Struct tempfile::file::NamedTempFile[][src]

pub struct NamedTempFile {
    path: TempPath,
    file: File,
}
Expand description

A named temporary file.

The default constructor, NamedTempFile::new(), creates files in the location returned by std::env::temp_dir(), but NamedTempFile can be configured to manage a temporary file in any location by constructing with NamedTempFile::new_in().

Security

Most operating systems employ temporary file cleaners to delete old temporary files. Unfortunately these temporary file cleaners don’t always reliably detect whether the temporary file is still being used.

Specifically, the following sequence of events can happen:

  1. A user creates a temporary file with NamedTempFile::new().
  2. Time passes.
  3. The temporary file cleaner deletes (unlinks) the temporary file from the filesystem.
  4. Some other program creates a new file to replace this deleted temporary file.
  5. The user tries to re-open the temporary file (in the same program or in a different program) by path. Unfortunately, they’ll end up opening the file created by the other program, not the original file.

Operating System Specific Concerns

The behavior of temporary files and temporary file cleaners differ by operating system.

Windows

On Windows, open files can’t be deleted. This removes most of the concerns around temporary file cleaners.

Furthermore, temporary files are, by default, created in per-user temporary file directories so only an application running as the same user would be able to interfere (which they could do anyways). However, an application running as the same user can still accidentally re-create deleted temporary files if the number of random bytes in the temporary file name is too small.

So, the only real concern on Windows is:

  1. Opening a named temporary file in a world-writable directory.
  2. Using the into_temp_path() and/or into_parts() APIs to close the file handle without deleting the underlying file.
  3. Continuing to use the file by path.

UNIX

Unlike on Windows, UNIX (and UNIX like) systems allow open files to be “unlinked” (deleted).

MacOS

Like on Windows, temporary files are created in per-user temporary file directories by default so calling NamedTempFile::new() should be relatively safe.

Linux

Unfortunately, most Linux distributions don’t create per-user temporary file directories. Worse, systemd’s tmpfiles daemon (a common temporary file cleaner) will happily remove open temporary files if they haven’t been modified within the last 10 days.

Resource Leaking

If the program exits before the NamedTempFile destructor is run, such as via std::process::exit(), by segfaulting, or by receiving a signal like SIGINT, then the temporary file will not be deleted.

Use the tempfile() function unless you absolutely need a named file.

Fields

path: TempPathfile: File

Implementations

Create a new named temporary file.

See Builder for more configuration.

Security

This will create a temporary file in the default temporary file directory (platform dependent). This has security implications on many platforms so please read the security section of this type’s documentation.

Reasons to use this method:

  1. The file has a short lifetime and your temporary file cleaner is sane (doesn’t delete recently accessed files).

  2. You trust every user on your system (i.e. you are the only user).

  3. You have disabled your system’s temporary file cleaner or verified that your system doesn’t have a temporary file cleaner.

Reasons not to use this method:

  1. You’ll fix it later. No you won’t.

  2. You don’t care about the security of the temporary file. If none of the “reasons to use this method” apply, referring to a temporary file by name may allow an attacker to create/overwrite your non-temporary files. There are exceptions but if you don’t already know them, don’t use this method.

Errors

If the file can not be created, Err is returned.

Examples

Create a named temporary file and write some data to it:

use tempfile::NamedTempFile;

let mut file = NamedTempFile::new()?;

writeln!(file, "Brian was here. Briefly.")?;

Create a new named temporary file in the specified directory.

See NamedTempFile::new() for details.

Get the temporary file’s path.

Security

Referring to a temporary file’s path may not be secure in all cases. Please read the security section on the top level documentation of this type for details.

Examples
use tempfile::NamedTempFile;

let file = NamedTempFile::new()?;

println!("{:?}", file.path());

Close and remove the temporary file.

Use this if you want to detect errors in deleting the file.

Errors

If the file cannot be deleted, Err is returned.

Examples
use tempfile::NamedTempFile;

let file = NamedTempFile::new()?;

// By closing the `NamedTempFile` explicitly, we can check that it has
// been deleted successfully. If we don't close it explicitly,
// the file will still be deleted when `file` goes out
// of scope, but we won't know whether deleting the file
// succeeded.
file.close()?;

Persist the temporary file at the target path.

If a file exists at the target path, persist will atomically replace it. If this method fails, it will return self in the resulting PersistError.

Note: Temporary files cannot be persisted across filesystems.

Security

This method persists the temporary file using it’s path and may not be secure in the in all cases. Please read the security section on the top level documentation of this type for details.

Errors

If the file cannot be moved to the new location, Err is returned.

Examples
use tempfile::NamedTempFile;

let file = NamedTempFile::new()?;

let mut persisted_file = file.persist("./saved_file.txt")?;
writeln!(persisted_file, "Brian was here. Briefly.")?;

Persist the temporary file at the target path iff no file exists there.

If a file exists at the target path, fail. If this method fails, it will return self in the resulting PersistError.

Note: Temporary files cannot be persisted across filesystems. Also Note: This method is not atomic. It can leave the original link to the temporary file behind.

Security

This method persists the temporary file using it’s path and may not be secure in the in all cases. Please read the security section on the top level documentation of this type for details.

Errors

If the file cannot be moved to the new location or a file already exists there, Err is returned.

Examples
use tempfile::NamedTempFile;

let file = NamedTempFile::new()?;

let mut persisted_file = file.persist_noclobber("./saved_file.txt")?;
writeln!(persisted_file, "Brian was here. Briefly.")?;

Keep the temporary file from being deleted. This function will turn the temporary file into a non-temporary file without moving it.

Errors

On some platforms (e.g., Windows), we need to mark the file as non-temporary. This operation could fail.

Examples
use tempfile::NamedTempFile;

let mut file = NamedTempFile::new()?;
writeln!(file, "Brian was here. Briefly.")?;

let (file, path) = file.keep()?;

Securely reopen the temporary file.

This function is useful when you need multiple independent handles to the same file. It’s perfectly fine to drop the original NamedTempFile while holding on to Files returned by this function; the Files will remain usable. However, they may not be nameable.

Errors

If the file cannot be reopened, Err is returned.

Security

Unlike File::open(my_temp_file.path()), NamedTempFile::reopen() guarantees that the re-opened file is the same file, even in the presence of pathological temporary file cleaners.

Examples
use tempfile::NamedTempFile;

let file = NamedTempFile::new()?;

let another_handle = file.reopen()?;

Get a reference to the underlying file.

Get a mutable reference to the underlying file.

Convert the temporary file into a std::fs::File.

The inner file will be deleted.

Closes the file, leaving only the temporary file path.

This is useful when another process must be able to open the temporary file.

Converts the named temporary file into its constituent parts.

Note: When the path is dropped, the file is deleted but the file handle is still usable.

Trait Implementations

Extracts the raw file descriptor. Read more

Performs the conversion.

Formats the value using the given formatter. Read more

Performs the conversion.

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” adapter for this instance of Read. Read more

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

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

Creates an adapter 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” adapter for this instance of Read. Read more

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

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

Creates an adapter 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

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

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” adapter for this instance of Write. Read more

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

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

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” adapter for this instance of Write. 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

Performs the conversion.

Performs the conversion.

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.