| Safe Haskell | Safe | 
|---|
System.IO.Error
Contents
- type IOError = IOError
- 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
- ioeGetErrorString :: IOError -> String
- ioeGetHandle :: IOError -> Maybe Handle
- ioeGetFileName :: IOError -> Maybe FilePath
- data IOErrorType
- alreadyExistsErrorType :: IOErrorType
- doesNotExistErrorType :: IOErrorType
- alreadyInUseErrorType :: IOErrorType
- fullErrorType :: IOErrorType
- eofErrorType :: IOErrorType
- illegalOperationErrorType :: IOErrorType
- permissionErrorType :: IOErrorType
- userErrorType :: IOErrorType
- ioError :: IOError -> IO a
- catch :: IO a -> (IOError -> IO a) -> IO a
- try :: IO a -> IO (Either IOError a)
I/O errors
Errors of type IOError are used by the IO monad.  This is an
 abstract type; the module System.IO.Error provides functions to
 interrogate and construct values of type IOError.
mkIOError :: IOErrorType -> String -> Maybe Handle -> Maybe FilePath -> IOErrorSource
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.
Classifying I/O errors
isAlreadyExistsError :: IOError -> BoolSource
An error indicating that an IO operation failed because
 one of its arguments already exists.
isDoesNotExistError :: IOError -> BoolSource
An error indicating that an IO operation failed because
 one of its arguments does not exist.
isAlreadyInUseError :: IOError -> BoolSource
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 -> BoolSource
An error indicating that an IO operation failed because
 the device is full.
isEOFError :: IOError -> BoolSource
An error indicating that an IO operation failed because
 the end of file has been reached.
isIllegalOperation :: IOError -> BoolSource
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 -> BoolSource
An error indicating that an IO operation failed because
 the user does not have sufficient operating system privilege
 to perform that operation.
isUserError :: IOError -> BoolSource
A programmer-defined error value constructed using userError.
Attributes of I/O errors
ioeGetHandle :: IOError -> Maybe HandleSource
Types of I/O error
data IOErrorType Source
An abstract type that contains a value for each variant of IOError.
Instances
alreadyExistsErrorType :: IOErrorTypeSource
I/O error where the operation failed because one of its arguments already exists.
doesNotExistErrorType :: IOErrorTypeSource
I/O error where the operation failed because one of its arguments does not exist.
alreadyInUseErrorType :: IOErrorTypeSource
I/O error where the operation failed because one of its arguments is a single-use resource, which is already being used.
fullErrorType :: IOErrorTypeSource
I/O error where the operation failed because the device is full.
eofErrorType :: IOErrorTypeSource
I/O error where the operation failed because the end of file has been reached.
illegalOperationErrorType :: IOErrorTypeSource
I/O error where the operation is not possible.
permissionErrorType :: IOErrorTypeSource
I/O error where the operation failed because the user does not have sufficient operating system privilege to perform that operation.
userErrorType :: IOErrorTypeSource
I/O error that is programmer-defined.
Throwing and catching I/O errors
catch :: IO a -> (IOError -> IO a) -> IO a
The catch function establishes a handler that receives any IOError
 raised in the action protected by catch.  An IOError is caught by
 the most recent handler established by catch.  These handlers are
 not selective: all IOErrors are caught.  Exception propagation
 must be explicitly provided in a handler by re-raising any unwanted
 exceptions.  For example, in
f = catch 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.