Module tokio::fs

Asynchronous file and standard stream adaptation.

This module contains utility methods and adapter types for input/output to files or standard streams (Stdin, Stdout, Stderr), and filesystem manipulation, for use within (and only within) a Tokio runtime.

Tasks run by worker threads should not block, as this could delay servicing reactor events. Portable filesystem operations are blocking, however. This module offers adapters which use a blocking annotation to inform the runtime that a blocking operation is required. When necessary, this allows the runtime to convert the current thread from a worker to a backup thread, where blocking is acceptable.

Usage

Where possible, users should prefer the provided asynchronous-specific traits such as AsyncRead, or methods returning a Future or Poll type. Adaptions also extend to traits like std::io::Read where methods return std::io::Result. Be warned that these adapted methods may return std::io::ErrorKind::WouldBlock if a worker thread can not be converted to a backup thread immediately.

Warning: These adapters may create a large number of temporary tasks, especially when reading large files. When performing a lot of operations in one batch, it may be significantly faster to use spawn_blocking directly:

use tokio::fs::File;
use std::io::{BufReader, BufRead};
async fn count_lines(file: File) -> Result<usize, std::io::Error> {
    let file = file.into_std().await;
    tokio::task::spawn_blocking(move || {
        let line_count = BufReader::new(file).lines().count();
        Ok(line_count)
    }).await?
}

Structs

• DirBuilder
  A builder for creating directories in various manners.
• DirEntry
  Entries returned by the ReadDir stream.
• File
  A reference to an open file on the filesystem.
• OpenOptions
  Options and flags which can be used to configure how a file is opened.
• ReadDir
  Reads the entries in a directory.

Functions

• canonicalize
  Returns the canonical, absolute form of a path with all intermediate components normalized and symbolic links resolved.
• copy
  Copies the contents of one file to another. This function will also copy the permission bits of the original file to the destination file. This function will overwrite the contents of to.
• create_dir
  Creates a new, empty directory at the provided path.
• create_dir_all
  Recursively creates a directory and all of its parent components if they are missing.
• hard_link
  Creates a new hard link on the filesystem.
• metadata
  Given a path, queries the file system to get information about a file, directory, etc.
• read
  Reads the entire contents of a file into a bytes vector.
• read_dir
  Returns a stream over the entries within a directory.
• read_link
  Reads a symbolic link, returning the file that the link points to.
• read_to_string
  Creates a future which will open a file for reading and read the entire contents into a string and return said string.
• remove_dir
  Removes an existing, empty directory.
• remove_dir_all
  Removes a directory at this path, after removing all its contents. Use carefully!
• remove_file
  Removes a file from the filesystem.
• rename
  Renames a file or directory to a new name, replacing the original file if to already exists.
• set_permissions
  Changes the permissions found on a file or a directory.
• symlink
  Creates a new symbolic link on the filesystem.
• symlink_metadata
  Queries the file system metadata for a path.
• try_exists
  Returns Ok(true) if the path points at an existing entity.
• write
  Creates a future that will open a file for writing and write the entire contents of contents to it.