| Gary Stainburn 2004-03-26, 11:15 pm |
| 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 directly
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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