I have written a script to look for a specific string occurring within a log on a windows system. The log fills up very quickly and therefore rolls over (rotates) often. For some reason though, while my script is running, the file will not roll-over, presumably because the rolling mechanism cannot get a suitable lock on the file. I have tried using File::Tail and POE::Wheel::FollowTail and both work fine except for not allowing the file to roll-over.

As an experiment, I have tried using SFU's "tail -f" and that doesn't keep the rollover from occurring, but of course also doesn't follow the new file when a roll-over does occur.

I can think of several ways to periodically release and re-open the file, but it is too easy to miss an occurrance of the issue that way.

I will paste the applicable code from both methods I have tried below.

Any enlightenment would be greatly appreciated,
-Frd

File::Tail code: 

    my $file=File::Tail->new(name=>"$SEARCH_LOG", maxinterval=>10);
    LogIt("Initiated 'tail' ... reading file '$SEARCH_LOG':\n");
    LogIt("    ... Looking for '$STRING'\n");

    while (defined(my $line=$file->read)) {
        LogIt("Read line: $line");
        next unless ( $line =~ /$STRING/ );
        LogIt("That Line MATCHES SEARCH STRING: '$STRING'\n");
        lock($occurred);
        $occurred ++;
        LogIt("$line");
        LogIt("Increasing OCCURRED flag to '$occurred'");
    }

[download]

POE code: 

POE::Session->create(
    inline_states => {
        _start => sub {
            $_[HEAP]{tailor} = POE::Wheel::FollowTail->new(
                Filename   => "$SEARCH_LOG",
                InputEvent => "got_log_line",
                ResetEvent => "got_log_rollover",
            );
        },
        got_log_line => sub {
            my $line = $_[ARG0];
            LogIt("Read line: $line");
            return unless ( $line =~ /$STRING/ );
            LogIt("That Line MATCHES SEARCH STRING: '$STRING'\n");
            lock($occurred);
            $occurred++;
            LogIt("$line");
            LogIt("Increasing OCCURRED flag to '$occurred'");
        },
        got_log_rollover => sub {
            LogIt("Log rolled over.\n");
        },
    }
);

[download]

In reply to Tail'ing a log that frequently rolls over by frd1963

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