Dear Wise Monks,

I have been playing around with reading a FIFO that was created like so: 

$ sudo mkfifo /var/log/blackhole.pipe

[download]
Then I modified my /etc/syslog.conf ... 
$ cat /etc/syslog.conf 
...
# test logger script
local1.*      |/var/log/blackhole.pipe

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... then restart syslogd. I can test like by executing ... 
$ logger -p local1.info "test test"
$ logger -p local1.info "test test"
$ logger -p local1.info "test test"
$ logger -p local1.info "test test2"

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.. and ... 
$ cat /var/log/blackhole.pipe
Oct  3 11:16:09 localhost plankton: test test
Oct  3 11:16:15 localhost last message repeated 2 times
Oct  3 11:16:19 localhost plankton: test test2

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... but when I run this scripts ... 
$ cat process_blackhole.pl 
#!/usr/bin/perl -w

use strict;
$|=1;
my $fifo_file = "/var/log/blackhole.pipe";

my $fifo_fh;
open($fifo_fh, "+< $fifo_file") or die "The FIFO file \"$fifo_file\" i
+s missing, and this program can't run without it.:$!";

# just keep reading from the fifo and processing the events we read
while (<$fifo_fh>) {
        chomp;
        print "read from pipe [$_]\n";
}

# should never really come down here ...
close $fifo_fh;
exit(0);

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... I get this output ... 
$ sudo ./process_blackhole.pl 
read from pipe [Oct  3 11:22:45 localhost plankton: test test]
read from pipe [Oct  3 11:22:52 localhost plankton: test test2]

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... The strange thing is I do not always get the last message repeated 4 times output consistently. Is there something else besides $|=1 and using the +< on my open call ?

In reply to Understanding FIFO pipes and Syslog by Plankton

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