# Struct std::fs::File [−] [src]

    pub struct File {
        // some fields omitted
    }

A reference to an open file on the filesystem.

An instance of a `File` can be read and/or written depending on what options it was opened with. Files also implement `Seek` to alter the logical cursor that the file contains internally.

# Examples

fn main() { use std::io::prelude::*; use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::create("foo.txt")); try!(f.write_all(b"Hello, world!")); let mut f = try!(File::open("foo.txt")); let mut s = String::new(); try!(f.read_to_string(&mut s)); assert_eq!(s, "Hello, world!"); Ok(()) } }

    use std::io::prelude::*;
    use std::fs::File;

    let mut f = try!(File::create("foo.txt"));
    try!(f.write_all(b"Hello, world!"));

    let mut f = try!(File::open("foo.txt"));
    let mut s = String::new();
    try!(f.read_to_string(&mut s));
    assert_eq!(s, "Hello, world!");

## Methods

### `impl File`

#### `fn open<P: AsRef<Path>>(path: P) -> Result<File>`

Attempts to open a file in read-only mode.

See the `OpenOptions::open` method for more details.

# Errors

This function will return an error if `path` does not already exist. Other errors may also be returned according to `OpenOptions::open`.

# Examples

fn main() { use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::open("foo.txt")); Ok(()) } }

    use std::fs::File;

    let mut f = try!(File::open("foo.txt"));

#### `fn create<P: AsRef<Path>>(path: P) -> Result<File>`

Opens a file in write-only mode.

This function will create a file if it does not exist, and will truncate it if it does.

See the `OpenOptions::open` function for more details.

# Examples

fn main() { use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::create("foo.txt")); Ok(()) } }

    use std::fs::File;

    let mut f = try!(File::create("foo.txt"));

#### `fn sync_all(&self) -> Result<()>`

Attempts to sync all OS-internal metadata to disk.

This function will attempt to ensure that all in-core data reaches the filesystem before returning.

# Examples

fn main() { use std::fs::File; use std::io::prelude::*; fn foo() -> std::io::Result<()> { let mut f = try!(File::create("foo.txt")); try!(f.write_all(b"Hello, world!")); try!(f.sync_all()); Ok(()) } }

    use std::fs::File;
    use std::io::prelude::*;

    let mut f = try!(File::create("foo.txt"));
    try!(f.write_all(b"Hello, world!"));

    try!(f.sync_all());

#### `fn sync_data(&self) -> Result<()>`

This function is similar to `sync_all`, except that it may not synchronize file metadata to the filesystem.

This is intended for use cases that must synchronize content, but don't need the metadata on disk. The goal of this method is to reduce disk operations.

Note that some platforms may simply implement this in terms of `sync_all`.

# Examples

fn main() { use std::fs::File; use std::io::prelude::*; fn foo() -> std::io::Result<()> { let mut f = try!(File::create("foo.txt")); try!(f.write_all(b"Hello, world!")); try!(f.sync_data()); Ok(()) } }

    use std::fs::File;
    use std::io::prelude::*;

    let mut f = try!(File::create("foo.txt"));
    try!(f.write_all(b"Hello, world!"));

    try!(f.sync_data());

#### `fn set_len(&self, size: u64) -> Result<()>`

Truncates or extends the underlying file, updating the size of this file to become `size`.

If the `size` is less than the current file's size, then the file will be shrunk. If it is greater than the current file's size, then the file will be extended to `size` and have all of the intermediate data filled in with 0s.

# Errors

This function will return an error if the file is not opened for writing.

# Examples

fn main() { use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::create("foo.txt")); try!(f.set_len(10)); Ok(()) } }

    use std::fs::File;

    let mut f = try!(File::create("foo.txt"));
    try!(f.set_len(10));

#### `fn metadata(&self) -> Result<Metadata>`

Queries metadata about the underlying file.

# Examples

fn main() { use std::fs::File; fn foo() -> std::io::Result<()> { let mut f = try!(File::open("foo.txt")); let metadata = try!(f.metadata()); Ok(()) } }

    use std::fs::File;

    let mut f = try!(File::open("foo.txt"));
    let metadata = try!(f.metadata());

## Trait Implementations

### `impl Debug for File`

#### `fn fmt(&self, f: &mut Formatter) -> Result`

### `impl Read for File`

#### `fn read(&mut self, buf: &mut [u8]) -> Result<usize>`

#### `fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>`

#### `fn read_to_string(&mut self, buf: &mut String) -> Result<usize>`

#### `fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

#### `fn bytes(self) -> Bytes<Self> where Self: Sized`

#### `fn chars(self) -> Chars<Self> where Self: Sized`

#### `fn chain<R: Read>(self, next: R) -> Chain<Self, R> where Self: Sized`

#### `fn take(self, limit: u64) -> Take<Self> where Self: Sized`

#### `fn tee<W: Write>(self, out: W) -> Tee<Self, W> where Self: Sized`

### `impl Write for File`

#### `fn write(&mut self, buf: &[u8]) -> Result<usize>`

#### `fn flush(&mut self) -> Result<()>`

#### `fn write_all(&mut self, buf: &[u8]) -> Result<()>`

#### `fn write_fmt(&mut self, fmt: Arguments) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

#### `fn broadcast<W: Write>(self, other: W) -> Broadcast<Self, W> where Self: Sized`

### `impl Seek for File`

#### `fn seek(&mut self, pos: SeekFrom) -> Result<u64>`

### `impl<'a> Read for &'a File`

#### `fn read(&mut self, buf: &mut [u8]) -> Result<usize>`

#### `fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>`

#### `fn read_to_string(&mut self, buf: &mut String) -> Result<usize>`

#### `fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

#### `fn bytes(self) -> Bytes<Self> where Self: Sized`

#### `fn chars(self) -> Chars<Self> where Self: Sized`

#### `fn chain<R: Read>(self, next: R) -> Chain<Self, R> where Self: Sized`

#### `fn take(self, limit: u64) -> Take<Self> where Self: Sized`

#### `fn tee<W: Write>(self, out: W) -> Tee<Self, W> where Self: Sized`

### `impl<'a> Write for &'a File`

#### `fn write(&mut self, buf: &[u8]) -> Result<usize>`

#### `fn flush(&mut self) -> Result<()>`

#### `fn write_all(&mut self, buf: &[u8]) -> Result<()>`

#### `fn write_fmt(&mut self, fmt: Arguments) -> Result<()>`

#### `fn by_ref(&mut self) -> &mut Self where Self: Sized`

#### `fn broadcast<W: Write>(self, other: W) -> Broadcast<Self, W> where Self: Sized`

### `impl<'a> Seek for &'a File`

#### `fn seek(&mut self, pos: SeekFrom) -> Result<u64>`

### `impl AsRawFd for File`

#### `fn as_raw_fd(&self) -> RawFd`

### `impl FromRawFd for File`

#### `unsafe fn from_raw_fd(fd: RawFd) -> File`

### `impl IntoRawFd for File`

#### `fn into_raw_fd(self) -> RawFd`

### `impl AsRawFd for File`

#### `fn as_raw_fd(&self) -> RawFd`

### `impl FromRawFd for File`

#### `unsafe fn from_raw_fd(fd: RawFd) -> File`

### `impl IntoRawFd for File`

#### `fn into_raw_fd(self) -> RawFd`

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize`)