:mod:`uos` -- basic "operating system" services

.. module:: uos
 :synopsis: basic "operating system" services

|see_cpython_module| :mod:`python:os`.

The uos module contains functions for filesystem access and mounting, terminal redirection and duplication, and the uname and urandom functions.

General functions

.. function:: uname()

 Return a tuple (possibly a named tuple) containing information about the
 underlying machine and/or its operating system. The tuple has five fields
 in the following order, each of them being a string:

 * ``sysname`` -- the name of the underlying system
 * ``nodename`` -- the network name (can be the same as ``sysname``)
 * ``release`` -- the version of the underlying system
 * ``version`` -- the MicroPython version and build date
 * ``machine`` -- an identifier for the underlying hardware (eg board, CPU)

.. function:: urandom(n)

 Return a bytes object with *n* random bytes. Whenever possible, it is
 generated by the hardware random number generator.

Filesystem access

.. function:: chdir(path)

 Change current directory.

.. function:: getcwd()

 Get the current directory.

.. function:: ilistdir([dir])

 This function returns an iterator which then yields tuples corresponding to
 the entries in the directory that it is listing. With no argument it lists the
 current directory, otherwise it lists the directory given by *dir*.

 The tuples have the form *(name, type, inode[, size])*:

 - *name* is a string (or bytes if *dir* is a bytes object) and is the name of
 the entry;
 - *type* is an integer that specifies the type of the entry, with 0x4000 for
 directories and 0x8000 for regular files;
 - *inode* is an integer corresponding to the inode of the file, and may be 0
 for filesystems that don't have such a notion.
 - Some platforms may return a 4-tuple that includes the entry's *size*. For
 file entries, *size* is an integer representing the size of the file
 or -1 if unknown. Its meaning is currently undefined for directory
 entries.

.. function:: listdir([dir])

 With no argument, list the current directory. Otherwise list the given directory.

.. function:: mkdir(path)

 Create a new directory.

.. function:: remove(path)

 Remove a file.

.. function:: rmdir(path)

 Remove a directory.

.. function:: rename(old_path, new_path)

 Rename a file.

.. function:: stat(path)

 Get the status of a file or directory.

.. function:: statvfs(path)

 Get the status of a fileystem.

 Returns a tuple with the filesystem information in the following order:

 * ``f_bsize`` -- file system block size
 * ``f_frsize`` -- fragment size
 * ``f_blocks`` -- size of fs in f_frsize units
 * ``f_bfree`` -- number of free blocks
 * ``f_bavail`` -- number of free blocks for unprivileged users
 * ``f_files`` -- number of inodes
 * ``f_ffree`` -- number of free inodes
 * ``f_favail`` -- number of free inodes for unprivileged users
 * ``f_flag`` -- mount flags
 * ``f_namemax`` -- maximum filename length

 Parameters related to inodes: ``f_files``, ``f_ffree``, ``f_avail``
 and the ``f_flags`` parameter may return ``0`` as they can be unavailable
 in a port-specific implementation.

.. function:: sync()

 Sync all filesystems.

Terminal redirection and duplication

.. function:: dupterm(stream_object, index=0, /)

 Duplicate or switch the MicroPython terminal (the REPL) on the given `stream`-like
 object. The *stream_object* argument must be a native stream object, or derive
 from ``uio.IOBase`` and implement the ``readinto()`` and
 ``write()`` methods. The stream should be in non-blocking mode and
 ``readinto()`` should return ``None`` if there is no data available for reading.

 After calling this function all terminal output is repeated on this stream,
 and any input that is available on the stream is passed on to the terminal input.

 The *index* parameter should be a non-negative integer and specifies which
 duplication slot is set. A given port may implement more than one slot (slot 0
 will always be available) and in that case terminal input and output is
 duplicated on all the slots that are set.

 If ``None`` is passed as the *stream_object* then duplication is cancelled on
 the slot given by *index*.

 The function returns the previous stream-like object in the given slot.

Filesystem mounting

Some ports provide a Virtual Filesystem (VFS) and the ability to mount multiple "real" filesystems within this VFS. Filesystem objects can be mounted at either the root of the VFS, or at a subdirectory that lives in the root. This allows dynamic and flexible configuration of the filesystem that is seen by Python programs. Ports that have this functionality provide the :func:`mount` and :func:`umount` functions, and possibly various filesystem implementations represented by VFS classes.

.. function:: mount(fsobj, mount_point, *, readonly)

 Mount the filesystem object *fsobj* at the location in the VFS given by the
 *mount_point* string. *fsobj* can be a a VFS object that has a ``mount()``
 method, or a block device. If it's a block device then the filesystem type
 is automatically detected (an exception is raised if no filesystem was
 recognised). *mount_point* may be ``'/'`` to mount *fsobj* at the root,
 or ``'/<name>'`` to mount it at a subdirectory under the root.

 If *readonly* is ``True`` then the filesystem is mounted read-only.

 During the mount process the method ``mount()`` is called on the filesystem
 object.

 Will raise ``OSError(EPERM)`` if *mount_point* is already mounted.

.. function:: umount(mount_point)

 Unmount a filesystem. *mount_point* can be a string naming the mount location,
 or a previously-mounted filesystem object. During the unmount process the
 method ``umount()`` is called on the filesystem object.

 Will raise ``OSError(EINVAL)`` if *mount_point* is not found.

Create a filesystem object that uses the FAT filesystem format. Storage of the FAT filesystem is provided by block_dev. Objects created by this constructor can be mounted using :func:`mount`.

.. staticmethod:: mkfs(block_dev)

 Build a FAT filesystem on *block_dev*.

Create a filesystem object that uses the :ref:`extended interface <block-device-interface>`. Objects created by this constructor can be mounted using :func:`mount`.

See :ref:`filesystem` for more information.

.. staticmethod:: mkfs(block_dev, readsize=32, progsize=32, lookahead=32)

 Build a Lfs1 filesystem on *block_dev*.

.. staticmethod:: mkfs(block_dev, readsize=32, progsize=32, lookahead=32)

 Build a Lfs2 filesystem on *block_dev*.

.. method:: readblocks(block_num, buf)
 readblocks(block_num, buf, offset)

 The first form reads aligned, multiples of blocks.
 Starting at the block given by the index *block_num*, read blocks from
 the device into *buf* (an array of bytes).
 The number of blocks to read is given by the length of *buf*,
 which will be a multiple of the block size.

 The second form allows reading at arbitrary locations within a block,
 and arbitrary lengths.
 Starting at block index *block_num*, and byte offset within that block
 of *offset*, read bytes from the device into *buf* (an array of bytes).
 The number of bytes to read is given by the length of *buf*.

.. method:: writeblocks(block_num, buf)
 writeblocks(block_num, buf, offset)

 The first form writes aligned, multiples of blocks, and requires that the
 blocks that are written to be first erased (if necessary) by this method.
 Starting at the block given by the index *block_num*, write blocks from
 *buf* (an array of bytes) to the device.
 The number of blocks to write is given by the length of *buf*,
 which will be a multiple of the block size.

 The second form allows writing at arbitrary locations within a block,
 and arbitrary lengths. Only the bytes being written should be changed,
 and the caller of this method must ensure that the relevant blocks are
 erased via a prior ``ioctl`` call.
 Starting at block index *block_num*, and byte offset within that block
 of *offset*, write bytes from *buf* (an array of bytes) to the device.
 The number of bytes to write is given by the length of *buf*.

 Note that implementations must never implicitly erase blocks if the offset
 argument is specified, even if it is zero.

.. method:: ioctl(op, arg)

 Control the block device and query its parameters. The operation to
 perform is given by *op* which is one of the following integers:

 - 1 -- initialise the device (*arg* is unused)
 - 2 -- shutdown the device (*arg* is unused)
 - 3 -- sync the device (*arg* is unused)
 - 4 -- get a count of the number of blocks, should return an integer
 (*arg* is unused)
 - 5 -- get the number of bytes in a block, should return an integer,
 or ``None`` in which case the default value of 512 is used
 (*arg* is unused)
 - 6 -- erase a block, *arg* is the block number to erase

 As a minimum ``ioctl(4, ...)`` must be intercepted; for littlefs
 ``ioctl(6, ...)`` must also be intercepted. The need for others is
 hardware dependent.

 Unless otherwise stated ``ioctl(op, arg)`` can return ``None``.
 Consequently an implementation can ignore unused values of ``op``. Where
 ``op`` is intercepted, the return value for operations 4 and 5 are as
 detailed above. Other operations should return 0 on success and non-zero
 for failure, with the value returned being an ``OSError`` errno code.

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