Struct std::fs::File
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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());