Struct FileLock

Source

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

Expand description

A locked file.

Implementations§

Source §

impl FileLock

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pub fn new_exclusive(file: File) -> Result<Self>

Take an exclusive lock on a File.

Note that this operation is blocking, and should not be called in async contexts.

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pub fn new_try_exclusive(file: File) -> Result<Self, (File, Option<Error>)>

Try to take an exclusive lock on a File.

On success returns Self. On error the original File and optionally an io::Error if the the failure was caused by anything other than the lock being taken already.

Note that this operation is blocking, and should not be called in async contexts.

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pub fn new_shared(file: File) -> Result<Self>

Take a shared lock on a File.

Note that this operation is blocking, and should not be called in async contexts.

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pub fn new_try_shared(file: File) -> Result<Self, (File, Option<Error>)>

Try to take a shared lock on a File.

On success returns Self. On error the original File and optionally an io::Error if the the failure was caused by anything other than the lock being taken already.

Note that this operation is blocking, and should not be called in async contexts.

Methods from Deref<Target = File>§

1.0.0 · Source

pub fn sync_all(&self) -> Result<(), Error>

Attempts to sync all OS-internal file content and metadata to disk.

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

This can be used to handle errors that would otherwise only be caught when the File is closed, as dropping a File will ignore all errors. Note, however, that sync_all is generally more expensive than closing a file by dropping it, because the latter is not required to block until the data has been written to the filesystem.

If synchronizing the metadata is not required, use sync_data instead.

§Examples

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

fn main() -> std::io::Result<()> {
    let mut f = File::create("foo.txt")?;
    f.write_all(b"Hello, world!")?;

    f.sync_all()?;
    Ok(())
}

1.0.0 · Source

pub fn sync_data(&self) -> Result<(), Error>

This function is similar to sync_all, except that it might 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::*;

fn main() -> std::io::Result<()> {
    let mut f = File::create("foo.txt")?;
    f.write_all(b"Hello, world!")?;

    f.sync_data()?;
    Ok(())
}

1.0.0 · Source

pub fn set_len(&self, size: u64) -> Result<(), Error>

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.

The file’s cursor isn’t changed. In particular, if the cursor was at the end and the file is shrunk using this operation, the cursor will now be past the end.

§Errors

This function will return an error if the file is not opened for writing. Also, std::io::ErrorKind::InvalidInput will be returned if the desired length would cause an overflow due to the implementation specifics.

§Examples

use std::fs::File;

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

Note that this method alters the content of the underlying file, even though it takes &self rather than &mut self.

1.0.0 · Source

pub fn metadata(&self) -> Result<Metadata, Error>

Queries metadata about the underlying file.

§Examples

use std::fs::File;

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

1.9.0 · Source

pub fn try_clone(&self) -> Result<File, Error>

Creates a new File instance that shares the same underlying file handle as the existing File instance. Reads, writes, and seeks will affect both File instances simultaneously.

§Examples

Creates two handles for a file named foo.txt:

use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let file_copy = file.try_clone()?;
    Ok(())
}

Assuming there’s a file named foo.txt with contents abcdef\n, create two handles, seek one of them, and read the remaining bytes from the other handle:

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

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let mut file_copy = file.try_clone()?;

    file.seek(SeekFrom::Start(3))?;

    let mut contents = vec![];
    file_copy.read_to_end(&mut contents)?;
    assert_eq!(contents, b"def\n");
    Ok(())
}

1.16.0 · Source

pub fn set_permissions(&self, perm: Permissions) -> Result<(), Error>

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

fn main() -> std::io::Result<()> {
    use std::fs::File;

    let file = File::open("foo.txt")?;
    let mut perms = file.metadata()?.permissions();
    perms.set_readonly(true);
    file.set_permissions(perms)?;
    Ok(())
}

Note that this method alters the permissions of the underlying file, even though it takes &self rather than &mut self.

1.75.0 · Source

pub fn set_times(&self, times: FileTimes) -> Result<(), Error>

Changes the timestamps of the underlying file.

§Platform-specific behavior

This function currently corresponds to the futimens function on Unix (falling back to futimes on macOS before 10.13) and the SetFileTime function on Windows. Note that this may change in the future.

§Errors

This function will return an error if the user lacks permission to change timestamps on the underlying file. It may also return an error in other os-specific unspecified cases.

This function may return an error if the operating system lacks support to change one or more of the timestamps set in the FileTimes structure.

§Examples

fn main() -> std::io::Result<()> {
    use std::fs::{self, File, FileTimes};

    let src = fs::metadata("src")?;
    let dest = File::options().write(true).open("dest")?;
    let times = FileTimes::new()
        .set_accessed(src.accessed()?)
        .set_modified(src.modified()?);
    dest.set_times(times)?;
    Ok(())
}