O_DIRECT, core_unix, Open_flags, direct

[tomjridge]

I was looking for a way of opening a file using the O_DIRECT flag. I saw that core_unix has a module Open_flags which includes O_DIRECT. This looks great. However, there appears to be no way to actually open a file with that flag (I think Open_flags are currently only used with fcntl). Is there any way to open a file with the O_DIRECT flag? Do you intend to add this functionality at some point? Do you know any libraries that currently support this flag? Thanks

[bcc32]

The O_DIRECT flag isn't supported by Unix.openfile because there's currently two types, Unix.open_flag (which is an alias to the one from the OCaml stdlib) and Open_flags.t, which includes O_DIRECT. Making Unix.openfile support the latter would probably be a decently big change.

As a workaround, could you use fcntl_setfl to set Open_flags.direct on the file descriptor after opening it? I realize the documentation may be a bit out of date on that function, as man fcntl says Linux supports setting O_DIRECT there.