| Copyright | (c) The University of Glasgow 2001 |
|---|---|
| License | BSD-style (see the file libraries/base/LICENSE) |
| Maintainer | libraries@haskell.org |
| Stability | provisional |
| Portability | portable |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
System.IO.Error
Contents
Description
Standard IO Errors.
Synopsis
- type IOError = IOException
- userError :: String -> IOError
- mkIOError :: IOErrorType -> String -> Maybe Handle -> Maybe FilePath -> IOError
- annotateIOError :: IOError -> String -> Maybe Handle -> Maybe FilePath -> IOError
- isAlreadyExistsError :: IOError -> Bool
- isDoesNotExistError :: IOError -> Bool
- isAlreadyInUseError :: IOError -> Bool
- isFullError :: IOError -> Bool
- isEOFError :: IOError -> Bool
- isIllegalOperation :: IOError -> Bool
- isPermissionError :: IOError -> Bool
- isUserError :: IOError -> Bool
- ioeGetErrorType :: IOError -> IOErrorType
- ioeGetLocation :: IOError -> String
- ioeGetErrorString :: IOError -> String
- ioeGetHandle :: IOError -> Maybe Handle
- ioeGetFileName :: IOError -> Maybe FilePath
- ioeSetErrorType :: IOError -> IOErrorType -> IOError
- ioeSetErrorString :: IOError -> String -> IOError
- ioeSetLocation :: IOError -> String -> IOError
- ioeSetHandle :: IOError -> Handle -> IOError
- ioeSetFileName :: IOError -> FilePath -> IOError
- data IOErrorType
- alreadyExistsErrorType :: IOErrorType
- doesNotExistErrorType :: IOErrorType
- alreadyInUseErrorType :: IOErrorType
- fullErrorType :: IOErrorType
- eofErrorType :: IOErrorType
- illegalOperationErrorType :: IOErrorType
- permissionErrorType :: IOErrorType
- userErrorType :: IOErrorType
- isAlreadyExistsErrorType :: IOErrorType -> Bool
- isDoesNotExistErrorType :: IOErrorType -> Bool
- isAlreadyInUseErrorType :: IOErrorType -> Bool
- isFullErrorType :: IOErrorType -> Bool
- isEOFErrorType :: IOErrorType -> Bool
- isIllegalOperationErrorType :: IOErrorType -> Bool
- isPermissionErrorType :: IOErrorType -> Bool
- isUserErrorType :: IOErrorType -> Bool
- ioError :: IOError -> IO a
- catchIOError :: IO a -> (IOError -> IO a) -> IO a
- tryIOError :: IO a -> IO (Either IOError a)
- modifyIOError :: (IOError -> IOError) -> IO a -> IO a
I/O errors
type IOError = IOException #
The Haskell 2010 type for exceptions in the IO monad.
Any I/O operation may raise an IOException 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 #
Construct an IOException 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 #
Construct an IOException 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 #
Adds a location description and maybe a file path and file handle
to an IOException. If any of the file handle or file path is not given
the corresponding value in the IOException remains unaltered.
Classifying I/O errors
isAlreadyExistsError :: IOError -> Bool #
An error indicating that an IO operation failed because
one of its arguments already exists.
isDoesNotExistError :: IOError -> Bool #
An error indicating that an IO operation failed because
one of its arguments does not exist.
isAlreadyInUseError :: IOError -> Bool #
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 #
An error indicating that an IO operation failed because
the device is full.
isEOFError :: IOError -> Bool #
An error indicating that an IO operation failed because
the end of file has been reached.
isIllegalOperation :: IOError -> Bool #
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 #
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 #
A programmer-defined error value constructed using userError.
Attributes of I/O errors
ioeGetErrorType :: IOError -> IOErrorType #
ioeGetLocation :: IOError -> String #
ioeGetErrorString :: IOError -> String #
ioeGetHandle :: IOError -> Maybe Handle #
ioeGetFileName :: IOError -> Maybe FilePath #
ioeSetErrorType :: IOError -> IOErrorType -> IOError #
ioeSetErrorString :: IOError -> String -> IOError #
ioeSetLocation :: IOError -> String -> IOError #
ioeSetHandle :: IOError -> Handle -> IOError #
ioeSetFileName :: IOError -> FilePath -> IOError #
Types of I/O error
data IOErrorType #
An abstract type that contains a value for each variant of IOException.
Instances
| Eq IOErrorType # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception Methods (==) :: IOErrorType -> IOErrorType -> Bool Source # (/=) :: IOErrorType -> IOErrorType -> Bool Source # | |
| Show IOErrorType # | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception Methods showsPrec :: Int -> IOErrorType -> ShowS # show :: IOErrorType -> String # showList :: [IOErrorType] -> ShowS # | |
alreadyExistsErrorType :: IOErrorType #
I/O error where the operation failed because one of its arguments already exists.
doesNotExistErrorType :: IOErrorType #
I/O error where the operation failed because one of its arguments does not exist.
alreadyInUseErrorType :: IOErrorType #
I/O error where the operation failed because one of its arguments is a single-use resource, which is already being used.
fullErrorType :: IOErrorType #
I/O error where the operation failed because the device is full.
I/O error where the operation failed because the end of file has been reached.
illegalOperationErrorType :: IOErrorType #
I/O error where the operation is not possible.
permissionErrorType :: IOErrorType #
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
userErrorType :: IOErrorType #
I/O error that is programmer-defined.
IOErrorType predicates
isAlreadyExistsErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because one of its arguments already exists.
isDoesNotExistErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because one of its arguments does not exist.
isAlreadyInUseErrorType :: IOErrorType -> Bool #
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 #
I/O error where the operation failed because the device is full.
isEOFErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because the end of file has been reached.
isIllegalOperationErrorType :: IOErrorType -> Bool #
I/O error where the operation is not possible.
isPermissionErrorType :: IOErrorType -> Bool #
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
isUserErrorType :: IOErrorType -> Bool #
I/O error that is programmer-defined.
Throwing and catching I/O errors
catchIOError :: IO a -> (IOError -> IO a) -> IO a #
The catchIOError function establishes a handler that receives any
IOException raised in the action protected by catchIOError.
An IOException is caught by
the most recent handler established by one of the exception handling
functions. These handlers are
not selective: all IOExceptions 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 IOException 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: base-4.4.0.0
tryIOError :: IO a -> IO (Either IOError a) #
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: base-4.4.0.0
modifyIOError :: (IOError -> IOError) -> IO a -> IO a #
Catch any IOException that occurs in the computation and throw a
modified version.