[−][src]Struct async_fs::File
An open file on the filesystem.
Depending on what options the file was opened with, this type can be used for reading and/or writing.
Files are automatically closed when they get dropped and any errors detected on closing are
ignored. Use the sync_all()
method before dropping a file if such
errors need to be handled.
NOTE: If writing to a file, make sure to call
flush()
, sync_data()
,
or sync_all()
before dropping the file or else some written data
might get lost!
Examples
Create a new file and write some bytes to it:
use async_fs::File; use futures_lite::io::AsyncWriteExt; let mut file = File::create("a.txt").await?; file.write_all(b"Hello, world!").await?; file.flush().await?;
Read the contents of a file into a vector of bytes:
use async_fs::File; use futures_lite::io::AsyncReadExt; let mut file = File::open("a.txt").await?; let mut contents = Vec::new(); file.read_to_end(&mut contents).await?;
Implementations
impl File
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pub async fn open<P: AsRef<Path>>(path: P) -> Result<File>
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Opens a file in read-only mode.
See the OpenOptions::open()
function for more options.
Errors
An error will be returned in the following situations:
path
does not point to an existing file.- The current process lacks permissions to read the file.
- Some other I/O error occurred.
For more details, see the list of errors documented by OpenOptions::open()
.
Examples
use async_fs::File; let file = File::open("a.txt").await?;
pub async fn create<P: AsRef<Path>>(path: P) -> Result<File>
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Opens a file in write-only mode.
This method will create a file if it does not exist, and will truncate it if it does.
See the OpenOptions::open
function for more options.
Errors
An error will be returned in the following situations:
- The file's parent directory does not exist.
- The current process lacks permissions to write to the file.
- Some other I/O error occurred.
For more details, see the list of errors documented by OpenOptions::open()
.
Examples
use async_fs::File; let file = File::create("a.txt").await?;
pub async fn sync_all<'_>(&'_ mut self) -> Result<()>
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Synchronizes OS-internal buffered contents and metadata to disk.
This function will ensure that all in-memory data reaches the filesystem.
This can be used to handle errors that would otherwise only be caught by closing the file. When a file is dropped, errors in synchronizing this in-memory data are ignored.
Examples
use async_fs::File; use futures_lite::io::AsyncWriteExt; let mut file = File::create("a.txt").await?; file.write_all(b"Hello, world!").await?; file.sync_all().await?;
pub async fn sync_data<'_>(&'_ mut self) -> Result<()>
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Synchronizes OS-internal buffered contents to disk.
This is similar to sync_all()
, except that file metadata may not
be synchronized.
This is intended for use cases that must synchronize the contents of the file, but don't need the file metadata synchronized to disk.
Note that some platforms may simply implement this in terms of
sync_all()
.
Examples
use async_fs::File; use futures_lite::io::AsyncWriteExt; let mut file = File::create("a.txt").await?; file.write_all(b"Hello, world!").await?; file.sync_data().await?;
pub async fn set_len<'_>(&'_ mut self, size: u64) -> Result<()>
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Truncates or extends the file.
If size
is less than the current file size, then the file will be truncated. If it is
greater than the current file size, then the file will be extended to size
and have all
intermediate data filled with zeros.
The file's cursor stays at the same position, even if the cursor ends up being past the end of the file after this operation.
Examples
use async_fs::File; let mut file = File::create("a.txt").await?; file.set_len(10).await?;
pub async fn metadata<'_>(&'_ self) -> Result<Metadata>
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Reads the file's metadata.
Examples
use async_fs::File; let file = File::open("a.txt").await?; let metadata = file.metadata().await?;
pub async fn set_permissions<'_>(&'_ self, perm: Permissions) -> Result<()>
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Changes the permissions on the file.
Errors
An error will be returned in the following situations:
- The current process lacks permissions to change attributes on the file.
- Some other I/O error occurred.
Examples
use async_fs::File; let file = File::create("a.txt").await?; let mut perms = file.metadata().await?.permissions(); perms.set_readonly(true); file.set_permissions(perms).await?;
Trait Implementations
impl AsRawFd for File
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impl AsyncRead for File
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fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8]
) -> Poll<Result<usize>>
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self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8]
) -> Poll<Result<usize>>
fn poll_read_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>]
) -> Poll<Result<usize, Error>>
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self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>]
) -> Poll<Result<usize, Error>>
impl AsyncSeek for File
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impl AsyncWrite for File
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fn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8]
) -> Poll<Result<usize>>
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self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8]
) -> Poll<Result<usize>>
fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>
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fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>
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fn poll_write_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>
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self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>
impl Debug for File
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impl From<File> for File
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Auto Trait Implementations
impl !RefUnwindSafe for File
impl Send for File
impl Sync for File
impl Unpin for File
impl !UnwindSafe for File
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<R> AsyncReadExt for R where
R: AsyncRead + ?Sized,
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R: AsyncRead + ?Sized,
fn read(&'a mut self, buf: &'a mut [u8]) -> ReadFuture<'a, Self> where
Self: Unpin,
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Self: Unpin,
fn read_vectored(
&'a mut self,
bufs: &'a mut [IoSliceMut<'a>]
) -> ReadVectoredFuture<'a, Self> where
Self: Unpin,
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&'a mut self,
bufs: &'a mut [IoSliceMut<'a>]
) -> ReadVectoredFuture<'a, Self> where
Self: Unpin,
fn read_to_end(&'a mut self, buf: &'a mut Vec<u8>) -> ReadToEndFuture<'a, Self> where
Self: Unpin,
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Self: Unpin,
fn read_to_string(
&'a mut self,
buf: &'a mut String
) -> ReadToStringFuture<'a, Self> where
Self: Unpin,
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&'a mut self,
buf: &'a mut String
) -> ReadToStringFuture<'a, Self> where
Self: Unpin,
fn read_exact(&'a mut self, buf: &'a mut [u8]) -> ReadExactFuture<'a, Self> where
Self: Unpin,
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Self: Unpin,
fn take(self, limit: u64) -> Take<Self>
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fn bytes(self) -> Bytes<Self>
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fn chain<R>(self, next: R) -> Chain<Self, R> where
R: AsyncRead,
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R: AsyncRead,
impl<S> AsyncSeekExt for S where
S: AsyncSeek + ?Sized,
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S: AsyncSeek + ?Sized,
fn seek(&mut self, pos: SeekFrom) -> SeekFuture<'_, Self> where
Self: Unpin,
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Self: Unpin,
impl<W> AsyncWriteExt for W where
W: AsyncWrite + ?Sized,
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W: AsyncWrite + ?Sized,
fn write(&'a mut self, buf: &'a [u8]) -> WriteFuture<'a, Self> where
Self: Unpin,
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Self: Unpin,
fn write_vectored(
&'a mut self,
bufs: &'a [IoSlice<'a>]
) -> WriteVectoredFuture<'a, Self> where
Self: Unpin,
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&'a mut self,
bufs: &'a [IoSlice<'a>]
) -> WriteVectoredFuture<'a, Self> where
Self: Unpin,
fn write_all(&'a mut self, buf: &'a [u8]) -> WriteAllFuture<'a, Self> where
Self: Unpin,
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Self: Unpin,
fn flush(&mut self) -> FlushFuture<'_, Self> where
Self: Unpin,
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Self: Unpin,
fn close(&mut self) -> CloseFuture<'_, Self> where
Self: Unpin,
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Self: Unpin,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,