Struct tempfile::Builder

pub struct Builder<'a, 'b> {
    pub(crate) random_len: usize,
    pub(crate) prefix: &'a OsStr,
    pub(crate) suffix: &'b OsStr,
    pub(crate) append: bool,
    pub(crate) permissions: Option<Permissions>,
}

Create a new temporary file or directory with custom parameters.

Fields

random_len: usize

prefix: &'a OsStr

suffix: &'b OsStr

append: bool

permissions: Option<Permissions>

Implementations

impl<'a, 'b> Builder<'a, 'b>

pub fn new() -> Self

Create a new Builder.

Examples

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

use tempfile::Builder;

let named_tempfile = Builder::new()
    .prefix("my-temporary-note")
    .suffix(".txt")
    .rand_bytes(5)
    .tempfile()?;

let name = named_tempfile
    .path()
    .file_name().and_then(OsStr::to_str);

if let Some(name) = name {
    assert!(name.starts_with("my-temporary-note"));
    assert!(name.ends_with(".txt"));
    assert_eq!(name.len(), "my-temporary-note.txt".len() + 5);
}

Create a temporary directory and add a file to it:

use tempfile::Builder;

let dir = Builder::new()
    .prefix("my-temporary-dir")
    .rand_bytes(5)
    .tempdir()?;

let file_path = dir.path().join("my-temporary-note.txt");
let mut file = File::create(file_path)?;
writeln!(file, "Brian was here. Briefly.")?;

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

Create a temporary directory with a chosen prefix under a chosen folder:

let dir = Builder::new()
    .prefix("my-temporary-dir")
    .tempdir_in("folder-with-tempdirs")?;

pub fn prefix<S: AsRef<OsStr> + ?Sized>(&mut self, prefix: &'a S) -> &mut Self

Set a custom filename prefix.

Path separators are legal but not advisable. Default: .tmp.

Examples

let named_tempfile = Builder::new()
    .prefix("my-temporary-note")
    .tempfile()?;

pub fn suffix<S: AsRef<OsStr> + ?Sized>(&mut self, suffix: &'b S) -> &mut Self

Set a custom filename suffix.

Path separators are legal but not advisable. Default: empty.

Examples

let named_tempfile = Builder::new()
    .suffix(".txt")
    .tempfile()?;

pub fn rand_bytes(&mut self, rand: usize) -> &mut Self

Set the number of random bytes.

Default: 6.

Examples

let named_tempfile = Builder::new()
    .rand_bytes(5)
    .tempfile()?;

pub fn append(&mut self, append: bool) -> &mut Self

Set the file to be opened in append mode.

Default: false.

Examples

let named_tempfile = Builder::new()
    .append(true)
    .tempfile()?;

pub fn permissions(&mut self, permissions: Permissions) -> &mut Self

The permissions to create the tempfile or tempdir with. This allows to them differ from the default mode of 0o600 on Unix.

Security

By default, the permissions of tempfiles on unix are set for it to be readable and writable by the owner only, yielding the greatest amount of security. As this method allows to widen the permissions, security would be reduced in such cases.

Platform Notes

Unix

The actual permission bits set on the tempfile or tempdir will be affected by the umask applied by the underlying syscall.

Windows and others

This setting is unsupported and trying to set a file or directory read-only will cause an error to be returned..

Examples

Create a named temporary file that is world-readable.

#[cfg(unix)]
{
    use std::os::unix::fs::PermissionsExt;
    let all_read_write = std::fs::Permissions::from_mode(0o666);
    let tempfile = Builder::new().permissions(all_read_write).tempfile()?;
    let actual_permissions = tempfile.path().metadata()?.permissions();
    assert_ne!(
        actual_permissions.mode() & !0o170000,
        0o600,
        "we get broader permissions than the default despite umask"
    );
}

Create a named temporary directory that is restricted to the owner.

#[cfg(unix)]
{
    use std::os::unix::fs::PermissionsExt;
    let owner_rwx = std::fs::Permissions::from_mode(0o700);
    let tempdir = Builder::new().permissions(owner_rwx).tempdir()?;
    let actual_permissions = tempdir.path().metadata()?.permissions();
    assert_eq!(
        actual_permissions.mode() & !0o170000,
        0o700,
        "we get the narrow permissions we asked for"
    );
}

pub fn tempfile(&self) -> Result<NamedTempFile>

Create the named temporary file.

Security

See the security docs on NamedTempFile.

Resource leaking

See the resource leaking docs on NamedTempFile.

Errors

If the file cannot be created, Err is returned.

Examples

let tempfile = Builder::new().tempfile()?;

pub fn tempfile_in<P: AsRef<Path>>(&self, dir: P) -> Result<NamedTempFile>

Create the named temporary file in the specified directory.

Security

See the security docs on NamedTempFile.

Resource leaking

See the resource leaking docs on NamedTempFile.

Errors

If the file cannot be created, Err is returned.

Examples

let tempfile = Builder::new().tempfile_in("./")?;

pub fn tempdir(&self) -> Result<TempDir>

Attempts to make a temporary directory inside of env::temp_dir() whose name will have the prefix, prefix. The directory and everything inside it will be automatically deleted once the returned TempDir is destroyed.

Resource leaking

See the resource leaking docs on TempDir.

Errors

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

Examples

use std::fs::File;
use std::io::Write;
use tempfile::Builder;

let tmp_dir = Builder::new().tempdir()?;

pub fn tempdir_in<P: AsRef<Path>>(&self, dir: P) -> Result<TempDir>

Attempts to make a temporary directory inside of dir. The directory and everything inside it will be automatically deleted once the returned TempDir is destroyed.

Resource leaking

See the resource leaking docs on TempDir.

Errors

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

Examples

use std::fs::{self, File};
use std::io::Write;
use tempfile::Builder;

let tmp_dir = Builder::new().tempdir_in("./")?;

pub fn make<F, R>(&self, f: F) -> Result<NamedTempFile<R>>where F: FnMut(&Path) -> Result<R>,

Attempts to create a temporary file (or file-like object) using the provided closure. The closure is passed a temporary file path and returns an std::io::Result. The path provided to the closure will be inside of std::env::temp_dir(). Use Builder::make_in to provide a custom temporary directory. If the closure returns one of the following errors, then another randomized file path is tried:

• std::io::ErrorKind::AlreadyExists
• std::io::ErrorKind::AddrInUse

This can be helpful for taking full control over the file creation, but leaving the temporary file path construction up to the library. This also enables creating a temporary UNIX domain socket, since it is not possible to bind to a socket that already exists.

Note that Builder::append is ignored when using Builder::make.

Security

This has the same security implications as NamedTempFile, but with additional caveats. Specifically, it is up to the closure to ensure that the file does not exist and that such a check is atomic. Otherwise, a time-of-check to time-of-use bug could be introduced.

For example, the following is not secure:

// This is NOT secure!
let tempfile = Builder::new().make(|path| {
    if path.is_file() {
        return Err(io::ErrorKind::AlreadyExists.into());
    }

    // Between the check above and the usage below, an attacker could
    // have replaced `path` with another file, which would get truncated
    // by `File::create`.

    File::create(path)
})?;

Note that simply using std::fs::File::create alone is not correct because it does not fail if the file already exists:

// This could overwrite an existing file!
let tempfile = Builder::new().make(|path| File::create(path))?;

For creating regular temporary files, use Builder::tempfile instead to avoid these problems. This function is meant to enable more exotic use-cases.

Resource leaking

See the resource leaking docs on NamedTempFile.

Errors

If the closure returns any error besides std::io::ErrorKind::AlreadyExists or std::io::ErrorKind::AddrInUse, then Err is returned.

Examples

use std::os::unix::net::UnixListener;
let tempsock = Builder::new().make(|path| UnixListener::bind(path))?;

pub fn make_in<F, R, P>(&self, dir: P, f: F) -> Result<NamedTempFile<R>>where F: FnMut(&Path) -> Result<R>, P: AsRef<Path>,

This is the same as Builder::make, except dir is used as the base directory for the temporary file path.

See Builder::make for more details and security implications.

Examples

use std::os::unix::net::UnixListener;
let tempsock = Builder::new().make_in("./", |path| UnixListener::bind(path))?;

Trait Implementations

impl<'a, 'b> Clone for Builder<'a, 'b>

fn clone(&self) -> Builder<'a, 'b>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a, 'b> Debug for Builder<'a, 'b>

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

Formats the value using the given formatter.

impl<'a, 'b> Default for Builder<'a, 'b>

fn default() -> Self

Returns the “default value” for a type.

impl<'a, 'b> PartialEq<Builder<'a, 'b>> for Builder<'a, 'b>

fn eq(&self, other: &Builder<'a, 'b>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a, 'b> Eq for Builder<'a, 'b>

impl<'a, 'b> StructuralEq for Builder<'a, 'b>

impl<'a, 'b> StructuralPartialEq for Builder<'a, 'b>