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Where are the other open flags #6
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The design is kind of gross there, I would have newtyped over the int and provided a Monoid instance. That said we're probably stuck with it now. Please send a pull request if you need the other flags (it will require a major version bump).
I cannot say much about the other flags, but
O_CLOEXECis important because it is the only way you are guaranteed in the general case not to leak FDs in a multi-threaded program that forks.@gregorycollins If I want to add some things to this, how would I deal with cross-platform compatibility and what platforms to I have to take care of?
Relatedly, this is the intersection of supported
O_*flags for Linux and BSD:O_APPEND O_CLOEXEC O_CREAT O_DIRECT O_DIRECTORY O_EXCL O_NOCTTY O_NOFOLLOW O_NONBLOCK O_SYNC O_TRUNCAnd of those, the following are not implemented in the
unixpackage:O_CLOEXEC O_CREAT O_DIRECT O_DIRECTORY O_NOFOLLOW O_SYNCAlso,
O_CLOEXECdoesn't seem to be supported on OSX < 10.7, see this Go thread.is there any reason why the alternative monoidal interface couldn't be added?
add a new module? :)
something likeSystem.Posix.IO.NGor something?...or just by adding a new open function with a new name.
I think we should deprecate the old style --- as noted on this bug, it doesn't cover all of the available flags, and extending the type or providing platform-specific flags is problematic because you will break pattern-matching if callers do that for some reason. The current API is also wasteful -- six heap allocations and all of those bools have to be walked by openFd. Newtype-over-int will probably get unboxed into a register.
thats a better idea :)
- added a commit that references this issue
on Feb 23, 2018 @gregorycollins If I want to add some things to this, how would I deal with cross-platform compatibility and what platforms to I have to take care of?
Relatedly, this is the intersection of supported
O_*flags for Linux and BSD:O_APPEND O_CLOEXEC O_CREAT O_DIRECT O_DIRECTORY O_EXCL O_NOCTTY O_NOFOLLOW O_NONBLOCK O_SYNC O_TRUNCAnd of those, the following are not implemented in the
unixpackage:O_CLOEXEC O_CREAT O_DIRECT O_DIRECTORY O_NOFOLLOW O_SYNCunix-2.8.0.0 will have:
data OpenFileFlags = OpenFileFlags { append :: Bool, -- ^ O_APPEND exclusive :: Bool, -- ^ O_EXCL, result is undefined if O_CREAT is False -- -- __NOTE__: Result is undefined if 'creat' is 'Nothing'. noctty :: Bool, -- ^ O_NOCTTY nonBlock :: Bool, -- ^ O_NONBLOCK trunc :: Bool, -- ^ O_TRUNC nofollow :: Bool, -- ^ O_NOFOLLOW -- -- @since 2.8.0.0 creat :: Maybe FileMode, -- ^ O_CREAT -- -- @since 2.8.0.0 cloexec :: Bool, -- ^ O_CLOEXEC -- -- @since 2.8.0.0 directory :: Bool, -- ^ O_DIRECTORY -- -- @since 2.8.0.0 sync :: Bool -- ^ O_SYNC -- -- @since 2.8.0.0 }
O_DIRECTdoesn't seem to be part of POSIX: https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/So I think this can be closed.
@hasufell Thank you, that is very useful.
I am very looking forward to the unix-2.8.0.0 release; with #59 in there we will finally have a chance to tack The CLOEXEC problem across the Haskell ecosystem.
Also thanks for your other recent
unixefforts!
I'd like to create an FD with
O_CLOEXEC.What would be the most high-level way to do that?
http://hackage.haskell.org/package/unix-2.7.0.1/docs/System-Posix-IO.html#v:OpenFileFlags only gives me
append,exclusive,noctty,nonBlock,trunc. What's the idea behind this selection, and can the other flags easily be added?