Struct TempFile

pub struct TempFile { /* private fields */ }

A temporary file that is automatically deleted when dropped unless explicitly closed.

The file is opened with read and write permissions. When the instance is dropped, the underlying file is removed unless deletion is disarmed (for example, by calling close or into_inner).

Implementations

impl TempFile

pub fn new<P: AsRef<Path>>(path: P) -> TempResult<TempFile>

Creates a new temporary file at the specified path.

The file is created with read and write permissions.

Arguments

• path - The path at which to create the file. If a relative path is provided, it is resolved relative to the system temporary directory.

Errors

Returns an error if the file cannot be created.

Examples found in repository

ex/e3.rs (line 6)

fn main() -> Result<(), TempError> {
    // Create a temporary file at a given path.
    let mut temp_file = TempFile::new("mmap_example.txt")?;
    write!(temp_file, "This is a memory-mapped file example")?;
    temp_file.seek(SeekFrom::Start(0))?;

    // Create a read-only memory mapping.
    #[cfg(feature = "mmap_support")]
    unsafe {
        let mmap = temp_file.mmap()?;
        let content = std::str::from_utf8(&mmap)
            .unwrap_or("Invalid UTF-8 sequence");
        println!("Memory-mapped content: {content}");
    }

    Ok(())
}

pub fn new_here<P: AsRef<Path>>(path: P) -> TempResult<TempFile>

Creates a new temporary file at the specified path.

The file is created with read and write permissions.

Arguments

• path - The path at which to create the file. If a relative path is provided, it is resolved relative to the current working directory.

Errors

Returns an error if the file cannot be created.

pub fn persist(&mut self) -> TempResult<File>

Converts the TempFile into a permanent file.

Errors

Returns an error if the inner file is None.

pub fn persist_name<S: AsRef<str>>(&mut self, name: S) -> TempResult<File>

Renames the temporary file and then persists it.

Errors

Returns an error if renaming or persisting the file fails.

pub fn persist_here<S: AsRef<str>>(&mut self, name: S) -> TempResult<File>

Renames the temporary file (in the current directory) and persists it.

Errors

Returns an error if renaming or persisting the file fails.

Examples found in repository

ex/e1.rs (line 24)

fn main() -> Result<(), TempError> {
    // Create a temporary file with a random name in the system's temp directory.
    #[cfg(feature = "rand_gen")]
    let mut temp_file = TempFile::new_random::<std::path::PathBuf>(None)?;
    #[cfg(not(feature = "rand_gen"))]
    let mut temp_file = TempFile::new("./tmp/hello.txt")?;

    // Write some data to the temporary file.
    write!(temp_file, "Hello, temporary world!")?;

    // Move back to the start of the file before reading.
    temp_file.seek(SeekFrom::Start(0))?;

    // Read the file content into a string.
    let mut content = String::new();
    temp_file.read_to_string(&mut content)?;
    println!("Temp file content: {content}");

    // Rename the file (for example, to "output.txt") and persist it,
    // so that it is not deleted when `temp_file` is dropped.
    let _permanent_file = temp_file.persist_here("output.txt")?;
    println!("Temporary file persisted as output.txt");

    Ok(())
}

pub fn new_random<P: AsRef<Path>>(dir: Option<P>) -> TempResult<Self>

Creates a new temporary file with a random name in the given directory.

The file name is generated using random ASCII characters.

Arguments

• dir - The directory in which to create the file. If None, the system temporary directory is used. If a relative directory is provided, it is resolved relative to the system temporary directory.

Errors

Returns an error if a unique filename cannot be generated or if file creation fails.

Examples found in repository

ex/e1.rs (line 7)

fn main() -> Result<(), TempError> {
    // Create a temporary file with a random name in the system's temp directory.
    #[cfg(feature = "rand_gen")]
    let mut temp_file = TempFile::new_random::<std::path::PathBuf>(None)?;
    #[cfg(not(feature = "rand_gen"))]
    let mut temp_file = TempFile::new("./tmp/hello.txt")?;

    // Write some data to the temporary file.
    write!(temp_file, "Hello, temporary world!")?;

    // Move back to the start of the file before reading.
    temp_file.seek(SeekFrom::Start(0))?;

    // Read the file content into a string.
    let mut content = String::new();
    temp_file.read_to_string(&mut content)?;
    println!("Temp file content: {content}");

    // Rename the file (for example, to "output.txt") and persist it,
    // so that it is not deleted when `temp_file` is dropped.
    let _permanent_file = temp_file.persist_here("output.txt")?;
    println!("Temporary file persisted as output.txt");

    Ok(())
}

pub fn new_random_here<P: AsRef<Path>>(dir: Option<P>) -> TempResult<Self>

Creates a new temporary file with a random name in the given directory.

The file name is generated using random ASCII characters.

Arguments

• dir - The directory in which to create the file. If None, the current working directory is used. If a relative directory is provided, it is resolved relative to the current directory.

Errors

Returns an error if a unique filename cannot be generated or if file creation fails.

pub fn file_mut(&mut self) -> TempResult<&mut File>

Returns a mutable reference to the file handle.

Errors

Returns Err(TempError::FileIsNone) if the file handle is not available.

pub fn file(&self) -> TempResult<&File>

Returns an immutable reference to the file handle.

Errors

Returns Err(TempError::FileIsNone) if the file handle is not available.

pub fn path(&self) -> Option<&Path>

Returns the path to the temporary file.

Examples found in repository

ex/e2.rs (line 30)

fn main() -> Result<(), TempError> {
    // Create a temporary directory with a random name.
    let mut temp_dir = TempDir::new_random::<std::path::PathBuf>(None)?;

    // Create a temporary file with a specific name.
    {
        let file = temp_dir.create_file("test1.txt")?;
        write!(file, "Content for test1")?;
    }

    // Create another temporary file with a random name.
    {
        let file = temp_dir.create_random_file()?;
        write!(file, "Random file content")?;
    }

    // List all the temporary files managed by the directory.
    for file_path in temp_dir.list_files() {
        println!("Managed temp file: {file_path:?}");
    }

    // If the library was built with regex support, search for files matching a pattern.
    #[cfg(feature = "regex_support")]
    {
        let matching_files = temp_dir.find_files_by_pattern(r"^test\d\.txt$")?;
        for file in matching_files {
            if let Some(path) = file.path() {
                println!("Found file matching regex: {path:?}");
            }
        }
    }

    // When `temp_dir` goes out of scope, the directory and all its managed files are automatically deleted.
    Ok(())
}

pub fn rename<P: AsRef<Path>>(&mut self, new_path: P) -> TempResult<()>

Renames the temporary file.

Arguments

• new_path - The new path for the file. If relative, its new path will be its old path’s parent, followed by this. See rename_here for a method which renames relative paths to the current directory.

Errors

Returns an error if the rename operation fails or the old path has no parent and the new path is relative.

pub fn rename_here<P: AsRef<Path>>(&mut self, new_path: P) -> TempResult<()>

Renames the temporary file using the current directory.

Arguments

• new_path - The new path for the file. If relative, its new path will be the current directory, followed by this. See rename for a method which renames relative paths to the old directory.

Errors

Returns an error if the rename operation fails.

pub fn sync_all(&self) -> TempResult<()>

Synchronizes the file’s state with the storage device.

This is generally not needed. File::sync_all for its purpose.

Errors

Returns Err(TempError::FileIsNone) if the file handle is not available, or if syncing fails.

pub fn disarm(self) -> TempResult<()>

Flushes the file and disarms automatic deletion.

After calling this method, the file will not be deleted when the TempFile is dropped.

Errors

Returns an error if flushing fails or if the file handle is not available.

pub fn close(self) -> TempResult<()>

Flushes and closes the file, disarming deletion.

After calling this method, the file will not be deleted when the TempFile is dropped.

Errors

Returns an error if flushing fails or if the file handle is not available.

pub fn into_inner(self) -> TempResult<File>

Consumes the TempFile and returns the inner file handle.

This method disarms automatic deletion.

Errors

Returns Err(TempError::FileIsNone) if the file handle has already been taken.

pub fn is_active(&self) -> bool

Checks if the file is still active.

pub fn delete(self) -> TempResult<()>

Deletes the temporary file immediately.

This method flushes the file, removes it from the filesystem, and disarms automatic deletion.

Errors

Returns an error if flushing fails, if the file handle is not available, or if file removal fails.

pub fn metadata(&self) -> TempResult<Metadata>

Retrieves metadata of the file.

Errors

Returns an error if the metadata cannot be accessed or if the file has been closed.

pub fn from_fp<P: AsRef<Path>>(file: File, path: P) -> TempResult<Self>

A function to convert a normal File and its path into a TempFile.

Errors

Returns an error if the Path and File do not point to the same file.

impl TempFile

pub unsafe fn mmap(&self) -> TempResult<Mmap>

Creates a read-only memory map of the file.

Safety

This operation is unsafe because it relies on the underlying file not changing unexpectedly.

Errors

Returns an error if mapping the file fails.

Examples found in repository

ex/e3.rs (line 13)

fn main() -> Result<(), TempError> {
    // Create a temporary file at a given path.
    let mut temp_file = TempFile::new("mmap_example.txt")?;
    write!(temp_file, "This is a memory-mapped file example")?;
    temp_file.seek(SeekFrom::Start(0))?;

    // Create a read-only memory mapping.
    #[cfg(feature = "mmap_support")]
    unsafe {
        let mmap = temp_file.mmap()?;
        let content = std::str::from_utf8(&mmap)
            .unwrap_or("Invalid UTF-8 sequence");
        println!("Memory-mapped content: {content}");
    }

    Ok(())
}

pub unsafe fn mmap_mut(&mut self) -> TempResult<MmapMut>

Creates a mutable memory map of the file.

Safety

This operation is unsafe because it allows mutable access to the file’s contents.

Errors

Returns an error if mapping the file fails.

Methods from Deref<Target = File>

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(())
}

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(())
}

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

Acquire an exclusive lock on the file. Blocks until the lock can be acquired.

This acquires an exclusive lock; no other file handle to this file may acquire another lock.

This lock may be advisory or mandatory. This lock is meant to interact with lock, try_lock, lock_shared, try_lock_shared, and unlock. Its interactions with other methods, such as read and write are platform specific, and it may or may not cause non-lockholders to block.

If this file handle/descriptor, or a clone of it, already holds an lock the exact behavior is unspecified and platform dependent, including the possibility that it will deadlock. However, if this method returns, then an exclusive lock is held.

If the file not open for writing, it is unspecified whether this function returns an error.

The lock will be released when this file (along with any other file descriptors/handles duplicated or inherited from it) is closed, or if the unlock method is called.

Platform-specific behavior

This function currently corresponds to the flock function on Unix with the LOCK_EX flag, and the LockFileEx function on Windows with the LOCKFILE_EXCLUSIVE_LOCK flag. Note that, this may change in the future.

On Windows, locking a file will fail if the file is opened only for append. To lock a file, open it with one of .read(true), .read(true).append(true), or .write(true).

Examples

use std::fs::File;

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

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

Acquire a shared (non-exclusive) lock on the file. Blocks until the lock can be acquired.

This acquires a shared lock; more than one file handle may hold a shared lock, but none may hold an exclusive lock at the same time.

This lock may be advisory or mandatory. This lock is meant to interact with lock, try_lock, lock_shared, try_lock_shared, and unlock. Its interactions with other methods, such as read and write are platform specific, and it may or may not cause non-lockholders to block.

If this file handle/descriptor, or a clone of it, already holds an lock, the exact behavior is unspecified and platform dependent, including the possibility that it will deadlock. However, if this method returns, then a shared lock is held.

The lock will be released when this file (along with any other file descriptors/handles duplicated or inherited from it) is closed, or if the unlock method is called.

Platform-specific behavior

This function currently corresponds to the flock function on Unix with the LOCK_SH flag, and the LockFileEx function on Windows. Note that, this may change in the future.

On Windows, locking a file will fail if the file is opened only for append. To lock a file, open it with one of .read(true), .read(true).append(true), or .write(true).

Examples

use std::fs::File;

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

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

Try to acquire an exclusive lock on the file.

Returns Ok(false) if a different lock is already held on this file (via another handle/descriptor).

This acquires an exclusive lock; no other file handle to this file may acquire another lock.

This lock may be advisory or mandatory. This lock is meant to interact with lock, try_lock, lock_shared, try_lock_shared, and unlock. Its interactions with other methods, such as read and write are platform specific, and it may or may not cause non-lockholders to block.

If this file handle/descriptor, or a clone of it, already holds an lock, the exact behavior is unspecified and platform dependent, including the possibility that it will deadlock. However, if this method returns Ok(true), then it has acquired an exclusive lock.

If the file not open for writing, it is unspecified whether this function returns an error.

The lock will be released when this file (along with any other file descriptors/handles duplicated or inherited from it) is closed, or if the unlock method is called.

Platform-specific behavior

This function currently corresponds to the flock function on Unix with the LOCK_EX and LOCK_NB flags, and the LockFileEx function on Windows with the LOCKFILE_EXCLUSIVE_LOCK and LOCKFILE_FAIL_IMMEDIATELY flags. Note that, this may change in the future.

On Windows, locking a file will fail if the file is opened only for append. To lock a file, open it with one of .read(true), .read(true).append(true), or .write(true).

Examples

use std::fs::File;

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

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

Try to acquire a shared (non-exclusive) lock on the file.

Returns Ok(false) if an exclusive lock is already held on this file (via another handle/descriptor).

This acquires a shared lock; more than one file handle may hold a shared lock, but none may hold an exclusive lock at the same time.

This lock may be advisory or mandatory. This lock is meant to interact with lock, try_lock, lock_shared, try_lock_shared, and unlock. Its interactions with other methods, such as read and write are platform specific, and it may or may not cause non-lockholders to block.

If this file handle, or a clone of it, already holds an lock, the exact behavior is unspecified and platform dependent, including the possibility that it will deadlock. However, if this method returns Ok(true), then it has acquired a shared lock.

The lock will be released when this file (along with any other file descriptors/handles duplicated or inherited from it) is closed, or if the unlock method is called.

Platform-specific behavior

This function currently corresponds to the flock function on Unix with the LOCK_SH and LOCK_NB flags, and the LockFileEx function on Windows with the LOCKFILE_FAIL_IMMEDIATELY flag. Note that, this may change in the future.

On Windows, locking a file will fail if the file is opened only for append. To lock a file, open it with one of .read(true), .read(true).append(true), or .write(true).

Examples

use std::fs::File;

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

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

Release all locks on the file.

All locks are released when the file (along with any other file descriptors/handles duplicated or inherited from it) is closed. This method allows releasing locks without closing the file.

If no lock is currently held via this file descriptor/handle, this method may return an error, or may return successfully without taking any action.

Platform-specific behavior

This function currently corresponds to the flock function on Unix with the LOCK_UN flag, and the UnlockFile function on Windows. Note that, this may change in the future.

On Windows, locking a file will fail if the file is opened only for append. To lock a file, open it with one of .read(true), .read(true).append(true), or .write(true).

Examples

use std::fs::File;

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

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.

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(())
}

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(())
}

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.

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(())
}

pub fn set_modified(&self, time: SystemTime) -> Result<(), Error>

Changes the modification time of the underlying file.

This is an alias for set_times(FileTimes::new().set_modified(time)).

Trait Implementations

impl AsRawFd for TempFile

fn as_raw_fd(&self) -> RawFd

Extracts the raw file descriptor.

impl AsRef<Path> for TempFile

fn as_ref(&self) -> &Path

Converts this type into a shared reference of the (usually inferred) input type.

impl Debug for TempFile

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Deref for TempFile

type Target = File

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl DerefMut for TempFile

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl Drop for TempFile

fn drop(&mut self)

Executes the destructor for this type.

impl Read for TempFile

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.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

Like read, except that it reads into a slice of buffers.

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

Reads all bytes until EOF in this source, placing them into buf.

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

Reads all bytes until EOF in this source, appending them to buf.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

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

Reads the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Reads the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

impl Seek for TempFile

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

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position.

impl Write for TempFile

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

Writes a buffer into this writer, returning how many bytes were written.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>

Like write, except that it writes from a slice of buffers.

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

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

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

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.