---
title: "uos"
aliases:
    - firmwareapi/micropython/uos.html
    - firmwareapi/micropython/uos.md
    - chapter/firmwareapi/micropython/uos
---

The `uos` module contains functions for filesystem access and `urandom` function.

## Port Specifics

The filesystem has `/` as the root directory and the available physical drives are accessible from here. They are currently:

* `/flash` – the internal flash filesystem
* `/sd` – the SD card (if it exists)

## Methods

#### uos.uname()

Return information about the system, firmware release version, and MicroPython interpreter version.

#### uos.chdir(path)

Change current directory.

#### uos.getcwd()

Get the current directory.

#### uos.listdir(\[dir\])

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

#### uos.mkdir(path)

Create a new directory.

#### uos.remove(path)

Remove a file.

#### uos.rmdir(path)

Remove a directory.

#### uos.rename(old\_path, new\_path)

Rename a file.

#### uos.stat(path)

Get the status of a file or directory.

The return value is a tuple with the following 10 values, in order:

* `st_mode`: protection bits.
* `st_ino`: `inode` number. (not implemented, returns 0)
* `st_dev`: device. (not implemented, returns 0)
* `st_nlink`: number of hard links. (not implemented, returns 0)
* `st_uid`: user id of owner. (not implemented, returns 0)
* `st_gid`: group id of owner. (not implemented, returns 0)
* `st_size`: size of file in bytes.
* `st_atime`: time of most recent access.
* `st_mtime`: time of most recent content modification.
* `st_ctime`: time of most recent metadata change.

#### uos.getfree(path)

Returns the free space (in KiB) in the drive specified by path.

#### uos.sync()

Sync all filesystems.

#### uos.urandom(n)

Return a bytes object with n random bytes.

#### uos.unlink(path)

Alias for the `remove()` method.

#### uos.mount(block\_device, mount\_point, \* , readonly=False)

Mounts a block device (like an SD object) in the specified mount point. Example:

```python
uos.mount(sd, '/sd')
```

#### uos.umount(mount\_point)

Unmounts a previously mounted block device from the specified mount point. Example:

```python
uos.umount('/sd')
```

#### uos.mkfs(block\_device or path)

Formats the specified path, must be either `/flash` or `/sd`. A block device can also be passed like an SD object before being mounted.

#### uos.dupterm(stream\_object)

Duplicate the terminal (the REPL) on the passed stream-like object. The given object must at least implement the `read()` and `write()` methods.

## Constants

* `uos.sep`: Separation character used in paths