I am using this application to capture, log, and graph out ethernet utilization information on a couple network devices at work. The application collects data at five minute intervals and prints out the result from each "run" to the logfile.

Initially I had it print out each run line (with data) to the console when I was building the tool (so I could watch it), but now I am using a logfile so that I can do weekly/monthly reports etc. The application creates a new logfile for each day at 8am and will continue to run till 5pm and then exit. Here is a snippet of log information:

Now when I go and look at the current logfile for the day, I notice that no data actually gets printed to the file until run #74 (always) for each device (all seperate scripts in seperate dir's, with different logfiles). It prints up to the same point on line #74 and then doesn't print the remaining log info until program exit.

It looks to me like its waiting until some kind of buffer reaches a certain point, then dumps it out, then continues without printing until my program exists. In my current program I am writing to the logs like this:

open(LOG, "+>$logFile") || die "Can't open logfile: ($!)\n";
print LOG "Begin data collection for $host - Runs: $numRuns\n";
for ($run = 1; $run <= $numRuns; $run++) {
    print LOG "Starting run $run\\$numRuns - ";
    snmpRun();
    unless ($run == $numRuns) { sleep("$pauseTime"); }
}

[download]

This prints out the first line of my logfile, then calls the snmpRun sub from the loop. Inside my sub is this bit of code:
sub snmpRun {
...
print LOG "In: $octetInUtil Out: $octetOutUtil Time: $time\n";
...
}

[download]

Is there another way to do this so that the data does get written to the file as it hits the print lines? This isn't a big deal, but I'm curious to know.

djw

In reply to Is there a way to control when output gets printed to a file? by djw

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