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From: allbery@NCoast.ORG (Brandon S. Allbery KB8JRR/KT)
Newsgroups: comp.lang.perl
Subject: Re: (f)flush?
Message-ID: <1990Aug4.191307.10807@NCoast.ORG>
Date: 4 Aug 90 19:13:07 GMT
References: <8936@jpl-devvax.JPL.NASA.GOV> <1990Aug2.225410.2587@NCoast.ORG> <8992@jpl-devvax.JPL.NASA.GOV>
Reply-To: allbery@ncoast.ORG (Brandon S. Allbery KB8JRR/KT)
Followup-To: comp.lang.perl
Organization: North Coast Public Access *NIX, Cleveland, OH
Lines: 43

As quoted from <8992@jpl-devvax.JPL.NASA.GOV> by lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall):
+---------------
| out in the I/O structure--look at IOF_FLUSH in stab.h.  When you refer to
| the $| varialbe, it's referring to that flag for the currently selected
| output filehandle, and not to the flag for any other filehandle.
+---------------

Eek.  I don't select filehandles, I refer to them explicitly.  Oh, well.

+---------------
| Depends on your implementation of STDIO, and what kind of thing you're writing
| to.  Turning off $| merely makes it not do flushes.  If it was unbuffered
| before, having $| on doesn't help you, and if it was buffered before, turning
| $| off won't make stdio unbuffered.  On most systems, output to (raw) tape and
| disks is buffered.
+---------------

But stdio buffers at something between 512 bytes and 8K by default, depending
on the implementation.  On the machines I use, it's 1K; that's a far cry from
512K blocks on a tape drive....

+---------------
| $| is not a global, and it has nothing to do with setbuf.
+---------------

I should have said setvbuf; I want user-specified block sizes, not just
stdio's fixed block size.  And stdio buffered output has to do with setvbuf,
and $| controls buffering.  (Although, from how you described $|, it's not
particularly useful for this purpose.)

+---------------
| On machines with syscall(), you can get around dumb stdio limitations using
| it.  It might be worthwhile for me to add a sysread() and syswrite()
| builtin to bypass stdio.
+---------------

SVR3.1, at least, doesn't have syscall.  I don't think 3.2 has it, either.

++Brandon
-- 
Me: Brandon S. Allbery			    VHF: KB8JRR/KT on 220 (soon others)
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