Struct OpenOptions

pub struct OpenOptions(/* private fields */);

Options and flags which can be used to configure how a file is opened.

This builder exposes the ability to configure how a File is opened and what operations are permitted on the open file. The File::open and File::create methods are aliases for commonly used options using this builder.

Generally speaking, when using OpenOptions, you’ll first call OpenOptions::new, then chain calls to methods to set each option, then call OpenOptions::open, passing the path of the file you’re trying to open. This will give you a std::io::Result with a File inside that you can further operate on.

Examples

Opening a file to read:

use compio_fs::OpenOptions;

let file = OpenOptions::new().read(true).open("foo.txt").await.unwrap();

Opening a file for both reading and writing, as well as creating it if it doesn’t exist:

use compio_fs::OpenOptions;

let file = OpenOptions::new()
    .read(true)
    .write(true)
    .create(true)
    .open("foo.txt")
    .await
    .unwrap();

Implementations

impl OpenOptions

pub fn new() -> Self

Creates a blank new set of options ready for configuration.

pub fn read(&mut self, read: bool) -> &mut Self

Sets the option for read access.

This option, when true, will indicate that the file should be read-able if opened.

pub fn write(&mut self, write: bool) -> &mut Self

Sets the option for write access.

This option, when true, will indicate that the file should be write-able if opened.

pub fn truncate(&mut self, truncate: bool) -> &mut Self

Sets the option for truncating a previous file.

If a file is successfully opened with this option set it will truncate the file to 0 length if it already exists.

The file must be opened with write access for truncate to work.

pub fn create(&mut self, create: bool) -> &mut Self

Sets the option to create a new file, or open it if it already exists.

In order for the file to be created, OpenOptions::write access must be used.

pub fn create_new(&mut self, create_new: bool) -> &mut Self

Sets the option to create a new file, failing if it already exists.

No file is allowed to exist at the target location, also no (dangling) symlink. In this way, if the call succeeds, the file returned is guaranteed to be new.

This option is useful because it is atomic. Otherwise between checking whether a file exists and creating a new one, the file may have been created by another process (a TOCTOU race condition / attack).

If .create_new(true) is set, .create() and .truncate() are ignored.

The file must be opened with write or append access in order to create a new file.

pub async fn open(&self, path: impl AsRef<Path>) -> Result<File>

Opens a file at path with the options specified by self.

impl OpenOptions

pub fn custom_flags(&mut self, flags: i32) -> &mut Self

Available on Unix only.

Pass custom flags to the flags argument of open.

The bits that define the access mode are masked out with O_ACCMODE, to ensure they do not interfere with the access mode set by Rusts options.

Custom flags can only set flags, not remove flags set by Rusts options. This options overwrites any previously set custom flags.

pub fn mode(&mut self, mode: u32) -> &mut Self

Available on Unix only.

Sets the mode bits that a new file will be created with.

If a new file is created as part of an OpenOptions::open call then this specified mode will be used as the permission bits for the new file. If no mode is set, the default of 0o666 will be used. The operating system masks out bits with the system’s umask, to produce the final permissions.

Trait Implementations

impl Clone for OpenOptions

fn clone(&self) -> OpenOptions

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for OpenOptions

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.