diff options
Diffstat (limited to 'Lib/os.py')
| -rw-r--r-- | Lib/os.py | 103 |
1 files changed, 97 insertions, 6 deletions
@@ -24,6 +24,7 @@ and opendir), and leave all pathname manipulation to os.path #' import sys, errno +import stat as st _names = sys.builtin_module_names @@ -32,6 +33,9 @@ __all__ = ["altsep", "curdir", "pardir", "sep", "pathsep", "linesep", "defpath", "name", "path", "devnull", "SEEK_SET", "SEEK_CUR", "SEEK_END"] +def _exists(name): + return name in globals() + def _get_exports_list(module): try: return list(module.__all__) @@ -120,7 +124,12 @@ def _get_masked_mode(mode): umask(mask) return mode & ~mask -#' +def _are_same_file(stat1, stat2): + """Helper function that checks whether two stat results refer to the same + file. + """ + return (stat1.st_ino == stat2.st_ino and stat1.st_dev == stat2.st_dev) +# # Super directory utilities. # (Inspired by Eric Raymond; the doc strings are mostly his) @@ -151,7 +160,6 @@ def makedirs(name, mode=0o777, exist_ok=False): try: mkdir(name, mode) except OSError as e: - import stat as st if not (e.errno == errno.EEXIST and exist_ok and path.isdir(name) and st.S_IMODE(lstat(name).st_mode) == _get_masked_mode(mode)): raise @@ -298,6 +306,92 @@ def walk(top, topdown=True, onerror=None, followlinks=False): __all__.append("walk") +if _exists("openat"): + + def fwalk(top, topdown=True, onerror=None, followlinks=False): + """Directory tree generator. + + This behaves exactly like walk(), except that it yields a 4-tuple + + dirpath, dirnames, filenames, dirfd + + `dirpath`, `dirnames` and `filenames` are identical to walk() output, + and `dirfd` is a file descriptor referring to the directory `dirpath`. + + The advantage of walkfd() over walk() is that it's safe against symlink + races (when followlinks is False). + + Caution: + Since fwalk() yields file descriptors, those are only valid until the + next iteration step, so you should dup() them if you want to keep them + for a longer period. + + Example: + + import os + for root, dirs, files, rootfd in os.fwalk('python/Lib/email'): + print(root, "consumes", end="") + print(sum([os.fstatat(rootfd, name).st_size for name in files]), + end="") + print("bytes in", len(files), "non-directory files") + if 'CVS' in dirs: + dirs.remove('CVS') # don't visit CVS directories + """ + # Note: To guard against symlink races, we use the standard + # lstat()/open()/fstat() trick. + orig_st = lstat(top) + topfd = open(top, O_RDONLY) + try: + if (followlinks or (st.S_ISDIR(orig_st.st_mode) and + _are_same_file(orig_st, fstat(topfd)))): + for x in _fwalk(topfd, top, topdown, onerror, followlinks): + yield x + finally: + close(topfd) + + def _fwalk(topfd, toppath, topdown, onerror, followlinks): + # Note: This uses O(depth of the directory tree) file descriptors: if + # necessary, it can be adapted to only require O(1) FDs, see issue + # #13734. + + # whether to follow symlinks + flag = 0 if followlinks else AT_SYMLINK_NOFOLLOW + + names = flistdir(topfd) + dirs, nondirs = [], [] + for name in names: + # Here, we don't use AT_SYMLINK_NOFOLLOW to be consistent with + # walk() which reports symlinks to directories as directories. We do + # however check for symlinks before recursing into a subdirectory. + if st.S_ISDIR(fstatat(topfd, name).st_mode): + dirs.append(name) + else: + nondirs.append(name) + + if topdown: + yield toppath, dirs, nondirs, topfd + + for name in dirs: + try: + orig_st = fstatat(topfd, name, flag) + dirfd = openat(topfd, name, O_RDONLY) + except error as err: + if onerror is not None: + onerror(err) + return + try: + if followlinks or _are_same_file(orig_st, fstat(dirfd)): + dirpath = path.join(toppath, name) + for x in _fwalk(dirfd, dirpath, topdown, onerror, followlinks): + yield x + finally: + close(dirfd) + + if not topdown: + yield toppath, dirs, nondirs, topfd + + __all__.append("fwalk") + # Make sure os.environ exists, at least try: environ @@ -434,7 +528,7 @@ def get_exec_path(env=None): # Change environ to automatically call putenv(), unsetenv if they exist. -from _abcoll import MutableMapping # Can't use collections (bootstrap) +from collections.abc import MutableMapping class _Environ(MutableMapping): def __init__(self, data, encodekey, decodekey, encodevalue, decodevalue, putenv, unsetenv): @@ -598,9 +692,6 @@ def _fscodec(): fsencode, fsdecode = _fscodec() del _fscodec -def _exists(name): - return name in globals() - # Supply spawn*() (probably only for Unix) if _exists("fork") and not _exists("spawnv") and _exists("execv"): |