ErrorKind in alloc::io - Rust
Description: A list specifying general categories of I/O error.

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## ErrorKind

# Enum ErrorKind

Source

    #[non_exhaustive]pub enum ErrorKind {
    Show 42 variants    NotFound,
        PermissionDenied,
        ConnectionRefused,
        ConnectionReset,
        HostUnreachable,
        NetworkUnreachable,
        ConnectionAborted,
        NotConnected,
        AddrInUse,
        AddrNotAvailable,
        NetworkDown,
        BrokenPipe,
        AlreadyExists,
        WouldBlock,
        NotADirectory,
        IsADirectory,
        DirectoryNotEmpty,
        ReadOnlyFilesystem,
        FilesystemLoop,
        StaleNetworkFileHandle,
        InvalidInput,
        InvalidData,
        TimedOut,
        WriteZero,
        StorageFull,
        NotSeekable,
        QuotaExceeded,
        FileTooLarge,
        ResourceBusy,
        ExecutableFileBusy,
        Deadlock,
        CrossesDevices,
        TooManyLinks,
        InvalidFilename,
        ArgumentListTooLong,
        Interrupted,
        Unsupported,
        UnexpectedEof,
        OutOfMemory,
        InProgress,
        TooManyOpenFiles,
        Other,
    }

🔬This is a nightly-only experimental API. (`alloc_io` #154046)
Expand description

A list specifying general categories of I/O error.

This list is intended to grow over time and it is not recommended to exhaustively match against it.

It is used with the `io::Error` type.

## §Handling errors and matching on `ErrorKind`

In application code, use `match` for the `ErrorKind` values you are expecting; use `_` to match “all other errors”.

In comprehensive and thorough tests that want to verify that a test doesn’t return any known incorrect error kind, you may want to cut-and-paste the current full list of errors from here into your test code, and then match `_` as the correct case. This seems counterintuitive, but it will make your tests more robust. In particular, if you want to verify that your code does produce an unrecognized error kind, the robust solution is to check for all the recognized error kinds and fail in those cases.

## Variants (Non-exhaustive)§

This enum is marked as non-exhaustive
Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.
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### NotFound

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

An entity was not found, often a file.

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### PermissionDenied

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The operation lacked the necessary privileges to complete.

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### ConnectionRefused

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The connection was refused by the remote server.

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### ConnectionReset

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The connection was reset by the remote server.

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### HostUnreachable

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The remote host is not reachable.

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### NetworkUnreachable

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The network containing the remote host is not reachable.

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### ConnectionAborted

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The connection was aborted (terminated) by the remote server.

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### NotConnected

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The network operation failed because it was not connected yet.

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### AddrInUse

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A socket address could not be bound because the address is already in use elsewhere.

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### AddrNotAvailable

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A nonexistent interface was requested or the requested address was not local.

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### NetworkDown

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The system’s networking is down.

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### BrokenPipe

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The operation failed because a pipe was closed.

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### AlreadyExists

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

An entity already exists, often a file.

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### WouldBlock

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The operation needs to block to complete, but the blocking operation was requested to not occur.

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### NotADirectory

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A filesystem object is, unexpectedly, not a directory.

For example, a filesystem path was specified where one of the intermediate directory components was, in fact, a plain file.

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### IsADirectory

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The filesystem object is, unexpectedly, a directory.

A directory was specified when a non-directory was expected.

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### DirectoryNotEmpty

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A non-empty directory was specified where an empty directory was expected.

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### ReadOnlyFilesystem

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The filesystem or storage medium is read-only, but a write operation was attempted.

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### FilesystemLoop

🔬This is a nightly-only experimental API. (`io_error_more` #86442)

Loop in the filesystem or IO subsystem; often, too many levels of symbolic links.

There was a loop (or excessively long chain) resolving a filesystem object or file IO object.

On Unix this is usually the result of a symbolic link loop; or, of exceeding the system-specific limit on the depth of symlink traversal.

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### StaleNetworkFileHandle

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Stale network file handle.

With some network filesystems, notably NFS, an open file (or directory) can be invalidated by problems with the network or server.

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### InvalidInput

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A parameter was incorrect.

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### InvalidData

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Data not valid for the operation were encountered.

Unlike `InvalidInput`, this typically means that the operation parameters were valid, however the error was caused by malformed input data.

For example, a function that reads a file into a string will error with `InvalidData` if the file’s contents are not valid UTF-8.

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### TimedOut

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The I/O operation’s timeout expired, causing it to be canceled.

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### WriteZero

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

An error returned when an operation could not be completed because a call to `write` returned `Ok(0)`.

This typically means that an operation could only succeed if it wrote a particular number of bytes but only a smaller number of bytes could be written.

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### StorageFull

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

The underlying storage (typically, a filesystem) is full.

This does not include out of quota errors.

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### NotSeekable

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Seek on unseekable file.

Seeking was attempted on an open file handle which is not suitable for seeking - for example, on Unix, a named pipe opened with `File::open`.

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### QuotaExceeded

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Filesystem quota or some other kind of quota was exceeded.

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### FileTooLarge

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

File larger than allowed or supported.

This might arise from a hard limit of the underlying filesystem or file access API, or from an administratively imposed resource limitation. Simple disk full, and out of quota, have their own errors.

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### ResourceBusy

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Resource is busy.

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### ExecutableFileBusy

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Executable file is busy.

An attempt was made to write to a file which is also in use as a running program. (Not all operating systems detect this situation.)

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### Deadlock

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Deadlock (avoided).

A file locking operation would result in deadlock. This situation is typically detected, if at all, on a best-effort basis.

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### CrossesDevices

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Cross-device or cross-filesystem (hard) link or rename.

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### TooManyLinks

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Too many (hard) links to the same filesystem object.

The filesystem does not support making so many hardlinks to the same file.

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### InvalidFilename

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A filename was invalid.

This error can also occur if a length limit for a name was exceeded.

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### ArgumentListTooLong

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

Program argument list too long.

When trying to run an external program, a system or process limit on the size of the arguments would have been exceeded.

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### Interrupted

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

This operation was interrupted.

Interrupted operations can typically be retried.

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### Unsupported

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

This operation is unsupported on this platform.

This means that the operation can never succeed.

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### UnexpectedEof

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

An error returned when an operation could not be completed because an “end of file” was reached prematurely.

This typically means that an operation could only succeed if it read a particular number of bytes but only a smaller number of bytes could be read.

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### OutOfMemory

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

An operation could not be completed, because it failed to allocate enough memory.

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### InProgress

🔬This is a nightly-only experimental API. (`io_error_inprogress` #130840)

The operation was partially successful and needs to be checked later on due to not blocking.

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### TooManyOpenFiles

🔬This is a nightly-only experimental API. (`io_error_too_many_open_files` #158319)

The process or the whole system has reached its limit on the number of open files or sockets.

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### Other

🔬This is a nightly-only experimental API. (`alloc_io` #154046)

A custom error that does not fall under any other I/O error kind.

This can be used to construct your own `Error`s that do not match any `ErrorKind`.

This `ErrorKind` is not used by the standard library.

Errors from the standard library that do not fall under any of the I/O error kinds cannot be `match`ed on, and will only match a wildcard (`_`) pattern. New `ErrorKind`s might be added in the future for some of those.

## Trait Implementations§

1.0.0 · Source§

### impl Clone for ErrorKind

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#### fn clone(&self) -> ErrorKind

Returns a duplicate of the value. Read more
1.0.0 (const: unstable) · Source§

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

Performs copy-assignment from `source`. Read more
1.0.0 · Source§

### impl Copy for ErrorKind

1.0.0 · Source§

### impl Debug for ErrorKind

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

Formats the value using the given formatter. Read more
1.60.0 · Source§

### impl Display for ErrorKind

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

Shows a human-readable description of the `ErrorKind`.

This is similar to `impl Display for Error`, but doesn’t require first converting to Error.

##### §Examples

    use core::io::ErrorKind;
    assert_eq!("entity not found", ErrorKind::NotFound.to_string());

1.0.0 · Source§

### impl Eq for ErrorKind

1.14.0 · Source§

### impl From<ErrorKind> for Error

Intended for use for errors not exposed to the user, where allocating onto the heap (for normal construction via Error::new) is too costly.

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#### fn from(kind: ErrorKind) -> Error

Converts an `ErrorKind` into an `Error`.

This conversion creates a new error with a simple representation of error kind.

##### §Examples

    use std::io::{Error, ErrorKind};

    let not_found = ErrorKind::NotFound;
    let error = Error::from(not_found);
    assert_eq!("entity not found", format!("{error}"));

1.0.0 · Source§

### impl Hash for ErrorKind

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#### fn hash<__H>(&self, state: &mut __H)
where __H: Hasher,

Feeds this value into the given `Hasher`. Read more
1.3.0 · Source§

#### fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
1.0.0 · Source§

### impl Ord for ErrorKind

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#### fn cmp(&self, other: &ErrorKind) -> Ordering

This method returns an `Ordering` between `self` and `other`. Read more
1.21.0 (const: unstable) · Source§

#### fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0 (const: unstable) · Source§

#### fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0 (const: unstable) · Source§

#### fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized,

Restrict a value to a certain interval. Read more
1.0.0 · Source§

### impl PartialEq for ErrorKind

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#### fn eq(&self, other: &ErrorKind) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
1.0.0 (const: unstable) · Source§

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

Tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.0.0 · Source§

### impl PartialOrd for ErrorKind

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#### fn partial_cmp(&self, other: &ErrorKind) -> Option<Ordering>

This method returns an ordering between `self` and `other` values if one exists. Read more
1.0.0 (const: unstable) · Source§

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

Tests less than (for `self` and `other`) and is used by the `<` operator. Read more
1.0.0 (const: unstable) · Source§

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

Tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more
1.0.0 (const: unstable) · Source§

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

Tests greater than (for `self` and `other`) and is used by the `>` operator. Read more
1.0.0 (const: unstable) · Source§

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

Tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more
1.0.0 · Source§

### impl StructuralPartialEq for ErrorKind

## Auto Trait Implementations§

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### impl Freeze for ErrorKind

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### impl RefUnwindSafe for ErrorKind

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### impl Send for ErrorKind

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### impl Sync for ErrorKind

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### impl Unpin for ErrorKind

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### impl UnsafeUnpin for ErrorKind

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### impl UnwindSafe for ErrorKind

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T> ToString for T
where T: Display + ?Sized,

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#### fn to_string(&self) -> String

Converts the given value to a `String`. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.