Struct rhit::File1.0.0[−][src]

pub struct File { /* fields omitted */ }
Expand description

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. Errors detected on closing are ignored by the implementation of Drop. Use the method sync_all if these errors must be manually handled.

Examples

Creates a new file and write bytes to it (you can also use write()):

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

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

Read the contents of a file into a String (you can also use read):

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

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;
    assert_eq!(contents, "Hello, world!");
    Ok(())
}

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::*;

fn main() -> std::io::Result<()> {
    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!");
    Ok(())
}

Note that, although read and write methods require a &mut File, because of the interfaces for Read and Write, the holder of a &File can still modify the file, either through methods that take &File or by retrieving the underlying OS object and modifying the file that way. Additionally, many operating systems allow concurrent modification of files by different processes. Avoid assuming that holding a &File means that the file will not change.

Implementations

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;

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

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;

fn main() -> std::io::Result<()> {
    let mut f = File::create("foo.txt")?;
    Ok(())
}
🔬 This is a nightly-only experimental API. (with_options)

Returns a new OpenOptions object.

This function returns a new OpenOptions object that you can use to open or create a file with specific options if open() or create() are not appropriate.

It is equivalent to OpenOptions::new() but allows you to write more readable code. Instead of OpenOptions::new().read(true).open("foo.txt") you can write File::with_options().read(true).open("foo.txt"). This also avoids the need to import OpenOptions.

See the OpenOptions::new function for more details.

Examples

#![feature(with_options)]
use std::fs::File;

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

Attempts to sync all OS-internal 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. Dropping a file will ignore errors in synchronizing this in-memory data.

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(())
}

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::*;

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

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

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.

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(())
}

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(())
}

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.

Trait Implementations

Extracts the raw file descriptor. Read more

Formats the value using the given formatter. Read more

Reads a number of bytes starting from a given offset. Read more

Writes a number of bytes starting from a given offset. Read more

Reads the exact number of byte required to fill buf from the given offset. Read more

Attempts to write an entire buffer starting from a given offset. Read more

Constructs a new instance of Self from the given raw file descriptor. Read more

Consumes this object, returning the raw underlying file descriptor. Read more

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

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

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

Determines if this Reader has an efficient read_vectored implementation. Read more

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

Determines if this Reader can work with buffers of uninitialized memory. Read more

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

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

Read the exact number of bytes required to fill buf. Read more

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

Transforms this Read instance to an Iterator over its bytes. Read more

Creates an adaptor which will chain this stream with another. Read more

Creates an adaptor which will read at most limit bytes from it. Read more

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

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

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

Determines if this Reader has an efficient read_vectored implementation. Read more

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

Determines if this Reader can work with buffers of uninitialized memory. Read more

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

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

Read the exact number of bytes required to fill buf. Read more

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

Transforms this Read instance to an Iterator over its bytes. Read more

Creates an adaptor which will chain this stream with another. Read more

Creates an adaptor which will read at most limit bytes from it. Read more

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

Rewind to the beginning of a stream. Read more

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

Returns the length of this stream (in bytes). Read more

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

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

Rewind to the beginning of a stream. Read more

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

Returns the length of this stream (in bytes). Read more

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

Write a buffer into this writer, returning how many bytes were written. Read more

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

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

Determines if this Writer has an efficient write_vectored implementation. Read more

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

Attempts to write an entire buffer into this writer. Read more

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

Attempts to write multiple buffers into this writer. Read more

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

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

Write a buffer into this writer, returning how many bytes were written. Read more

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

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

Determines if this Writer has an efficient write_vectored implementation. Read more

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

Attempts to write an entire buffer into this writer. Read more

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

Attempts to write multiple buffers into this writer. Read more

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

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

Formats the provided number according to the provided format and then writes the resulting bytes to the object. Meant to be analagous to io::Write’s write_all method or fmt::Write’s write_str method. On success, returns the number of bytes written. Read more

Formats the provided number according to the provided format and then writes the resulting bytes to the object. Meant to be analagous to io::Write’s write_all method or fmt::Write’s write_str method. On success, returns the number of bytes written. Read more

Formats the provided number according to the provided format and then writes the resulting bytes to the object. Meant to be analagous to io::Write’s write_all method or fmt::Write’s write_str method. On success, returns the number of bytes written. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Executes the given command directly.

The given command its ANSI escape code will be written and flushed onto Self.

Arguments

  • Command

    The command that you want to execute directly.

Example

use std::io::{Write, stdout};

use crossterm::{Result, ExecutableCommand, style::Print};

 fn main() -> Result<()> {
     // will be executed directly
      stdout()
        .execute(Print("sum:\n".to_string()))?
        .execute(Print(format!("1 + 1= {} ", 1 + 1)))?;

      Ok(())

     // ==== Output ====
     // sum:
     // 1 + 1 = 2
 }

Have a look over at the Command API for more details.

Notes

  • In the case of UNIX and Windows 10, ANSI codes are written to the given ‘writer’.
  • In case of Windows versions lower than 10, a direct WinAPI call will be made. The reason for this is that Windows versions lower than 10 do not support ANSI codes, and can therefore not be written to the given writer. Therefore, there is no difference between execute and queue for those old Windows versions.

Performs the conversion.

Performs the conversion.

Returns true when an instance is a terminal teletype, otherwise false.

The alignment of pointer.

The type for initializers.

Initializes a with the given initializer. Read more

Dereferences the given pointer. Read more

Mutably dereferences the given pointer. Read more

Drops the object pointed to by the given pointer. Read more

Queues the given command for further execution.

Queued commands will be executed in the following cases:

  • When flush is called manually on the given type implementing io::Write.
  • The terminal will flush automatically if the buffer is full.
  • Each line is flushed in case of stdout, because it is line buffered.

Arguments

  • Command

    The command that you want to queue for later execution.

Examples

use std::io::{Write, stdout};

use crossterm::{Result, QueueableCommand, style::Print};

 fn main() -> Result<()> {
    let mut stdout = stdout();

    // `Print` will executed executed when `flush` is called.
    stdout
        .queue(Print("foo 1\n".to_string()))?
        .queue(Print("foo 2".to_string()))?;

    // some other code (no execution happening here) ...

    // when calling `flush` on `stdout`, all commands will be written to the stdout and therefore executed.
    stdout.flush()?;

    Ok(())

    // ==== Output ====
    // foo 1
    // foo 2
}

Have a look over at the Command API for more details.

Notes

  • In the case of UNIX and Windows 10, ANSI codes are written to the given ‘writer’.
  • In case of Windows versions lower than 10, a direct WinAPI call will be made. The reason for this is that Windows versions lower than 10 do not support ANSI codes, and can therefore not be written to the given writer. Therefore, there is no difference between execute and queue for those old Windows versions.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.