[Libevent-users] file io

[arthur zhang]

Thanks William, you tell me (and help me) a lot.

So looks I will output the trace to a socket port and create a receiver to
write it to disk.

Cheers,

Arthur

On 10/9/07, William Ahern <william at 25thandclement.com> wrote:
>
> On Tue, Oct 09, 2007 at 11:06:21AM -0400, arthur zhang wrote:
> > Hi All,
> >
> > As my understanding, with libevent, any io should be non_blocking, and
> here
> > comes my dumb q;-)
> >
> > I want log stuffs(trace) to a disk file in my comm callback, so I open a
> > file like below, but I didn't get any write event to call back. I am
> using
> > Ubuntu Dapper and my target system is Solaris 10.
>
> 1) You can't do non-blocking file I/O in Unix using the standard
> interfaces.
>    You need to use a horrible and poorly implemented interfaces like POSIX
>    Asynchronous I/O, which is impossible to use with libevent.
>
> 2) A file descriptor (to a realfile) will _always_ poll as ready for
> reading
>    or writing.  (The logic being, even though the disk might be slow, it's
>    still always available for I/O--the disk is one gigantic buffer.) Thus,
>    if your code was written properly your complaint should have been that
>    you got an endless succession of write readiness callbacks suspicously
>    lacking any gap.
>
> > Using stdout worked.
>
> If stdout was a pipe, then it would work. Thus, you could shamefully (but
> with good reason) pipe to cat, and redirect cat's stdout to a file.
>
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