std::fs::File
Struct std::fs::File
pub struct File { /* 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.
Files are automatically closed when they go out of scope.
Examples
Create a new file and write bytes to it:
use std::fs::File;
use std::io::prelude::*;
let mut file = File::create("foo.txt")?;
file.write_all(b"Hello, world!")?; Read the contents of a file into a String:
use std::fs::File;
use std::io::prelude::*;
let mut file = File::open("foo.txt")?;
let mut contents = String::new();
file.read_to_string(&mut contents)?;
assert_eq!(contents, "Hello, world!"); It can be more efficient to read the contents of a file with a buffered Reader. This can be accomplished with BufReader<R>:
use std::fs::File;
use std::io::BufReader;
use std::io::prelude::*;
let file = File::open("foo.txt")?;
let mut buf_reader = BufReader::new(file);
let mut contents = String::new();
buf_reader.read_to_string(&mut contents)?;
assert_eq!(contents, "Hello, world!"); Methods
impl File
[src]
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
use std::fs::File;
let mut f = 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
use std::fs::File;
let mut f = 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
use std::fs::File;
use std::io::prelude::*;
let mut f = File::create("foo.txt")?;
f.write_all(b"Hello, world!")?;
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
use std::fs::File;
use std::io::prelude::*;
let mut f = File::create("foo.txt")?;
f.write_all(b"Hello, world!")?;
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
use std::fs::File;
let mut f = File::create("foo.txt")?;
f.set_len(10)?; fn metadata(&self) -> Result<Metadata>
Queries metadata about the underlying file.
Examples
use std::fs::File;
let mut f = File::open("foo.txt")?;
let metadata = f.metadata()?; fn try_clone(&self) -> Result<File>1.9.0
Creates a new independently owned handle to the underlying file.
The returned File is a reference to the same state that this object references. Both handles will read and write with the same cursor position.
Examples
use std::fs::File;
let mut f = File::open("foo.txt")?;
let file_copy = f.try_clone()?; fn set_permissions(&self, perm: Permissions) -> Result<()>1.16.0
Changes the permissions on the underlying file.
Platform-specific behavior
This function currently corresponds to the fchmod function on Unix and the SetFileInformationByHandle function on Windows. Note that, this may change in the future.
Errors
This function will return an error if the user lacks permission change attributes on the underlying file. It may also return an error in other os-specific unspecified cases.
Examples
use std::fs::File;
let file = File::open("foo.txt")?;
let mut perms = file.metadata()?.permissions();
perms.set_readonly(true);
file.set_permissions(perms)?; Trait Implementations
impl Debug for File
[src]
fn fmt(&self, f: &mut Formatter) -> Result
Formats the value using the given formatter.
impl Read for File
[src]
fn read(&mut self, buf: &mut [u8]) -> Result<usize>
Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>
Read all bytes until EOF in this source, placing them into buf. Read more
fn read_to_string(&mut self, buf: &mut String) -> Result<usize>
Read all bytes until EOF in this source, placing them into buf. Read more
fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>1.6.0
Read the exact number of bytes required to fill buf. Read more
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
Self: Sized,
Creates a "by reference" adaptor for this instance of Read. Read more
fn bytes(self) -> Bytes<Self> where
Self: Sized,
Self: Sized,
Transforms this Read instance to an Iterator over its bytes. Read more
fn chars(self) -> Chars<Self> where
Self: Sized,
Self: Sized,
Transforms this Read instance to an Iterator over chars. Read more
fn chain<R: Read>(self, next: R) -> Chain<Self, R> where
Self: Sized,
Self: Sized,
Creates an adaptor which will chain this stream with another. Read more
fn take(self, limit: u64) -> Take<Self> where
Self: Sized,
Self: Sized,
Creates an adaptor which will read at most limit bytes from it. Read more
impl Write for File
[src]
fn write(&mut self, buf: &[u8]) -> Result<usize>
Write a buffer into this object, returning how many bytes were written. Read more
fn flush(&mut self) -> Result<()>
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
fn write_all(&mut self, buf: &[u8]) -> Result<()>
Attempts to write an entire buffer into this write. Read more
fn write_fmt(&mut self, fmt: Arguments) -> Result<()>
Writes a formatted string into this writer, returning any error encountered. Read more
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
Self: Sized,
Creates a "by reference" adaptor for this instance of Write. Read more
impl Seek for File
[src]
fn seek(&mut self, pos: SeekFrom) -> Result<u64>
Seek to an offset, in bytes, in a stream. Read more
impl<'a> Read for &'a File
[src]
fn read(&mut self, buf: &mut [u8]) -> Result<usize>
Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>
Read all bytes until EOF in this source, placing them into buf. Read more
fn read_to_string(&mut self, buf: &mut String) -> Result<usize>
Read all bytes until EOF in this source, placing them into buf. Read more
fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>1.6.0
Read the exact number of bytes required to fill buf. Read more
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
Self: Sized,
Creates a "by reference" adaptor for this instance of Read. Read more
fn bytes(self) -> Bytes<Self> where
Self: Sized,
Self: Sized,
Transforms this Read instance to an Iterator over its bytes. Read more
fn chars(self) -> Chars<Self> where
Self: Sized,
Self: Sized,
Transforms this Read instance to an Iterator over chars. Read more
fn chain<R: Read>(self, next: R) -> Chain<Self, R> where
Self: Sized,
Self: Sized,
Creates an adaptor which will chain this stream with another. Read more
fn take(self, limit: u64) -> Take<Self> where
Self: Sized,
Self: Sized,
Creates an adaptor which will read at most limit bytes from it. Read more
impl<'a> Write for &'a File
[src]
fn write(&mut self, buf: &[u8]) -> Result<usize>
Write a buffer into this object, returning how many bytes were written. Read more
fn flush(&mut self) -> Result<()>
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
fn write_all(&mut self, buf: &[u8]) -> Result<()>
Attempts to write an entire buffer into this write. Read more
fn write_fmt(&mut self, fmt: Arguments) -> Result<()>
Writes a formatted string into this writer, returning any error encountered. Read more
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
Self: Sized,
Creates a "by reference" adaptor for this instance of Write. Read more
impl<'a> Seek for &'a File
[src]
fn seek(&mut self, pos: SeekFrom) -> Result<u64>
Seek to an offset, in bytes, in a stream. Read more
impl AsRawFd for File
[src]
fn as_raw_fd(&self) -> RawFd
Extracts the raw file descriptor. Read more
impl FromRawFd for File
1.1.0
[src]
unsafe fn from_raw_fd(fd: RawFd) -> File
Constructs a new instance of Self from the given raw file descriptor. Read more
impl IntoRawFd for File
1.4.0
[src]
fn into_raw_fd(self) -> RawFd
Consumes this object, returning the raw underlying file descriptor. Read more
impl FileExt for File
1.15.0
[src]
fn read_at(&self, buf: &mut [u8], offset: u64) -> Result<usize>
Reads a number of bytes starting from a given offset. Read more
fn write_at(&self, buf: &[u8], offset: u64) -> Result<usize>
Writes a number of bytes starting from a given offset. Read more
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/fs/struct.File.html
