Unix/Posix-specific functions for ByteStrings.


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BSD-3-Clause licensed by wren gayle romano
Maintained by [email protected]
This version can be pinned in stack with:unix-bytestring-,3166

Module documentation for

Depends on 2 packages(full list with versions):


Hackage version Build Status Dependencies

Unix/Posix-specific functions for ByteStrings.

This package provides ByteString file-descriptor based I/O API, designed loosely after the String file-descriptor based I/O API in System.Posix.IO. The functions here wrap standard C implementations of the functions specified by the ISO/IEC 9945-1:1990 (“POSIX.1”) and X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”) specifications.

Note that this package doesn’t require the unix package as a dependency. But you’ll need it in order to get your hands on an Fd, so we’re not offering a complete replacement.


In general, this is a simple package and should be easy to install. You must have hsc2hs installed in order to compile the package (but then you probably already do). With the cabal-install program you can just do the standard:

$> cabal install unix-bytestring

FFI Problems

The unix-bytestring package uses standard POSIX header files <sys/types.h>, <sys/uio.h>, and <unistd.h>. If Cabal has difficulty finding these files or reports another error, be sure your include path variables are correct. If the problem persists, contact the maintainer.

Building for GHC (6.8 and above)

Nothing special to mention.

Building for Hugs (September 2006)

I haven’t actually compiled this for Hugs because I don’t have a new enough version of Cabal for it, but I don’t forsee any difficulties. If you do compile this for Hugs, let the maintainer know how it went.

When compiling for Hugs, see the following bugs for Cabal’s interaction with ffihugs. These bugs do not currently affect this package, but this notice is here in case they affect future versions. For more details and a minimal regression suite, see:


(1) http://hackage.haskell.org/trac/hackage/ticket/526 Options in hugs-options aren’t passed through to ffihugs, most importantly -98 and +o are the ones we’d like to pass. For enabling the +o flag Hugs-Sept06 does not honor: pragma {-# LANGUAGE OverlappingInstances #-} pragma {-# OPTIONS_HUGS +o #-} cabal extensions: OverlappingInstances And the -98 flag has similar issues. Therefore this is a real problem.

Immediate solution: The options set in hugs-options should be passed to ffihugs as well. As of Cabal 1.6 they are not passed (verified by Duncan Coutts). The two programs accept all the same options, so this is valid.

Ideal solution: Based on the extensions field, Cabal should automatically determine whether -98 and +o need to be enabled (for both hugs and ffihugs).

(2) http://hackage.haskell.org/trac/hackage/ticket/527 If CPP is being used in conjunction with FFI, then cpp/cpphs is not called before ffihugs is called. Thus, users must pass an -F flag to ffihugs in order to declare a code filter (and must pass all cpp-options to -F manually). For example:

--ffihugs-option=-F'cpp -P -traditional -D__HUGS__ -D__BLAH__'

This requires duplicating the build specifications, which defeats the point of Cabal. Also it leads to tricky issues about ensuring the proper level of quoting/escaping. (e.g. using the plural, –ffihugs-options=…, breaks it. Wrapping the -F’cpp…’ in double quotes breaks it.)