uos
– 基础“操作系统”服务¶
警告
待实现。
|see_cpython_module| python:os
.
The uos
module contains functions for filesystem access and mounting,
terminal redirection and duplication, and the uname
and urandom
functions.
General functions¶
-
uos.
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 systemnodename
– the network name (can be the same assysname
)release
– the version of the underlying systemversion
– the MicroPython version and build datemachine
– an identifier for the underlying hardware (eg board, CPU)
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uos.
urandom
(n)¶ Return a bytes object with n random bytes. Whenever possible, it is generated by the hardware random number generator.
Filesystem access¶
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uos.
chdir
(path)¶ Change current directory.
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uos.
getcwd
()¶ Get the current directory.
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uos.
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.
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uos.
listdir
([dir])¶ With no argument, list the current directory. Otherwise list the given directory.
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uos.
mkdir
(path)¶ Create a new directory.
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uos.
remove
(path)¶ Remove a file.
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uos.
rmdir
(path)¶ Remove a directory.
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uos.
rename
(old_path, new_path)¶ Rename a file.
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uos.
stat
(path)¶ Get the status of a file or directory.
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uos.
statvfs
(path)¶ Get the status of a fileystem.
Returns a tuple with the filesystem information in the following order:
f_bsize
– file system block sizef_frsize
– fragment sizef_blocks
– size of fs in f_frsize unitsf_bfree
– number of free blocksf_bavail
– number of free blocks for unprivileged usersf_files
– number of inodesf_ffree
– number of free inodesf_favail
– number of free inodes for unprivileged usersf_flag
– mount flagsf_namemax
– maximum filename length
Parameters related to inodes:
f_files
,f_ffree
,f_avail
and thef_flags
parameter may return0
as they can be unavailable in a port-specific implementation.
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uos.
sync
()¶ Sync all filesystems.
Terminal redirection and duplication¶
-
uos.
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 thereadinto()
andwrite()
methods. The stream should be in non-blocking mode andreadinto()
should returnNone
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 mount()
and
umount()
functions, and possibly various filesystem implementations
represented by VFS classes.
-
uos.
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.
-
uos.
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.
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class
uos.
VfsFat
(block_dev)¶ 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
mount()
.-
static
mkfs
(block_dev)¶ Build a FAT filesystem on block_dev.
-
static
-
class
uos.
VfsLfs1
(block_dev, readsize=32, progsize=32, lookahead=32)¶ Create a filesystem object that uses the littlefs v1 filesystem format. Storage of the littlefs filesystem is provided by block_dev, which must support the extended interface. Objects created by this constructor can be mounted using
mount()
.See Working with filesystems for more information.
-
static
mkfs
(block_dev, readsize=32, progsize=32, lookahead=32)¶ Build a Lfs1 filesystem on block_dev.
注解
There are reports of littlefs v1 failing in certain situations, for details see littlefs issue 347.
-
static
-
class
uos.
VfsLfs2
(block_dev, readsize=32, progsize=32, lookahead=32, mtime=True)¶ Create a filesystem object that uses the littlefs v2 filesystem format. Storage of the littlefs filesystem is provided by block_dev, which must support the extended interface. Objects created by this constructor can be mounted using
mount()
.The mtime argument enables modification timestamps for files, stored using littlefs attributes. This option can be disabled or enabled differently each mount time and timestamps will only be added or updated if mtime is enabled, otherwise the timestamps will remain untouched. Littlefs v2 filesystems without timestamps will work without reformatting and timestamps will be added transparently to existing files once they are opened for writing. When mtime is enabled uos.stat on files without timestamps will return 0 for the timestamp.
See Working with filesystems for more information.
-
static
mkfs
(block_dev, readsize=32, progsize=32, lookahead=32)¶ Build a Lfs2 filesystem on block_dev.
注解
There are reports of littlefs v2 failing in certain situations, for details see littlefs issue 295.
-
static
Block devices¶
A block device is an object which implements the block protocol. This enables a
device to support MicroPython filesystems. The physical hardware is represented
by a user defined class. The AbstractBlockDev
class is a template for
the design of such a class: MicroPython does not actually provide that class,
but an actual block device class must implement the methods described below.
A concrete implementation of this class will usually allow access to the
memory-like functionality of a piece of hardware (like flash memory). A block
device can be formatted to any supported filesystem and mounted using uos
methods.
See Working with filesystems for example implementations of block devices using the two variants of the block protocol described below.
Simple and extended interface¶
There are two compatible signatures for the readblocks
and writeblocks
methods (see below), in order to support a variety of use cases. A given block
device may implement one form or the other, or both at the same time. The second
form (with the offset parameter) is referred to as the “extended interface”.
Some filesystems (such as littlefs) that require more control over write operations, for example writing to sub-block regions without erasing, may require that the block device supports the extended interface.
-
class
uos.
AbstractBlockDev
(...)¶ Construct a block device object. The parameters to the constructor are dependent on the specific block device.
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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.
-
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.
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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 littlefsioctl(6, ...)
must also be intercepted. The need for others is hardware dependent.Unless otherwise stated
ioctl(op, arg)
can returnNone
. Consequently an implementation can ignore unused values ofop
. Whereop
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 anOSError
errno code.
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