)
            except OSError as exc:
                record_error(path, exc)
                continue
            try:
                path.stat()
            except (FileNotFoundError, NotADirectoryError):
                broken.append({"path": str(path.relative_to(root)),
                               "target": target})
            except OSError as exc:
                record_error(path, exc)

    return {"root": str(root), "symlinks": symlinks,
            "broken": sorted(broken, key=lambda item: item["path"]),
            "errors": sorted(errors, key=lambda item: item["path"]),
            "complete": not errors}


def main(argv=None):
    parser = argparse.ArgumentParser(description=__doc__, allow_abbrev=False)
    parser.add_argument("directory", type=Path, help="directory to inspect")
    args = parser.parse_args(argv)
    try:
        root = args.directory.resolve(strict=True)
        if not stat.S_ISDIR(root.stat().st_mode):
            parser.error("directory must refer to a directory")
    except (OSError, RuntimeError) as exc:
        parser.error(str(exc))

    report = audit(root)
    print(json.dumps(report, indent=2, sort_keys=True))
    if report["errors"]:
        return 2
    return 1 if report["broken"] else 0


if __name__ == "__main__":
    raise SystemExit(main())

python3 check_symlinks.py --help
if python3 check_symlinks.py sample > report.json; then
  scan_rc=0
else
  scan_rc=$?
fi
printf 'exit=%s\n' "$scan_rc"
python3 - <<'PY_CHECK'
import json
from pathlib import Path
report = json.loads(Path("report.json").read_text())
assert report["symlinks"] == 4
assert report["complete"] is True
assert report["errors"] == []
assert report["broken"] == [
    {"path": "missing-dir", "target": "gone-dir"},
    {"path": "missing-file", "target": "gone.txt"},
]
print(f"symlinks={report['symlinks']} broken={len(report['broken'])} complete={report['complete']}")
PY_CHECK

exit=1
symlinks=4 broken=2 complete=True

printf 'restored\n' > sample/gone.txt
mkdir sample/gone-dir
if python3 check_symlinks.py sample > repaired.json; then
  scan_rc=0
else
  scan_rc=$?
fi
printf 'exit=%s\n' "$scan_rc"

ln -s loop-b sample/loop-a
ln -s loop-a sample/loop-b
if python3 check_symlinks.py sample > loop-report.json; then
  scan_rc=0
else
  scan_rc=$?
fi
printf 'exit=%s\n' "$scan_rc"
python3 - <<'PY_LOOP'
import errno
import json
from pathlib import Path
report = json.loads(Path("loop-report.json").read_text())
assert report["complete"] is False
assert report["broken"] == []
assert len(report["errors"]) == 2
assert all(item["errno"] == errno.ELOOP for item in report["errors"])
print("loop errors=2 complete=False")
PY_LOOP

if /usr/bin/python3 /srv/tools/check_symlinks.py /srv/project/data > /srv/reports/symlinks.json; then
  scan_rc=0
else
  scan_rc=$?
fi
printf 'symlink audit exit=%s\n' "$scan_rc"
exit "$scan_rc"