Copyright | (c) The University of Glasgow 2001 |
---|---|
License | BSD-style (see the file libraries/base/LICENSE) |
Maintainer | [email protected] |
Stability | provisional |
Portability | portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Standard IO Errors.
type IOError = IOException Source
The Haskell 2010 type for exceptions in the IO
monad. Any I/O operation may raise an IOError
instead of returning a result. For a more general type of exception, including also those that arise in pure code, see Exception
.
In Haskell 2010, this is an opaque type.
userError :: String -> IOError Source
Construct an IOError
value with a string describing the error. The fail
method of the IO
instance of the Monad
class raises a userError
, thus:
instance Monad IO where ... fail s = ioError (userError s)
mkIOError :: IOErrorType -> String -> Maybe Handle -> Maybe FilePath -> IOError Source
Construct an IOError
of the given type where the second argument describes the error location and the third and fourth argument contain the file handle and file path of the file involved in the error if applicable.
annotateIOError :: IOError -> String -> Maybe Handle -> Maybe FilePath -> IOError Source
Adds a location description and maybe a file path and file handle to an IOError
. If any of the file handle or file path is not given the corresponding value in the IOError
remains unaltered.
isAlreadyExistsError :: IOError -> Bool Source
An error indicating that an IO
operation failed because one of its arguments already exists.
isDoesNotExistError :: IOError -> Bool Source
An error indicating that an IO
operation failed because one of its arguments does not exist.
isAlreadyInUseError :: IOError -> Bool Source
An error indicating that an IO
operation failed because one of its arguments is a single-use resource, which is already being used (for example, opening the same file twice for writing might give this error).
isFullError :: IOError -> Bool Source
An error indicating that an IO
operation failed because the device is full.
isEOFError :: IOError -> Bool Source
An error indicating that an IO
operation failed because the end of file has been reached.
isIllegalOperation :: IOError -> Bool Source
An error indicating that an IO
operation failed because the operation was not possible. Any computation which returns an IO
result may fail with isIllegalOperation
. In some cases, an implementation will not be able to distinguish between the possible error causes. In this case it should fail with isIllegalOperation
.
isPermissionError :: IOError -> Bool Source
An error indicating that an IO
operation failed because the user does not have sufficient operating system privilege to perform that operation.
isUserError :: IOError -> Bool Source
A programmer-defined error value constructed using userError
.
ioeGetErrorType :: IOError -> IOErrorType Source
ioeGetLocation :: IOError -> String Source
ioeGetErrorString :: IOError -> String Source
ioeGetHandle :: IOError -> Maybe Handle Source
ioeGetFileName :: IOError -> Maybe FilePath Source
ioeSetErrorType :: IOError -> IOErrorType -> IOError Source
ioeSetErrorString :: IOError -> String -> IOError Source
ioeSetLocation :: IOError -> String -> IOError Source
ioeSetHandle :: IOError -> Handle -> IOError Source
ioeSetFileName :: IOError -> FilePath -> IOError Source
data IOErrorType Source
An abstract type that contains a value for each variant of IOError
.
Eq IOErrorType | Since: 4.1.0.0 |
Show IOErrorType | Since: 4.1.0.0 |
alreadyExistsErrorType :: IOErrorType Source
I/O error where the operation failed because one of its arguments already exists.
doesNotExistErrorType :: IOErrorType Source
I/O error where the operation failed because one of its arguments does not exist.
alreadyInUseErrorType :: IOErrorType Source
I/O error where the operation failed because one of its arguments is a single-use resource, which is already being used.
fullErrorType :: IOErrorType Source
I/O error where the operation failed because the device is full.
eofErrorType :: IOErrorType Source
I/O error where the operation failed because the end of file has been reached.
illegalOperationErrorType :: IOErrorType Source
I/O error where the operation is not possible.
permissionErrorType :: IOErrorType Source
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
userErrorType :: IOErrorType Source
I/O error that is programmer-defined.
IOErrorType
predicatesisAlreadyExistsErrorType :: IOErrorType -> Bool Source
I/O error where the operation failed because one of its arguments already exists.
isDoesNotExistErrorType :: IOErrorType -> Bool Source
I/O error where the operation failed because one of its arguments does not exist.
isAlreadyInUseErrorType :: IOErrorType -> Bool Source
I/O error where the operation failed because one of its arguments is a single-use resource, which is already being used.
isFullErrorType :: IOErrorType -> Bool Source
I/O error where the operation failed because the device is full.
isEOFErrorType :: IOErrorType -> Bool Source
I/O error where the operation failed because the end of file has been reached.
isIllegalOperationErrorType :: IOErrorType -> Bool Source
I/O error where the operation is not possible.
isPermissionErrorType :: IOErrorType -> Bool Source
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
isUserErrorType :: IOErrorType -> Bool Source
I/O error that is programmer-defined.
ioError :: IOError -> IO a Source
Raise an IOError
in the IO
monad.
catchIOError :: IO a -> (IOError -> IO a) -> IO a Source
The catchIOError
function establishes a handler that receives any IOError
raised in the action protected by catchIOError
. An IOError
is caught by the most recent handler established by one of the exception handling functions. These handlers are not selective: all IOError
s are caught. Exception propagation must be explicitly provided in a handler by re-raising any unwanted exceptions. For example, in
f = catchIOError g (\e -> if IO.isEOFError e then return [] else ioError e)
the function f
returns []
when an end-of-file exception (cf. isEOFError
) occurs in g
; otherwise, the exception is propagated to the next outer handler.
When an exception propagates outside the main program, the Haskell system prints the associated IOError
value and exits the program.
Non-I/O exceptions are not caught by this variant; to catch all exceptions, use catch
from Control.Exception.
Since: 4.4.0.0
tryIOError :: IO a -> IO (Either IOError a) Source
The construct tryIOError
comp
exposes IO errors which occur within a computation, and which are not fully handled.
Non-I/O exceptions are not caught by this variant; to catch all exceptions, use try
from Control.Exception.
Since: 4.4.0.0
modifyIOError :: (IOError -> IOError) -> IO a -> IO a Source
Catch any IOError
that occurs in the computation and throw a modified version.
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.2.1/docs/html/libraries/base-4.10.0.0/System-IO-Error.html