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Diffstat (limited to 'Doc/library/os.rst')
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diff --git a/Doc/library/os.rst b/Doc/library/os.rst index ebba21ac46..d7b98292ad 100644 --- a/Doc/library/os.rst +++ b/Doc/library/os.rst @@ -96,6 +96,13 @@ These functions and data items provide information and operate on the current process and user. +.. function:: ctermid() + + Return the filename corresponding to the controlling terminal of the process. + + Availability: Unix. + + .. data:: environ A :term:`mapping` object representing the string environment. For example, @@ -177,6 +184,28 @@ process and user. .. versionadded:: 3.2 +.. function:: getenv(key, default=None) + + Return the value of the environment variable *key* if it exists, or + *default* if it doesn't. *key*, *default* and the result are str. + + On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding` + and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you + would like to use a different encoding. + + Availability: most flavors of Unix, Windows. + + +.. function:: getenvb(key, default=None) + + Return the value of the environment variable *key* if it exists, or + *default* if it doesn't. *key*, *default* and the result are bytes. + + Availability: most flavors of Unix. + + .. versionadded:: 3.2 + + .. function:: get_exec_path(env=None) Returns the list of directories that will be searched for a named @@ -188,13 +217,6 @@ process and user. .. versionadded:: 3.2 -.. function:: ctermid() - - Return the filename corresponding to the controlling terminal of the process. - - Availability: Unix. - - .. function:: getegid() Return the effective group id of the current process. This corresponds to the @@ -221,13 +243,26 @@ process and user. Availability: Unix. +.. function:: getgrouplist(user, group) + + Return list of group ids that *user* belongs to. If *group* is not in the + list, it is included; typically, *group* is specified as the group ID + field from the password record for *user*. + + Availability: Unix. + + .. versionadded:: 3.3 + + .. function:: getgroups() Return list of supplemental group ids associated with the current process. Availability: Unix. - .. note:: On Mac OS X, :func:`getgroups` behavior differs somewhat from + .. note:: + + On Mac OS X, :func:`getgroups` behavior differs somewhat from other Unix platforms. If the Python interpreter was built with a deployment target of :const:`10.5` or earlier, :func:`getgroups` returns the list of effective group ids associated with the current user process; @@ -242,17 +277,6 @@ process and user. obtained with :func:`sysconfig.get_config_var`. -.. function:: initgroups(username, gid) - - Call the system initgroups() to initialize the group access list with all of - the groups of which the specified username is a member, plus the specified - group id. - - Availability: Unix. - - .. versionadded:: 3.2 - - .. function:: getlogin() Return the name of the user logged in on the controlling terminal of the @@ -297,11 +321,40 @@ process and user. the id returned is the one of the init process (1), on Windows it is still the same id, which may be already reused by another process. - Availability: Unix, Windows + Availability: Unix, Windows. .. versionchanged:: 3.2 Added support for Windows. + +.. function:: getpriority(which, who) + + .. index:: single: process; scheduling priority + + Get program scheduling priority. The value *which* is one of + :const:`PRIO_PROCESS`, :const:`PRIO_PGRP`, or :const:`PRIO_USER`, and *who* + is interpreted relative to *which* (a process identifier for + :const:`PRIO_PROCESS`, process group identifier for :const:`PRIO_PGRP`, and a + user ID for :const:`PRIO_USER`). A zero value for *who* denotes + (respectively) the calling process, the process group of the calling process, + or the real user ID of the calling process. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. data:: PRIO_PROCESS + PRIO_PGRP + PRIO_USER + + Parameters for the :func:`getpriority` and :func:`setpriority` functions. + + Availability: Unix. + + .. versionadded:: 3.3 + + .. function:: getresuid() Return a tuple (ruid, euid, suid) denoting the current process's @@ -331,24 +384,13 @@ process and user. Availability: Unix. -.. function:: getenv(key, default=None) - - Return the value of the environment variable *key* if it exists, or - *default* if it doesn't. *key*, *default* and the result are str. - - On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding` - and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you - would like to use a different encoding. - - Availability: most flavors of Unix, Windows. - - -.. function:: getenvb(key, default=None) +.. function:: initgroups(username, gid) - Return the value of the environment variable *key* if it exists, or - *default* if it doesn't. *key*, *default* and the result are bytes. + Call the system initgroups() to initialize the group access list with all of + the groups of which the specified username is a member, plus the specified + group id. - Availability: most flavors of Unix. + Availability: Unix. .. versionadded:: 3.2 @@ -410,7 +452,7 @@ process and user. .. function:: setpgrp() - Call the system call :c:func:`setpgrp` or :c:func:`setpgrp(0, 0)` depending on + Call the system call :c:func:`setpgrp` or ``setpgrp(0, 0)`` depending on which version is implemented (if any). See the Unix manual for the semantics. Availability: Unix. @@ -425,6 +467,25 @@ process and user. Availability: Unix. +.. function:: setpriority(which, who, priority) + + .. index:: single: process; scheduling priority + + Set program scheduling priority. The value *which* is one of + :const:`PRIO_PROCESS`, :const:`PRIO_PGRP`, or :const:`PRIO_USER`, and *who* + is interpreted relative to *which* (a process identifier for + :const:`PRIO_PROCESS`, process group identifier for :const:`PRIO_PGRP`, and a + user ID for :const:`PRIO_USER`). A zero value for *who* denotes + (respectively) the calling process, the process group of the calling process, + or the real user ID of the calling process. + *priority* is a value in the range -20 to 19. The default priority is 0; + lower priorities cause more favorable scheduling. + + Availability: Unix + + .. versionadded:: 3.3 + + .. function:: setregid(rgid, egid) Set the current process's real and effective group ids. @@ -492,7 +553,7 @@ process and user. .. data:: supports_bytes_environ - True if the native OS type of the environment is bytes (eg. False on + ``True`` if the native OS type of the environment is bytes (eg. ``False`` on Windows). .. versionadded:: 3.2 @@ -511,15 +572,31 @@ process and user. single: gethostname() (in module socket) single: gethostbyaddr() (in module socket) - Return a 5-tuple containing information identifying the current operating - system. The tuple contains 5 strings: ``(sysname, nodename, release, version, - machine)``. Some systems truncate the nodename to 8 characters or to the + Returns information identifying the current operating system. + The return value is an object with five attributes: + + * :attr:`sysname` - operating system name + * :attr:`nodename` - name of machine on network (implementation-defined) + * :attr:`release` - operating system release + * :attr:`version` - operating system version + * :attr:`machine` - hardware identifier + + For backwards compatibility, this object is also iterable, behaving + like a five-tuple containing :attr:`sysname`, :attr:`nodename`, + :attr:`release`, :attr:`version`, and :attr:`machine` + in that order. + + Some systems truncate :attr:`nodename` to 8 characters or to the leading component; a better way to get the hostname is :func:`socket.gethostname` or even ``socket.gethostbyaddr(socket.gethostname())``. Availability: recent flavors of Unix. + .. versionchanged:: 3.3 + Return type changed from a tuple to a tuple-like object + with named attributes. + .. function:: unsetenv(key) @@ -542,15 +619,16 @@ process and user. File Object Creation -------------------- -These functions create new :term:`file objects <file object>`. (See also :func:`open`.) +This function creates new :term:`file objects <file object>`. (See also +:func:`~os.open` for opening file descriptors.) .. function:: fdopen(fd, *args, **kwargs) - Return an open file object connected to the file descriptor *fd*. - This is an alias of :func:`open` and accepts the same arguments. - The only difference is that the first argument of :func:`fdopen` - must always be an integer. + Return an open file object connected to the file descriptor *fd*. This is an + alias of the :func:`open` built-in function and accepts the same arguments. + The only difference is that the first argument of :func:`fdopen` must always + be an integer. .. _os-fd-ops: @@ -567,11 +645,12 @@ process will then be assigned 3, 4, 5, and so forth. The name "file descriptor" is slightly deceptive; on Unix platforms, sockets and pipes are also referenced by file descriptors. -The :meth:`~file.fileno` method can be used to obtain the file descriptor +The :meth:`~io.IOBase.fileno` method can be used to obtain the file descriptor associated with a :term:`file object` when required. Note that using the file descriptor directly will bypass the file object methods, ignoring aspects such as internal buffering of data. + .. function:: close(fd) Close file descriptor *fd*. @@ -583,13 +662,13 @@ as internal buffering of data. This function is intended for low-level I/O and must be applied to a file descriptor as returned by :func:`os.open` or :func:`pipe`. To close a "file object" returned by the built-in function :func:`open` or by :func:`popen` or - :func:`fdopen`, use its :meth:`~file.close` method. + :func:`fdopen`, use its :meth:`~io.IOBase.close` method. .. function:: closerange(fd_low, fd_high) Close all file descriptors from *fd_low* (inclusive) to *fd_high* (exclusive), - ignoring errors. Equivalent to:: + ignoring errors. Equivalent to (but much faster than):: for fd in range(fd_low, fd_high): try: @@ -622,8 +701,9 @@ as internal buffering of data. .. function:: fchmod(fd, mode) - Change the mode of the file given by *fd* to the numeric *mode*. See the docs - for :func:`chmod` for possible values of *mode*. + Change the mode of the file given by *fd* to the numeric *mode*. See the + docs for :func:`chmod` for possible values of *mode*. As of Python 3.3, this + is equivalent to ``os.chmod(fd, mode)``. Availability: Unix. @@ -631,7 +711,9 @@ as internal buffering of data. .. function:: fchown(fd, uid, gid) Change the owner and group id of the file given by *fd* to the numeric *uid* - and *gid*. To leave one of the ids unchanged, set it to -1. + and *gid*. To leave one of the ids unchanged, set it to -1. See + :func:`chown`. As of Python 3.3, this is equivalent to ``os.chown(fd, uid, + gid)``. Availability: Unix. @@ -662,20 +744,24 @@ as internal buffering of data. included in ``pathconf_names``, an :exc:`OSError` is raised with :const:`errno.EINVAL` for the error number. + As of Python 3.3, this is equivalent to ``os.pathconf(fd, name)``. + Availability: Unix. .. function:: fstat(fd) - Return status for file descriptor *fd*, like :func:`~os.stat`. + Return status for file descriptor *fd*, like :func:`~os.stat`. As of Python + 3.3, this is equivalent to ``os.stat(fd)``. Availability: Unix, Windows. .. function:: fstatvfs(fd) - Return information about the filesystem containing the file associated with file - descriptor *fd*, like :func:`statvfs`. + Return information about the filesystem containing the file associated with + file descriptor *fd*, like :func:`statvfs`. As of Python 3.3, this is + equivalent to ``os.statvfs(fd)``. Availability: Unix. @@ -689,13 +775,14 @@ as internal buffering of data. ``f.flush()``, and then do ``os.fsync(f.fileno())``, to ensure that all internal buffers associated with *f* are written to disk. - Availability: Unix, and Windows. + Availability: Unix, Windows. .. function:: ftruncate(fd, length) - Truncate the file corresponding to file descriptor *fd*, so that it is at most - *length* bytes in size. + Truncate the file corresponding to file descriptor *fd*, so that it is at + most *length* bytes in size. As of Python 3.3, this is equivalent to + ``os.truncate(fd, length)``. Availability: Unix. @@ -705,15 +792,38 @@ as internal buffering of data. Return ``True`` if the file descriptor *fd* is open and connected to a tty(-like) device, else ``False``. + +.. function:: lockf(fd, cmd, len) + + Apply, test or remove a POSIX lock on an open file descriptor. + *fd* is an open file descriptor. + *cmd* specifies the command to use - one of :data:`F_LOCK`, :data:`F_TLOCK`, + :data:`F_ULOCK` or :data:`F_TEST`. + *len* specifies the section of the file to lock. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. data:: F_LOCK + F_TLOCK + F_ULOCK + F_TEST + + Flags that specify what action :func:`lockf` will take. + Availability: Unix. + .. versionadded:: 3.3 + .. function:: lseek(fd, pos, how) Set the current position of file descriptor *fd* to position *pos*, modified by *how*: :const:`SEEK_SET` or ``0`` to set the position relative to the beginning of the file; :const:`SEEK_CUR` or ``1`` to set it relative to the - current position; :const:`os.SEEK_END` or ``2`` to set it relative to the end of + current position; :const:`SEEK_END` or ``2`` to set it relative to the end of the file. Return the new cursor position in bytes, starting from the beginning. Availability: Unix, Windows. @@ -724,21 +834,29 @@ as internal buffering of data. SEEK_END Parameters to the :func:`lseek` function. Their values are 0, 1, and 2, - respectively. Availability: Windows, Unix. + respectively. + + Availability: Unix, Windows. + .. versionadded:: 3.3 + Some operating systems could support additional values, like + :data:`os.SEEK_HOLE` or :data:`os.SEEK_DATA`. -.. function:: open(file, flags[, mode]) + +.. function:: open(file, flags, mode=0o777, *, dir_fd=None) Open the file *file* and set various flags according to *flags* and possibly - its mode according to *mode*. The default *mode* is ``0o777`` (octal), and - the current umask value is first masked out. Return the file descriptor for - the newly opened file. + its mode according to *mode*. When computing *mode*, the current umask value + is first masked out. Return the file descriptor for the newly opened file. For a description of the flag and mode values, see the C run-time documentation; flag constants (like :const:`O_RDONLY` and :const:`O_WRONLY`) are defined in this module too (see :ref:`open-constants`). In particular, on Windows adding :const:`O_BINARY` is needed to open files in binary mode. + This function can support :ref:`paths relative to directory descriptors + <dir_fd>`. + Availability: Unix, Windows. .. note:: @@ -748,6 +866,9 @@ as internal buffering of data. :meth:`~file.read` and :meth:`~file.write` methods (and many more). To wrap a file descriptor in a file object, use :func:`fdopen`. + .. versionadded:: 3.3 + The *dir_fd* argument. + .. function:: openpty() @@ -768,6 +889,79 @@ as internal buffering of data. Availability: Unix, Windows. +.. function:: pipe2(flags) + + Create a pipe with *flags* set atomically. + *flags* can be constructed by ORing together one or more of these values: + :data:`O_NONBLOCK`, :data:`O_CLOEXEC`. + Return a pair of file descriptors ``(r, w)`` usable for reading and writing, + respectively. + + Availability: some flavors of Unix. + + .. versionadded:: 3.3 + + +.. function:: posix_fallocate(fd, offset, len) + + Ensures that enough disk space is allocated for the file specified by *fd* + starting from *offset* and continuing for *len* bytes. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. function:: posix_fadvise(fd, offset, len, advice) + + Announces an intention to access data in a specific pattern thus allowing + the kernel to make optimizations. + The advice applies to the region of the file specified by *fd* starting at + *offset* and continuing for *len* bytes. + *advice* is one of :data:`POSIX_FADV_NORMAL`, :data:`POSIX_FADV_SEQUENTIAL`, + :data:`POSIX_FADV_RANDOM`, :data:`POSIX_FADV_NOREUSE`, + :data:`POSIX_FADV_WILLNEED` or :data:`POSIX_FADV_DONTNEED`. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. data:: POSIX_FADV_NORMAL + POSIX_FADV_SEQUENTIAL + POSIX_FADV_RANDOM + POSIX_FADV_NOREUSE + POSIX_FADV_WILLNEED + POSIX_FADV_DONTNEED + + Flags that can be used in *advice* in :func:`posix_fadvise` that specify + the access pattern that is likely to be used. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. function:: pread(fd, buffersize, offset) + + Read from a file descriptor, *fd*, at a position of *offset*. It will read up + to *buffersize* number of bytes. The file offset remains unchanged. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. function:: pwrite(fd, string, offset) + + Write *string* to a file descriptor, *fd*, from *offset*, leaving the file + offset unchanged. + + Availability: Unix. + + .. versionadded:: 3.3 + + .. function:: read(fd, n) Read at most *n* bytes from file descriptor *fd*. Return a bytestring containing the @@ -779,10 +973,64 @@ as internal buffering of data. .. note:: This function is intended for low-level I/O and must be applied to a file - descriptor as returned by :func:`os.open` or :func:`pipe`. To read a "file object" - returned by the built-in function :func:`open` or by :func:`popen` or - :func:`fdopen`, or :data:`sys.stdin`, use its :meth:`~file.read` or - :meth:`~file.readline` methods. + descriptor as returned by :func:`os.open` or :func:`pipe`. To read a + "file object" returned by the built-in function :func:`open` or by + :func:`popen` or :func:`fdopen`, or :data:`sys.stdin`, use its + :meth:`~file.read` or :meth:`~file.readline` methods. + + +.. function:: sendfile(out, in, offset, nbytes) + sendfile(out, in, offset, nbytes, headers=None, trailers=None, flags=0) + + Copy *nbytes* bytes from file descriptor *in* to file descriptor *out* + starting at *offset*. + Return the number of bytes sent. When EOF is reached return 0. + + The first function notation is supported by all platforms that define + :func:`sendfile`. + + On Linux, if *offset* is given as ``None``, the bytes are read from the + current position of *in* and the position of *in* is updated. + + The second case may be used on Mac OS X and FreeBSD where *headers* and + *trailers* are arbitrary sequences of buffers that are written before and + after the data from *in* is written. It returns the same as the first case. + + On Mac OS X and FreeBSD, a value of 0 for *nbytes* specifies to send until + the end of *in* is reached. + + All platforms support sockets as *out* file descriptor, and some platforms + allow other types (e.g. regular file, pipe) as well. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. data:: SF_NODISKIO + SF_MNOWAIT + SF_SYNC + + Parameters to the :func:`sendfile` function, if the implementation supports + them. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. function:: readv(fd, buffers) + + Read from a file descriptor *fd* into a number of mutable :term:`bytes-like + objects <bytes-like object>` *buffers*. :func:`~os.readv` will transfer data + into each buffer until it is full and then move on to the next buffer in the + sequence to hold the rest of the data. :func:`~os.readv` returns the total + number of bytes read (which may be less than the total capacity of all the + objects). + + Availability: Unix. + + .. versionadded:: 3.3 .. function:: tcgetpgrp(fd) @@ -826,6 +1074,18 @@ as internal buffering of data. :meth:`~file.write` method. +.. function:: writev(fd, buffers) + + Write the contents of *buffers* to file descriptor *fd*. *buffers* must be a + sequence of :term:`bytes-like objects <bytes-like object>`. + :func:`~os.writev` writes the contents of each object to the file descriptor + and returns the total number of bytes written. + + Availability: Unix. + + .. versionadded:: 3.3 + + .. _open-constants: ``open()`` flag constants @@ -857,9 +1117,12 @@ or `the MSDN <http://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Window O_NOCTTY O_SHLOCK O_EXLOCK + O_CLOEXEC These constants are only available on Unix. + .. versionchanged:: 3.3 + Add :data:`O_CLOEXEC` constant. .. data:: O_BINARY O_NOINHERIT @@ -882,12 +1145,106 @@ or `the MSDN <http://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Window the C library. +.. data:: RTLD_LAZY + RTLD_NOW + RTLD_GLOBAL + RTLD_LOCAL + RTLD_NODELETE + RTLD_NOLOAD + RTLD_DEEPBIND + + See the Unix manual page :manpage:`dlopen(3)`. + + .. versionadded:: 3.3 + + +.. _terminal-size: + +Querying the size of a terminal +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. versionadded:: 3.3 + +.. function:: get_terminal_size(fd=STDOUT_FILENO) + + Return the size of the terminal window as ``(columns, lines)``, + tuple of type :class:`terminal_size`. + + The optional argument ``fd`` (default ``STDOUT_FILENO``, or standard + output) specifies which file descriptor should be queried. + + If the file descriptor is not connected to a terminal, an :exc:`OSError` + is raised. + + :func:`shutil.get_terminal_size` is the high-level function which + should normally be used, ``os.get_terminal_size`` is the low-level + implementation. + + Availability: Unix, Windows. + +.. class:: terminal_size + + A subclass of tuple, holding ``(columns, lines)`` of the terminal window size. + + .. attribute:: columns + + Width of the terminal window in characters. + + .. attribute:: lines + + Height of the terminal window in characters. + + .. _os-file-dir: Files and Directories --------------------- -.. function:: access(path, mode) +On some Unix platforms, many of these functions support one or more of these +features: + +.. _path_fd: + +* **specifying a file descriptor:** + For some functions, the *path* argument can be not only a string giving a path + name, but also a file descriptor. The function will then operate on the file + referred to by the descriptor. (For POSIX systems, Python will call the + ``f...`` version of the function.) + + You can check whether or not *path* can be specified as a file descriptor on + your platform using :data:`os.supports_fd`. If it is unavailable, using it + will raise a :exc:`NotImplementedError`. + + If the function also supports *dir_fd* or *follow_symlinks* arguments, it is + an error to specify one of those when supplying *path* as a file descriptor. + +.. _dir_fd: + +* **paths relative to directory descriptors:** If *dir_fd* is not ``None``, it + should be a file descriptor referring to a directory, and the path to operate + on should be relative; path will then be relative to that directory. If the + path is absolute, *dir_fd* is ignored. (For POSIX systems, Python will call + the ``...at`` or ``f...at`` version of the function.) + + You can check whether or not *dir_fd* is supported on your platform using + :data:`os.supports_dir_fd`. If it is unavailable, using it will raise a + :exc:`NotImplementedError`. + +.. _follow_symlinks: + +* **not following symlinks:** If *follow_symlinks* is + ``False``, and the last element of the path to operate on is a symbolic link, + the function will operate on the symbolic link itself instead of the file the + link points to. (For POSIX systems, Python will call the ``l...`` version of + the function.) + + You can check whether or not *follow_symlinks* is supported on your platform + using :data:`os.supports_follow_symlinks`. If it is unavailable, using it + will raise a :exc:`NotImplementedError`. + + + +.. function:: access(path, mode, *, dir_fd=None, effective_ids=False, follow_symlinks=True) Use the real uid/gid to test for access to *path*. Note that most operations will use the effective uid/gid, therefore this routine can be used in a @@ -898,6 +1255,15 @@ Files and Directories :const:`False` if not. See the Unix man page :manpage:`access(2)` for more information. + This function can support specifying :ref:`paths relative to directory + descriptors <dir_fd>` and :ref:`not following symlinks <follow_symlinks>`. + + If *effective_ids* is ``True``, :func:`access` will perform its access + checks using the effective uid/gid instead of the real uid/gid. + *effective_ids* may not be supported on your platform; you can check whether + or not it is available using :data:`os.supports_effective_ids`. If it is + unavailable, using it will raise a :exc:`NotImplementedError`. + Availability: Unix, Windows. .. note:: @@ -917,11 +1283,8 @@ Files and Directories try: fp = open("myfile") - except IOError as e: - if e.errno == errno.EACCES: - return "some default data" - # Not a permission error. - raise + except PermissionError: + return "some default data" else: with fp: return fp.read() @@ -932,29 +1295,18 @@ Files and Directories succeed, particularly for operations on network filesystems which may have permissions semantics beyond the usual POSIX permission-bit model. + .. versionchanged:: 3.3 + Added the *dir_fd*, *effective_ids*, and *follow_symlinks* parameters. -.. data:: F_OK - - Value to pass as the *mode* parameter of :func:`access` to test the existence of - *path*. - - -.. data:: R_OK - - Value to include in the *mode* parameter of :func:`access` to test the - readability of *path*. - - -.. data:: W_OK - Value to include in the *mode* parameter of :func:`access` to test the - writability of *path*. - - -.. data:: X_OK +.. data:: F_OK + R_OK + W_OK + X_OK - Value to include in the *mode* parameter of :func:`access` to determine if - *path* can be executed. + Values to pass as the *mode* parameter of :func:`access` to test the + existence, readability, writability and executability of *path*, + respectively. .. function:: chdir(path) @@ -963,33 +1315,17 @@ Files and Directories Change the current working directory to *path*. - Availability: Unix, Windows. - - -.. function:: fchdir(fd) - - Change the current working directory to the directory represented by the file - descriptor *fd*. The descriptor must refer to an opened directory, not an open - file. - - Availability: Unix. - - -.. function:: getcwd() - - Return a string representing the current working directory. + This function can support :ref:`specifying a file descriptor <path_fd>`. The + descriptor must refer to an opened directory, not an open file. Availability: Unix, Windows. + .. versionadded:: 3.3 + Added support for specifying *path* as a file descriptor + on some platforms. -.. function:: getcwdb() - - Return a bytestring representing the current working directory. - - Availability: Unix, Windows. - -.. function:: chflags(path, flags) +.. function:: chflags(path, flags, *, follow_symlinks=True) Set the flags of *path* to the numeric *flags*. *flags* may take a combination (bitwise OR) of the following values (as defined in the :mod:`stat` module): @@ -1007,16 +1343,15 @@ Files and Directories * :data:`stat.SF_NOUNLINK` * :data:`stat.SF_SNAPSHOT` - Availability: Unix. - + This function can support :ref:`not following symlinks <follow_symlinks>`. -.. function:: chroot(path) + Availability: Unix. - Change the root directory of the current process to *path*. Availability: - Unix. + .. versionadded:: 3.3 + The *follow_symlinks* argument. -.. function:: chmod(path, mode) +.. function:: chmod(path, mode, *, dir_fd=None, follow_symlinks=True) Change the mode of *path* to the numeric *mode*. *mode* may take one of the following values (as defined in the :mod:`stat` module) or bitwise ORed @@ -1042,28 +1377,77 @@ Files and Directories * :data:`stat.S_IWOTH` * :data:`stat.S_IXOTH` + This function can support :ref:`specifying a file descriptor <path_fd>`, + :ref:`paths relative to directory descriptors <dir_fd>` and :ref:`not + following symlinks <follow_symlinks>`. + Availability: Unix, Windows. .. note:: - Although Windows supports :func:`chmod`, you can only set the file's read-only - flag with it (via the ``stat.S_IWRITE`` and ``stat.S_IREAD`` - constants or a corresponding integer value). All other bits are - ignored. + Although Windows supports :func:`chmod`, you can only set the file's + read-only flag with it (via the ``stat.S_IWRITE`` and ``stat.S_IREAD`` + constants or a corresponding integer value). All other bits are ignored. + + .. versionadded:: 3.3 + Added support for specifying *path* as an open file descriptor, + and the *dir_fd* and *follow_symlinks* arguments. + + +.. function:: chown(path, uid, gid, *, dir_fd=None, follow_symlinks=True) + + Change the owner and group id of *path* to the numeric *uid* and *gid*. To + leave one of the ids unchanged, set it to -1. + + This function can support :ref:`specifying a file descriptor <path_fd>`, + :ref:`paths relative to directory descriptors <dir_fd>` and :ref:`not + following symlinks <follow_symlinks>`. + + See :func:`shutil.chown` for a higher-level function that accepts names in + addition to numeric ids. + + Availability: Unix. + + .. versionadded:: 3.3 + Added support for specifying an open file descriptor for *path*, + and the *dir_fd* and *follow_symlinks* arguments. + + +.. function:: chroot(path) + + Change the root directory of the current process to *path*. + + Availability: Unix. -.. function:: chown(path, uid, gid) +.. function:: fchdir(fd) - Change the owner and group id of *path* to the numeric *uid* and *gid*. To leave - one of the ids unchanged, set it to -1. + Change the current working directory to the directory represented by the file + descriptor *fd*. The descriptor must refer to an opened directory, not an + open file. As of Python 3.3, this is equivalent to ``os.chdir(fd)``. Availability: Unix. +.. function:: getcwd() + + Return a string representing the current working directory. + + Availability: Unix, Windows. + + +.. function:: getcwdb() + + Return a bytestring representing the current working directory. + + Availability: Unix, Windows. + + .. function:: lchflags(path, flags) - Set the flags of *path* to the numeric *flags*, like :func:`chflags`, but do not - follow symbolic links. + Set the flags of *path* to the numeric *flags*, like :func:`chflags`, but do + not follow symbolic links. As of Python 3.3, this is equivalent to + ``os.chflags(path, flags, follow_symlinks=False)``. Availability: Unix. @@ -1071,110 +1455,101 @@ Files and Directories .. function:: lchmod(path, mode) Change the mode of *path* to the numeric *mode*. If path is a symlink, this - affects the symlink rather than the target. See the docs for :func:`chmod` - for possible values of *mode*. + affects the symlink rather than the target. See the docs for :func:`chmod` + for possible values of *mode*. As of Python 3.3, this is equivalent to + ``os.chmod(path, mode, follow_symlinks=False)``. Availability: Unix. .. function:: lchown(path, uid, gid) - Change the owner and group id of *path* to the numeric *uid* and *gid*. This - function will not follow symbolic links. + Change the owner and group id of *path* to the numeric *uid* and *gid*. This + function will not follow symbolic links. As of Python 3.3, this is equivalent + to ``os.chown(path, uid, gid, follow_symlinks=False)``. Availability: Unix. -.. function:: link(source, link_name) +.. function:: link(src, dst, *, src_dir_fd=None, dst_dir_fd=None, follow_symlinks=True) + + Create a hard link pointing to *src* named *dst*. - Create a hard link pointing to *source* named *link_name*. + This function can support specifying *src_dir_fd* and/or *dst_dir_fd* to + supply :ref:`paths relative to directory descriptors <dir_fd>`, and :ref:`not + following symlinks <follow_symlinks>`. Availability: Unix, Windows. .. versionchanged:: 3.2 Added Windows support. + .. versionadded:: 3.3 + Added the *src_dir_fd*, *dst_dir_fd*, and *follow_symlinks* arguments. + .. function:: listdir(path='.') Return a list containing the names of the entries in the directory given by - *path* (default: ``'.'``). The list is in arbitrary order. It does not include the special + *path*. The list is in arbitrary order, and does not include the special entries ``'.'`` and ``'..'`` even if they are present in the directory. - This function can be called with a bytes or string argument, and returns - filenames of the same datatype. + *path* may be either of type ``str`` or of type ``bytes``. If *path* + is of type ``bytes``, the filenames returned will also be of type ``bytes``; + in all other circumstances, they will be of type ``str``. + + This function can also support :ref:`specifying a file descriptor + <path_fd>`; the file descriptor must refer to a directory. + + .. note:: + To encode ``str`` filenames to ``bytes``, use :func:`~os.fsencode`. Availability: Unix, Windows. .. versionchanged:: 3.2 The *path* parameter became optional. -.. function:: lstat(path) + .. versionadded:: 3.3 + Added support for specifying an open file descriptor for *path*. + + +.. function:: lstat(path, *, dir_fd=None) Perform the equivalent of an :c:func:`lstat` system call on the given path. Similar to :func:`~os.stat`, but does not follow symbolic links. On platforms that do not support symbolic links, this is an alias for - :func:`~os.stat`. + :func:`~os.stat`. As of Python 3.3, this is equivalent to ``os.stat(path, + dir_fd=dir_fd, follow_symlinks=False)``. + + This function can also support :ref:`paths relative to directory descriptors + <dir_fd>`. .. versionchanged:: 3.2 Added support for Windows 6.0 (Vista) symbolic links. + .. versionchanged:: 3.3 + Added the *dir_fd* parameter. -.. function:: mkfifo(path[, mode]) - - Create a FIFO (a named pipe) named *path* with numeric mode *mode*. The - default *mode* is ``0o666`` (octal). The current umask value is first masked - out from the mode. - - FIFOs are pipes that can be accessed like regular files. FIFOs exist until they - are deleted (for example with :func:`os.unlink`). Generally, FIFOs are used as - rendezvous between "client" and "server" type processes: the server opens the - FIFO for reading, and the client opens it for writing. Note that :func:`mkfifo` - doesn't open the FIFO --- it just creates the rendezvous point. - - Availability: Unix. - - -.. function:: mknod(filename[, mode=0o600[, device=0]]) - - Create a filesystem node (file, device special file or named pipe) named - *filename*. *mode* specifies both the permissions to use and the type of node - to be created, being combined (bitwise OR) with one of ``stat.S_IFREG``, - ``stat.S_IFCHR``, ``stat.S_IFBLK``, and ``stat.S_IFIFO`` (those constants are - available in :mod:`stat`). For ``stat.S_IFCHR`` and ``stat.S_IFBLK``, - *device* defines the newly created device special file (probably using - :func:`os.makedev`), otherwise it is ignored. - - -.. function:: major(device) - - Extract the device major number from a raw device number (usually the - :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`). - - -.. function:: minor(device) - - Extract the device minor number from a raw device number (usually the - :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`). - - -.. function:: makedev(major, minor) - Compose a raw device number from the major and minor device numbers. +.. function:: mkdir(path, mode=0o777, *, dir_fd=None) + Create a directory named *path* with numeric mode *mode*. -.. function:: mkdir(path[, mode]) + On some systems, *mode* is ignored. Where it is used, the current umask + value is first masked out. If the directory already exists, :exc:`OSError` + is raised. - Create a directory named *path* with numeric mode *mode*. The default *mode* - is ``0o777`` (octal). On some systems, *mode* is ignored. Where it is used, - the current umask value is first masked out. If the directory already - exists, :exc:`OSError` is raised. + This function can also support :ref:`paths relative to directory descriptors + <dir_fd>`. It is also possible to create temporary directories; see the :mod:`tempfile` module's :func:`tempfile.mkdtemp` function. Availability: Unix, Windows. + .. versionadded:: 3.3 + The *dir_fd* argument. + .. function:: makedirs(path, mode=0o777, exist_ok=False) @@ -1201,12 +1576,66 @@ Files and Directories .. versionadded:: 3.2 The *exist_ok* parameter. - .. versionchanged:: 3.2.6 + .. versionchanged:: 3.3.6 - Before Python 3.2.6, if *exist_ok* was ``True`` and the directory existed, + Before Python 3.3.6, if *exist_ok* was ``True`` and the directory existed, :func:`makedirs` would still raise an error if *mode* did not match the mode of the existing directory. Since this behavior was impossible to - implement safely, it was removed in Python 3.2.6. See :issue:`21082`. + implement safely, it was removed in Python 3.3.6. See :issue:`21082`. + + +.. function:: mkfifo(path, mode=0o666, *, dir_fd=None) + + Create a FIFO (a named pipe) named *path* with numeric mode *mode*. + The current umask value is first masked out from the mode. + + This function can also support :ref:`paths relative to directory descriptors + <dir_fd>`. + + FIFOs are pipes that can be accessed like regular files. FIFOs exist until they + are deleted (for example with :func:`os.unlink`). Generally, FIFOs are used as + rendezvous between "client" and "server" type processes: the server opens the + FIFO for reading, and the client opens it for writing. Note that :func:`mkfifo` + doesn't open the FIFO --- it just creates the rendezvous point. + + Availability: Unix. + + .. versionadded:: 3.3 + The *dir_fd* argument. + + +.. function:: mknod(filename, mode=0o600, device=0, *, dir_fd=None) + + Create a filesystem node (file, device special file or named pipe) named + *filename*. *mode* specifies both the permissions to use and the type of node + to be created, being combined (bitwise OR) with one of ``stat.S_IFREG``, + ``stat.S_IFCHR``, ``stat.S_IFBLK``, and ``stat.S_IFIFO`` (those constants are + available in :mod:`stat`). For ``stat.S_IFCHR`` and ``stat.S_IFBLK``, + *device* defines the newly created device special file (probably using + :func:`os.makedev`), otherwise it is ignored. + + This function can also support :ref:`paths relative to directory descriptors + <dir_fd>`. + + .. versionadded:: 3.3 + The *dir_fd* argument. + + +.. function:: major(device) + + Extract the device major number from a raw device number (usually the + :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`). + + +.. function:: minor(device) + + Extract the device minor number from a raw device number (usually the + :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`). + + +.. function:: makedev(major, minor) + + Compose a raw device number from the major and minor device numbers. .. function:: pathconf(path, name) @@ -1224,6 +1653,9 @@ Files and Directories included in ``pathconf_names``, an :exc:`OSError` is raised with :const:`errno.EINVAL` for the error number. + This function can support :ref:`specifying a file descriptor + <path_fd>`. + Availability: Unix. @@ -1231,38 +1663,53 @@ Files and Directories Dictionary mapping names accepted by :func:`pathconf` and :func:`fpathconf` to the integer values defined for those names by the host operating system. This - can be used to determine the set of names known to the system. Availability: - Unix. + can be used to determine the set of names known to the system. + + Availability: Unix. -.. function:: readlink(path) +.. function:: readlink(path, *, dir_fd=None) Return a string representing the path to which the symbolic link points. The - result may be either an absolute or relative pathname; if it is relative, it may - be converted to an absolute pathname using ``os.path.join(os.path.dirname(path), - result)``. + result may be either an absolute or relative pathname; if it is relative, it + may be converted to an absolute pathname using + ``os.path.join(os.path.dirname(path), result)``. If the *path* is a string object, the result will also be a string object, and the call may raise an UnicodeDecodeError. If the *path* is a bytes object, the result will be a bytes object. + This function can also support :ref:`paths relative to directory descriptors + <dir_fd>`. + Availability: Unix, Windows .. versionchanged:: 3.2 Added support for Windows 6.0 (Vista) symbolic links. + .. versionadded:: 3.3 + The *dir_fd* argument. + -.. function:: remove(path) +.. function:: remove(path, *, dir_fd=None) Remove (delete) the file *path*. If *path* is a directory, :exc:`OSError` is - raised; see :func:`rmdir` below to remove a directory. This is identical to - the :func:`unlink` function documented below. On Windows, attempting to - remove a file that is in use causes an exception to be raised; on Unix, the - directory entry is removed but the storage allocated to the file is not made - available until the original file is no longer in use. + raised. Use :func:`rmdir` to remove directories. + + This function can support :ref:`paths relative to directory descriptors + <dir_fd>`. + + On Windows, attempting to remove a file that is in use causes an exception to + be raised; on Unix, the directory entry is removed but the storage allocated + to the file is not made available until the original file is no longer in use. + + This function is identical to :func:`unlink`. Availability: Unix, Windows. + .. versionadded:: 3.3 + The *dir_fd* argument. + .. function:: removedirs(path) @@ -1278,7 +1725,7 @@ Files and Directories successfully removed. -.. function:: rename(src, dst) +.. function:: rename(src, dst, *, src_dir_fd=None, dst_dir_fd=None) Rename the file or directory *src* to *dst*. If *dst* is a directory, :exc:`OSError` will be raised. On Unix, if *dst* exists and is a file, it will @@ -1286,11 +1733,18 @@ Files and Directories Unix flavors if *src* and *dst* are on different filesystems. If successful, the renaming will be an atomic operation (this is a POSIX requirement). On Windows, if *dst* already exists, :exc:`OSError` will be raised even if it is a - file; there may be no way to implement an atomic rename when *dst* names an - existing file. + file. + + This function can support specifying *src_dir_fd* and/or *dst_dir_fd* to + supply :ref:`paths relative to directory descriptors <dir_fd>`. + + If you want cross-platform overwriting of the destination, use :func:`replace`. Availability: Unix, Windows. + .. versionadded:: 3.3 + The *src_dir_fd* and *dst_dir_fd* arguments. + .. function:: renames(old, new) @@ -1305,22 +1759,46 @@ Files and Directories permissions needed to remove the leaf directory or file. -.. function:: rmdir(path) +.. function:: replace(src, dst, *, src_dir_fd=None, dst_dir_fd=None) + + Rename the file or directory *src* to *dst*. If *dst* is a directory, + :exc:`OSError` will be raised. If *dst* exists and is a file, it will + be replaced silently if the user has permission. The operation may fail + if *src* and *dst* are on different filesystems. If successful, + the renaming will be an atomic operation (this is a POSIX requirement). + + This function can support specifying *src_dir_fd* and/or *dst_dir_fd* to + supply :ref:`paths relative to directory descriptors <dir_fd>`. + + Availability: Unix, Windows. + + .. versionadded:: 3.3 + + +.. function:: rmdir(path, *, dir_fd=None) Remove (delete) the directory *path*. Only works when the directory is empty, otherwise, :exc:`OSError` is raised. In order to remove whole directory trees, :func:`shutil.rmtree` can be used. + This function can support :ref:`paths relative to directory descriptors + <dir_fd>`. + Availability: Unix, Windows. + .. versionadded:: 3.3 + The *dir_fd* parameter. -.. function:: stat(path) + +.. function:: stat(path, *, dir_fd=None, follow_symlinks=True) Perform the equivalent of a :c:func:`stat` system call on the given path. - (This function follows symlinks; to stat a symlink use :func:`lstat`.) + *path* may be specified as either a string or as an open file descriptor. + (This function normally follows symlinks; to stat a symlink add the argument + ``follow_symlinks=False``, or use :func:`lstat`.) - The return value is an object whose attributes correspond to the members - of the :c:type:`stat` structure, namely: + The return value is an object whose attributes correspond roughly + to the members of the :c:type:`stat` structure, namely: * :attr:`st_mode` - protection bits, * :attr:`st_ino` - inode number, @@ -1329,16 +1807,24 @@ Files and Directories * :attr:`st_uid` - user id of owner, * :attr:`st_gid` - group id of owner, * :attr:`st_size` - size of file, in bytes, - * :attr:`st_atime` - time of most recent access, - * :attr:`st_mtime` - time of most recent content modification, - * :attr:`st_ctime` - platform dependent; time of most recent metadata change on - Unix, or the time of creation on Windows) + * :attr:`st_atime` - time of most recent access expressed in seconds, + * :attr:`st_mtime` - time of most recent content modification + expressed in seconds, + * :attr:`st_ctime` - platform dependent; time of most recent metadata + change on Unix, or the time of creation on Windows, expressed in seconds + * :attr:`st_atime_ns` - time of most recent access + expressed in nanoseconds as an integer, + * :attr:`st_mtime_ns` - time of most recent content modification + expressed in nanoseconds as an integer, + * :attr:`st_ctime_ns` - platform dependent; time of most recent metadata + change on Unix, or the time of creation on Windows, + expressed in nanoseconds as an integer On some Unix systems (such as Linux), the following attributes may also be available: - * :attr:`st_blocks` - number of blocks allocated for file - * :attr:`st_blksize` - filesystem blocksize + * :attr:`st_blocks` - number of 512-byte blocks allocated for file + * :attr:`st_blksize` - filesystem blocksize for efficient file system I/O * :attr:`st_rdev` - type of device if an inode device * :attr:`st_flags` - user defined flags for file @@ -1362,13 +1848,25 @@ Files and Directories or FAT32 file systems, :attr:`st_mtime` has 2-second resolution, and :attr:`st_atime` has only 1-day resolution. See your operating system documentation for details. - - For backward compatibility, the return value of :func:`~os.stat` is also accessible - as a tuple of at least 10 integers giving the most important (and portable) - members of the :c:type:`stat` structure, in the order :attr:`st_mode`, - :attr:`st_ino`, :attr:`st_dev`, :attr:`st_nlink`, :attr:`st_uid`, - :attr:`st_gid`, :attr:`st_size`, :attr:`st_atime`, :attr:`st_mtime`, - :attr:`st_ctime`. More items may be added at the end by some implementations. + Similarly, although :attr:`st_atime_ns`, :attr:`st_mtime_ns`, + and :attr:`st_ctime_ns` are always expressed in nanoseconds, many + systems do not provide nanosecond precision. On systems that do + provide nanosecond precision, the floating-point object used to + store :attr:`st_atime`, :attr:`st_mtime`, and :attr:`st_ctime` + cannot preserve all of it, and as such will be slightly inexact. + If you need the exact timestamps you should always use + :attr:`st_atime_ns`, :attr:`st_mtime_ns`, and :attr:`st_ctime_ns`. + + For backward compatibility, the return value of :func:`~os.stat` is also + accessible as a tuple of at least 10 integers giving the most important (and + portable) members of the :c:type:`stat` structure, in the order + :attr:`st_mode`, :attr:`st_ino`, :attr:`st_dev`, :attr:`st_nlink`, + :attr:`st_uid`, :attr:`st_gid`, :attr:`st_size`, :attr:`st_atime`, + :attr:`st_mtime`, :attr:`st_ctime`. More items may be added at the end by + some implementations. + + This function can support :ref:`specifying a file descriptor <path_fd>` and + :ref:`not following symlinks <follow_symlinks>`. .. index:: module: stat @@ -1389,6 +1887,12 @@ Files and Directories Availability: Unix, Windows. + .. versionadded:: 3.3 + Added the *dir_fd* and *follow_symlinks* arguments, + specifying a file descriptor instead of a path, + and the :attr:`st_atime_ns`, :attr:`st_mtime_ns`, + and :attr:`st_ctime_ns` members. + .. function:: stat_float_times([newvalue]) @@ -1414,6 +1918,8 @@ Files and Directories are processed, this application should turn the feature off until the library has been corrected. + .. deprecated:: 3.3 + .. function:: statvfs(path) @@ -1429,36 +1935,122 @@ Files and Directories read-only, and if :const:`ST_NOSUID` is set, the semantics of setuid/setgid bits are disabled or not supported. + This function can support :ref:`specifying a file descriptor <path_fd>`. + .. versionchanged:: 3.2 The :const:`ST_RDONLY` and :const:`ST_NOSUID` constants were added. Availability: Unix. + .. versionadded:: 3.3 + Added support for specifying an open file descriptor for *path*. -.. function:: symlink(source, link_name) - symlink(source, link_name, target_is_directory=False) - Create a symbolic link pointing to *source* named *link_name*. +.. data:: supports_dir_fd + + A :class:`~collections.abc.Set` object indicating which functions in the + :mod:`os` module permit use of their *dir_fd* parameter. Different platforms + provide different functionality, and an option that might work on one might + be unsupported on another. For consistency's sakes, functions that support + *dir_fd* always allow specifying the parameter, but will raise an exception + if the functionality is not actually available. + + To check whether a particular function permits use of its *dir_fd* + parameter, use the ``in`` operator on ``supports_dir_fd``. As an example, + this expression determines whether the *dir_fd* parameter of :func:`os.stat` + is locally available:: + + os.stat in os.supports_dir_fd + + Currently *dir_fd* parameters only work on Unix platforms; none of them work + on Windows. + + .. versionadded:: 3.3 + + +.. data:: supports_effective_ids + + A :class:`~collections.abc.Set` object indicating which functions in the + :mod:`os` module permit use of the *effective_ids* parameter for + :func:`os.access`. If the local platform supports it, the collection will + contain :func:`os.access`, otherwise it will be empty. + + To check whether you can use the *effective_ids* parameter for + :func:`os.access`, use the ``in`` operator on ``supports_dir_fd``, like so:: + + os.access in os.supports_effective_ids + + Currently *effective_ids* only works on Unix platforms; it does not work on + Windows. + + .. versionadded:: 3.3 + + +.. data:: supports_fd + + A :class:`~collections.abc.Set` object indicating which functions in the + :mod:`os` module permit specifying their *path* parameter as an open file + descriptor. Different platforms provide different functionality, and an + option that might work on one might be unsupported on another. For + consistency's sakes, functions that support *fd* always allow specifying + the parameter, but will raise an exception if the functionality is not + actually available. + + To check whether a particular function permits specifying an open file + descriptor for its *path* parameter, use the ``in`` operator on + ``supports_fd``. As an example, this expression determines whether + :func:`os.chdir` accepts open file descriptors when called on your local + platform:: + + os.chdir in os.supports_fd - On Windows, symlink version takes an additional optional parameter, - *target_is_directory*, which defaults to ``False``. + .. versionadded:: 3.3 - On Windows, a symlink represents a file or a directory, and does not morph to - the target dynamically. If *target_is_directory* is set to ``True``, the - symlink will be created as a directory symlink, otherwise as a file symlink - (the default). + +.. data:: supports_follow_symlinks + + A :class:`~collections.abc.Set` object indicating which functions in the + :mod:`os` module permit use of their *follow_symlinks* parameter. Different + platforms provide different functionality, and an option that might work on + one might be unsupported on another. For consistency's sakes, functions that + support *follow_symlinks* always allow specifying the parameter, but will + raise an exception if the functionality is not actually available. + + To check whether a particular function permits use of its *follow_symlinks* + parameter, use the ``in`` operator on ``supports_follow_symlinks``. As an + example, this expression determines whether the *follow_symlinks* parameter + of :func:`os.stat` is locally available:: + + os.stat in os.supports_follow_symlinks + + .. versionadded:: 3.3 + + +.. function:: symlink(source, link_name, target_is_directory=False, *, dir_fd=None) + + Create a symbolic link pointing to *source* named *link_name*. + + On Windows, a symlink represents either a file or a directory, and does not + morph to the target dynamically. If the target is present, the type of the + symlink will be created to match. Otherwise, the symlink will be created + as a directory if *target_is_directory* is ``True`` or a file symlink (the + default) otherwise. On non-Window platforms, *target_is_directory* is ignored. Symbolic link support was introduced in Windows 6.0 (Vista). :func:`symlink` will raise a :exc:`NotImplementedError` on Windows versions earlier than 6.0. + This function can support :ref:`paths relative to directory descriptors + <dir_fd>`. + .. note:: - The *SeCreateSymbolicLinkPrivilege* is required in order to successfully - create symlinks. This privilege is not typically granted to regular - users but is available to accounts which can escalate privileges to the - administrator level. Either obtaining the privilege or running your + On Windows, the *SeCreateSymbolicLinkPrivilege* is required in order to + successfully create symlinks. This privilege is not typically granted to + regular users but is available to accounts which can escalate privileges + to the administrator level. Either obtaining the privilege or running your application as an administrator are ways to successfully create symlinks. + :exc:`OSError` is raised when the function is called by an unprivileged user. @@ -1467,31 +2059,83 @@ Files and Directories .. versionchanged:: 3.2 Added support for Windows 6.0 (Vista) symbolic links. + .. versionadded:: 3.3 + Added the *dir_fd* argument, and now allow *target_is_directory* + on non-Windows platforms. + + +.. function:: sync() + + Force write of everything to disk. + + Availability: Unix. + + .. versionadded:: 3.3 + -.. function:: unlink(path) +.. function:: truncate(path, length) - Remove (delete) the file *path*. This is the same function as - :func:`remove`; the :func:`unlink` name is its traditional Unix - name. + Truncate the file corresponding to *path*, so that it is at most + *length* bytes in size. + + This function can support :ref:`specifying a file descriptor <path_fd>`. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. function:: unlink(path, *, dir_fd=None) + + Remove (delete) the file *path*. This function is identical to + :func:`remove`; the ``unlink`` name is its traditional Unix + name. Please see the documentation for :func:`remove` for + further information. Availability: Unix, Windows. + .. versionadded:: 3.3 + The *dir_fd* parameter. + + +.. function:: utime(path, times=None, *, ns=None, dir_fd=None, follow_symlinks=True) -.. function:: utime(path, times) + Set the access and modified times of the file specified by *path*. - Set the access and modified times of the file specified by *path*. If *times* - is ``None``, then the file's access and modified times are set to the current - time. (The effect is similar to running the Unix program :program:`touch` on - the path.) Otherwise, *times* must be a 2-tuple of numbers, of the form - ``(atime, mtime)`` which is used to set the access and modified times, - respectively. Whether a directory can be given for *path* depends on whether - the operating system implements directories as files (for example, Windows - does not). Note that the exact times you set here may not be returned by a - subsequent :func:`~os.stat` call, depending on the resolution with which your - operating system records access and modification times; see :func:`~os.stat`. + :func:`utime` takes two optional parameters, *times* and *ns*. + These specify the times set on *path* and are used as follows: + + - If *ns* is not ``None``, + it must be a 2-tuple of the form ``(atime_ns, mtime_ns)`` + where each member is an int expressing nanoseconds. + - If *times* is not ``None``, + it must be a 2-tuple of the form ``(atime, mtime)`` + where each member is an int or float expressing seconds. + - If *times* and *ns* are both ``None``, + this is equivalent to specifying ``ns=(atime_ns, mtime_ns)`` + where both times are the current time. + + It is an error to specify tuples for both *times* and *ns*. + + Whether a directory can be given for *path* + depends on whether the operating system implements directories as files + (for example, Windows does not). Note that the exact times you set here may + not be returned by a subsequent :func:`~os.stat` call, depending on the + resolution with which your operating system records access and modification + times; see :func:`~os.stat`. The best way to preserve exact times is to + use the *st_atime_ns* and *st_mtime_ns* fields from the :func:`os.stat` + result object with the *ns* parameter to `utime`. + + This function can support :ref:`specifying a file descriptor <path_fd>`, + :ref:`paths relative to directory descriptors <dir_fd>` and :ref:`not + following symlinks <follow_symlinks>`. Availability: Unix, Windows. + .. versionadded:: 3.3 + Added support for specifying an open file descriptor for *path*, + and the *dir_fd*, *follow_symlinks*, and *ns* parameters. + .. function:: walk(top, topdown=True, onerror=None, followlinks=False) @@ -1538,9 +2182,9 @@ Files and Directories .. note:: - Be aware that setting *followlinks* to ``True`` can lead to infinite recursion if a - link points to a parent directory of itself. :func:`walk` does not keep track of - the directories it visited already. + Be aware that setting *followlinks* to ``True`` can lead to infinite + recursion if a link points to a parent directory of itself. :func:`walk` + does not keep track of the directories it visited already. .. note:: @@ -1576,6 +2220,137 @@ Files and Directories os.rmdir(os.path.join(root, name)) +.. function:: fwalk(top='.', topdown=True, onerror=None, *, follow_symlinks=False, dir_fd=None) + + .. index:: + single: directory; walking + single: directory; traversal + + This behaves exactly like :func:`walk`, except that it yields a 4-tuple + ``(dirpath, dirnames, filenames, dirfd)``, and it supports ``dir_fd``. + + *dirpath*, *dirnames* and *filenames* are identical to :func:`walk` output, + and *dirfd* is a file descriptor referring to the directory *dirpath*. + + This function always supports :ref:`paths relative to directory descriptors + <dir_fd>` and :ref:`not following symlinks <follow_symlinks>`. Note however + that, unlike other functions, the :func:`fwalk` default value for + *follow_symlinks* is ``False``. + + .. note:: + + Since :func:`fwalk` yields file descriptors, those are only valid until + the next iteration step, so you should duplicate them (e.g. with + :func:`dup`) if you want to keep them longer. + + This example displays the number of bytes taken by non-directory files in each + directory under the starting directory, except that it doesn't look under any + CVS subdirectory:: + + import os + for root, dirs, files, rootfd in os.fwalk('python/Lib/email'): + print(root, "consumes", end="") + print(sum([os.stat(name, dir_fd=rootfd).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 + + In the next example, walking the tree bottom-up is essential: + :func:`rmdir` doesn't allow deleting a directory before the directory is + empty:: + + # Delete everything reachable from the directory named in "top", + # assuming there are no symbolic links. + # CAUTION: This is dangerous! For example, if top == '/', it + # could delete all your disk files. + import os + for root, dirs, files, rootfd in os.fwalk(top, topdown=False): + for name in files: + os.unlink(name, dir_fd=rootfd) + for name in dirs: + os.rmdir(name, dir_fd=rootfd) + + Availability: Unix. + + .. versionadded:: 3.3 + + +Linux extended attributes +~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. versionadded:: 3.3 + +These functions are all available on Linux only. + +.. function:: getxattr(path, attribute, *, follow_symlinks=True) + + Return the value of the extended filesystem attribute *attribute* for + *path*. *attribute* can be bytes or str. If it is str, it is encoded + with the filesystem encoding. + + This function can support :ref:`specifying a file descriptor <path_fd>` and + :ref:`not following symlinks <follow_symlinks>`. + + +.. function:: listxattr(path=None, *, follow_symlinks=True) + + Return a list of the extended filesystem attributes on *path*. The + attributes in the list are represented as strings decoded with the filesystem + encoding. If *path* is ``None``, :func:`listxattr` will examine the current + directory. + + This function can support :ref:`specifying a file descriptor <path_fd>` and + :ref:`not following symlinks <follow_symlinks>`. + + +.. function:: removexattr(path, attribute, *, follow_symlinks=True) + + Removes the extended filesystem attribute *attribute* from *path*. + *attribute* should be bytes or str. If it is a string, it is encoded + with the filesystem encoding. + + This function can support :ref:`specifying a file descriptor <path_fd>` and + :ref:`not following symlinks <follow_symlinks>`. + + +.. function:: setxattr(path, attribute, value, flags=0, *, follow_symlinks=True) + + Set the extended filesystem attribute *attribute* on *path* to *value*. + *attribute* must be a bytes or str with no embedded NULs. If it is a str, + it is encoded with the filesystem encoding. *flags* may be + :data:`XATTR_REPLACE` or :data:`XATTR_CREATE`. If :data:`XATTR_REPLACE` is + given and the attribute does not exist, ``EEXISTS`` will be raised. + If :data:`XATTR_CREATE` is given and the attribute already exists, the + attribute will not be created and ``ENODATA`` will be raised. + + This function can support :ref:`specifying a file descriptor <path_fd>` and + :ref:`not following symlinks <follow_symlinks>`. + + .. note:: + + A bug in Linux kernel versions less than 2.6.39 caused the flags argument + to be ignored on some filesystems. + + +.. data:: XATTR_SIZE_MAX + + The maximum size the value of an extended attribute can be. Currently, this + is 64 KiB on Linux. + + +.. data:: XATTR_CREATE + + This is a possible value for the flags argument in :func:`setxattr`. It + indicates the operation must create an attribute. + + +.. data:: XATTR_REPLACE + + This is a possible value for the flags argument in :func:`setxattr`. It + indicates the operation must replace an existing attribute. + + .. _os-process: Process Management @@ -1583,7 +2358,7 @@ Process Management These functions may be used to create and manage processes. -The various :func:`exec\*` functions take a list of arguments for the new +The various :func:`exec\* <execl>` functions take a list of arguments for the new program loaded into the process. In each case, the first of these arguments is passed to the new program as its own name rather than as an argument a user may have typed on a command line. For the C programmer, this is the ``argv[0]`` @@ -1621,9 +2396,9 @@ to be ignored. descriptors are not flushed, so if there may be data buffered on these open files, you should flush them using :func:`sys.stdout.flush` or :func:`os.fsync` before calling an - :func:`exec\*` function. + :func:`exec\* <execl>` function. - The "l" and "v" variants of the :func:`exec\*` functions differ in how + The "l" and "v" variants of the :func:`exec\* <execl>` functions differ in how command-line arguments are passed. The "l" variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written; the individual parameters simply become additional parameters to the :func:`execl\*` @@ -1635,7 +2410,7 @@ to be ignored. The variants which include a "p" near the end (:func:`execlp`, :func:`execlpe`, :func:`execvp`, and :func:`execvpe`) will use the :envvar:`PATH` environment variable to locate the program *file*. When the - environment is being replaced (using one of the :func:`exec\*e` variants, + environment is being replaced (using one of the :func:`exec\*e <execl>` variants, discussed in the next paragraph), the new environment is used as the source of the :envvar:`PATH` variable. The other variants, :func:`execl`, :func:`execle`, :func:`execv`, and :func:`execve`, will not use the :envvar:`PATH` variable to @@ -1649,8 +2424,16 @@ to be ignored. :func:`execlp`, :func:`execv`, and :func:`execvp` all cause the new process to inherit the environment of the current process. + For :func:`execve` on some platforms, *path* may also be specified as an open + file descriptor. This functionality may not be supported on your platform; + you can check whether or not it is available using :data:`os.supports_fd`. + If it is unavailable, using it will raise a :exc:`NotImplementedError`. + Availability: Unix, Windows. + .. versionadded:: 3.3 + Added support for specifying an open file descriptor for *path* + for :func:`execve`. .. function:: _exit(n) @@ -1844,6 +2627,8 @@ written in Python, such as a mail server's external command delivery program. will be set to *sig*. The Windows version of :func:`kill` additionally takes process handles to be killed. + See also :func:`signal.pthread_kill`. + .. versionadded:: 3.2 Windows support. @@ -1875,7 +2660,6 @@ written in Python, such as a mail server's external command delivery program. .. function:: popen(...) - :noindex: Run child processes, returning opened pipes for communications. These functions are described in section :ref:`os-newstreams`. @@ -1903,7 +2687,7 @@ written in Python, such as a mail server's external command delivery program. process. On Windows, the process id will actually be the process handle, so can be used with the :func:`waitpid` function. - The "l" and "v" variants of the :func:`spawn\*` functions differ in how + The "l" and "v" variants of the :func:`spawn\* <spawnl>` functions differ in how command-line arguments are passed. The "l" variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written; the individual parameters simply become additional parameters to the @@ -1915,7 +2699,7 @@ written in Python, such as a mail server's external command delivery program. The variants which include a second "p" near the end (:func:`spawnlp`, :func:`spawnlpe`, :func:`spawnvp`, and :func:`spawnvpe`) will use the :envvar:`PATH` environment variable to locate the program *file*. When the - environment is being replaced (using one of the :func:`spawn\*e` variants, + environment is being replaced (using one of the :func:`spawn\*e <spawnl>` variants, discussed in the next paragraph), the new environment is used as the source of the :envvar:`PATH` variable. The other variants, :func:`spawnl`, :func:`spawnle`, :func:`spawnv`, and :func:`spawnve`, will not use the @@ -1949,7 +2733,7 @@ written in Python, such as a mail server's external command delivery program. .. data:: P_NOWAIT P_NOWAITO - Possible values for the *mode* parameter to the :func:`spawn\*` family of + Possible values for the *mode* parameter to the :func:`spawn\* <spawnl>` family of functions. If either of these values is given, the :func:`spawn\*` functions will return as soon as the new process has been created, with the process id as the return value. @@ -1959,7 +2743,7 @@ written in Python, such as a mail server's external command delivery program. .. data:: P_WAIT - Possible value for the *mode* parameter to the :func:`spawn\*` family of + Possible value for the *mode* parameter to the :func:`spawn\* <spawnl>` family of functions. If this is given as *mode*, the :func:`spawn\*` functions will not return until the new process has run to completion and will return the exit code of the process the run is successful, or ``-signal`` if a signal kills the @@ -1971,11 +2755,11 @@ written in Python, such as a mail server's external command delivery program. .. data:: P_DETACH P_OVERLAY - Possible values for the *mode* parameter to the :func:`spawn\*` family of + Possible values for the *mode* parameter to the :func:`spawn\* <spawnl>` family of functions. These are less portable than those listed above. :const:`P_DETACH` is similar to :const:`P_NOWAIT`, but the new process is detached from the console of the calling process. If :const:`P_OVERLAY` is used, the current - process will be replaced; the :func:`spawn\*` function will not return. + process will be replaced; the :func:`spawn\* <spawnl>` function will not return. Availability: Windows. @@ -2034,14 +2818,30 @@ written in Python, such as a mail server's external command delivery program. .. function:: times() - Return a 5-tuple of floating point numbers indicating accumulated (processor - or other) times, in seconds. The items are: user time, system time, - children's user time, children's system time, and elapsed real time since a - fixed point in the past, in that order. See the Unix manual page + Returns the current global process times. + The return value is an object with five attributes: + + * :attr:`user` - user time + * :attr:`system` - system time + * :attr:`children_user` - user time of all child processes + * :attr:`children_system` - system time of all child processes + * :attr:`elapsed` - elapsed real time since a fixed point in the past + + For backwards compatibility, this object also behaves like a five-tuple + containing :attr:`user`, :attr:`system`, :attr:`children_user`, + :attr:`children_system`, and :attr:`elapsed` in that order. + + See the Unix manual page :manpage:`times(2)` or the corresponding Windows Platform API documentation. - On Windows, only the first two items are filled, the others are zero. + On Windows, only :attr:`user` and :attr:`system` are known; the other + attributes are zero. + On OS/2, only :attr:`elapsed` is known; the other attributes are zero. - Availability: Unix, Windows + Availability: Unix, Windows. + + .. versionchanged:: 3.3 + Return type changed from a tuple to a tuple-like object + with named attributes. .. function:: wait() @@ -2054,6 +2854,58 @@ written in Python, such as a mail server's external command delivery program. Availability: Unix. +.. function:: waitid(idtype, id, options) + + Wait for the completion of one or more child processes. + *idtype* can be :data:`P_PID`, :data:`P_PGID` or :data:`P_ALL`. + *id* specifies the pid to wait on. + *options* is constructed from the ORing of one or more of :data:`WEXITED`, + :data:`WSTOPPED` or :data:`WCONTINUED` and additionally may be ORed with + :data:`WNOHANG` or :data:`WNOWAIT`. The return value is an object + representing the data contained in the :c:type:`siginfo_t` structure, namely: + :attr:`si_pid`, :attr:`si_uid`, :attr:`si_signo`, :attr:`si_status`, + :attr:`si_code` or ``None`` if :data:`WNOHANG` is specified and there are no + children in a waitable state. + + Availability: Unix. + + .. versionadded:: 3.3 + +.. data:: P_PID + P_PGID + P_ALL + + These are the possible values for *idtype* in :func:`waitid`. They affect + how *id* is interpreted. + + Availability: Unix. + + .. versionadded:: 3.3 + +.. data:: WEXITED + WSTOPPED + WNOWAIT + + Flags that can be used in *options* in :func:`waitid` that specify what + child signal to wait for. + + Availability: Unix. + + .. versionadded:: 3.3 + + +.. data:: CLD_EXITED + CLD_DUMPED + CLD_TRAPPED + CLD_CONTINUED + + These are the possible values for :attr:`si_code` in the result returned by + :func:`waitid`. + + Availability: Unix. + + .. versionadded:: 3.3 + .. function:: waitpid(pid, options) @@ -2079,8 +2931,8 @@ written in Python, such as a mail server's external command delivery program. (shifting makes cross-platform use of the function easier). A *pid* less than or equal to ``0`` has no special meaning on Windows, and raises an exception. The value of integer *options* has no effect. *pid* can refer to any process whose - id is known, not necessarily a child process. The :func:`spawn` functions called - with :const:`P_NOWAIT` return suitable process handles. + id is known, not necessarily a child process. The :func:`spawn\* <spawnl>` + functions called with :const:`P_NOWAIT` return suitable process handles. .. function:: wait3(options) @@ -2088,8 +2940,9 @@ written in Python, such as a mail server's external command delivery program. Similar to :func:`waitpid`, except no process id argument is given and a 3-element tuple containing the child's process id, exit status indication, and resource usage information is returned. Refer to :mod:`resource`.\ - :func:`getrusage` for details on resource usage information. The option - argument is the same as that provided to :func:`waitpid` and :func:`wait4`. + :func:`~resource.getrusage` for details on resource usage information. The + option argument is the same as that provided to :func:`waitpid` and + :func:`wait4`. Availability: Unix. @@ -2098,9 +2951,9 @@ written in Python, such as a mail server's external command delivery program. Similar to :func:`waitpid`, except a 3-element tuple, containing the child's process id, exit status indication, and resource usage information is returned. - Refer to :mod:`resource`.\ :func:`getrusage` for details on resource usage - information. The arguments to :func:`wait4` are the same as those provided to - :func:`waitpid`. + Refer to :mod:`resource`.\ :func:`~resource.getrusage` for details on + resource usage information. The arguments to :func:`wait4` are the same + as those provided to :func:`waitpid`. Availability: Unix. @@ -2118,7 +2971,7 @@ written in Python, such as a mail server's external command delivery program. This option causes child processes to be reported if they have been continued from a job control stop since their status was last reported. - Availability: Some Unix systems. + Availability: some Unix systems. .. data:: WUNTRACED @@ -2195,6 +3048,129 @@ used to determine the disposition of a process. Availability: Unix. +Interface to the scheduler +-------------------------- + +These functions control how a process is allocated CPU time by the operating +system. They are only available on some Unix platforms. For more detailed +information, consult your Unix manpages. + +.. versionadded:: 3.3 + +The following scheduling policies are exposed if they are a supported by the +operating system. + +.. data:: SCHED_OTHER + + The default scheduling policy. + +.. data:: SCHED_BATCH + + Scheduling policy for CPU-intensive processes that tries to preserve + interactivity on the rest of the computer. + +.. data:: SCHED_IDLE + + Scheduling policy for extremely low priority background tasks. + +.. data:: SCHED_SPORADIC + + Scheduling policy for sporadic server programs. + +.. data:: SCHED_FIFO + + A First In First Out scheduling policy. + +.. data:: SCHED_RR + + A round-robin scheduling policy. + +.. data:: SCHED_RESET_ON_FORK + + This flag can OR'ed with any other scheduling policy. When a process with + this flag set forks, its child's scheduling policy and priority are reset to + the default. + + +.. class:: sched_param(sched_priority) + + This class represents tunable scheduling parameters used in + :func:`sched_setparam`, :func:`sched_setscheduler`, and + :func:`sched_getparam`. It is immutable. + + At the moment, there is only one possible parameter: + + .. attribute:: sched_priority + + The scheduling priority for a scheduling policy. + + +.. function:: sched_get_priority_min(policy) + + Get the minimum priority value for *policy*. *policy* is one of the + scheduling policy constants above. + + +.. function:: sched_get_priority_max(policy) + + Get the maximum priority value for *policy*. *policy* is one of the + scheduling policy constants above. + + +.. function:: sched_setscheduler(pid, policy, param) + + Set the scheduling policy for the process with PID *pid*. A *pid* of 0 means + the calling process. *policy* is one of the scheduling policy constants + above. *param* is a :class:`sched_param` instance. + + +.. function:: sched_getscheduler(pid) + + Return the scheduling policy for the process with PID *pid*. A *pid* of 0 + means the calling process. The result is one of the scheduling policy + constants above. + + +.. function:: sched_setparam(pid, param) + + Set a scheduling parameters for the process with PID *pid*. A *pid* of 0 means + the calling process. *param* is a :class:`sched_param` instance. + + +.. function:: sched_getparam(pid) + + Return the scheduling parameters as a :class:`sched_param` instance for the + process with PID *pid*. A *pid* of 0 means the calling process. + + +.. function:: sched_rr_get_interval(pid) + + Return the round-robin quantum in seconds for the process with PID *pid*. A + *pid* of 0 means the calling process. + + +.. function:: sched_yield() + + Voluntarily relinquish the CPU. + + +.. function:: sched_setaffinity(pid, mask) + + Restrict the process with PID *pid* (or the current process if zero) to a + set of CPUs. *mask* is an iterable of integers representing the set of + CPUs to which the process should be restricted. + + +.. function:: sched_getaffinity(pid) + + Return the set of CPUs the process with PID *pid* (or the current process + if zero) is restricted to. + + .. seealso:: + :func:`multiprocessing.cpu_count` returns the number of CPUs in the + system. + + .. _os-path: Miscellaneous System Information @@ -2219,7 +3195,7 @@ Miscellaneous System Information included in ``confstr_names``, an :exc:`OSError` is raised with :const:`errno.EINVAL` for the error number. - Availability: Unix + Availability: Unix. .. data:: confstr_names @@ -2310,8 +3286,9 @@ Higher-level operations on pathnames are defined in the :mod:`os.path` module. .. data:: defpath - The default search path used by :func:`exec\*p\*` and :func:`spawn\*p\*` if the - environment doesn't have a ``'PATH'`` key. Also available via :mod:`os.path`. + The default search path used by :func:`exec\*p\* <execl>` and + :func:`spawn\*p\* <spawnl>` if the environment doesn't have a ``'PATH'`` + key. Also available via :mod:`os.path`. .. data:: linesep @@ -2341,6 +3318,10 @@ Miscellaneous Functions This function returns random bytes from an OS-specific randomness source. The returned data should be unpredictable enough for cryptographic applications, - though its exact quality depends on the OS implementation. On a UNIX-like - system this will query /dev/urandom, and on Windows it will use CryptGenRandom. - If a randomness source is not found, :exc:`NotImplementedError` will be raised. + though its exact quality depends on the OS implementation. On a Unix-like + system this will query ``/dev/urandom``, and on Windows it will use + ``CryptGenRandom()``. If a randomness source is not found, + :exc:`NotImplementedError` will be raised. + + For an easy-to-use interface to the random number generator + provided by your platform, please see :class:`random.SystemRandom`. |