I have a feeling this is not a "beginners" question (I've been hacking
in Perl for many years and UNIX systems for far longer) but it seems my
choices are this list, or perl5-porters which also doesn't seem right.
Isn't there any list where non-beginner questions can be asked?
Anyway.
I have a Perl environment which is v5.8.8 built for
x86_64-linux-thread-multi, running on a Red Hat Enterprise Linux 5.3
system. In this environment, I create a pipe then I want to know the
maximum amount I can write to the pipe without blocking. So, I have
this code:
my ($printrd, $printwd, $pipebuf);
pipe($printrd, $printwd) or die "pipe(print): $!\n";
$pipebuf = fpathconf($printwd, _PC_PIPE_BUF)
or die "fpathconf(pipe): $!\n";
I wrote this code in 2007 and it's run on Red Hat EL 4 and EL 5 systems
for years. Once or twice over that time I got reports, that were never
reproduced, of the latter die (fpathconf) being hit. The error was
"invalid file descriptor".
Within the last month or so (I have NO IDEA what's changed!) I've
started getting failures (on multiple quite different systems)
irregularly still, but much more frequently.
I'm really stumped as to what might be the problem here.
Playing around I changed the code so that if the fpathconf() of the
write FD failed, it would try the read FD. I can't be sure (since the
problem is intermittent) but is _seems_ like the read FD is working.
I really don't want to just change this and call it good, though,
without some indication that this is really the problem, and it's not
just that I've been lucky so far with the read FD.
Has anyone ever heard of anything like this before? Is it true that
it's better/safer (in Perl? Everywhere?) to run fpathconf() on the read
FD? I've never heard of such a thing, but if this is a known behavior
that's fine with me.
Thanks...
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