Make a nice buffer?

List,
I want to make a buffer for my application to write log data to.  I've
created a fifo (`mkfifo /tmp/buf`)  Then I made my PERL script that
reads from /tmp/buf.  Other programs open and write to /tmp/buf but when
they close then my program that is reading from /tmp/buf stops.  I want
the script that reads and buffers (then parses and other such stuff) not
to close when the other folks are done writing to the fifo at /tmp/buf.
Ideas?  Should I just loop and re-open after every close (seems bad).

/djb

On Thursday 25 March 2004 10:30 pm, David Busby wrote:
> List,
>   I want to make a buffer for my application to write log data to.  I've
> created a fifo (`mkfifo /tmp/buf`)  Then I made my PERL script that
> reads from /tmp/buf.  Other programs open and write to /tmp/buf but when
> they close then my program that is reading from /tmp/buf stops.  I want
> the script that reads and buffers (then parses and other such stuff) not
> to close when the other folks are done writing to the fifo at /tmp/buf.
> Ideas?  Should I just loop and re-open after every close (seems bad).
>
> /djb

Hi David,

I think that's the normal for pipes.  The way I understand it, a pipe is
simply a meeting point for someone openening a file for writing and one
opening a file for reading.  If you open first, your open won't complete
until the other proces tries to open soon.  Then their write open is directl
y
connected to your read open.  This means that when they close, you're closed
too.  As you can see from my code below, you have to re-open every time you
enter the loop.

Gary

#!/usr/bin/perl -w

my $VERSION='1.0.0';
# daemon to sit listening to a pipe and actioning print requests.
select(STDERR); $|=1;
select(STDOUT); $|=1;

my $inp;

chdir $ENV{RWDDATA} || die "cannot cd: $!\n";
die "pipe is missing\n" unless ( -p "rwfifo");

while (1) {
print "opening...";
open(FIN,"rwfifo") || die "cannot open pipe: $!";
print "Done\nreading pipe...";
$_=<FIN>;
chomp;
print "Done\n";
last if (/^quit/i);
next if (/loop/i);
print "executing rwlpr $_ loop .....";
print ((system "rwlpr $_ loop") ? "failed: $?\n" : "done\n");
print "reading pipe...";
}


--
Gary Stainburn

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