IOError package:base

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.

Raise an IOError in the IO monad.

An abstract type that contains a value for each variant of IOError.

Construct an IOError based on the given Errno value. The optional information can be used to improve the accuracy of error messages.

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.

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 IOErrors 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.

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.

Catch any IOError that occurs in the computation and throw a modified version.

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.