It’s “Oh crap! I haven’t posted anything useful in a long time” time! So, I’ll take a little snip from one of those quick hack programs I wrote that evolved into a test verification tool (sigh).

This function creates a basic histogram from values passed in an array. It is specifically set up to take timestamps, group them by hour, and print a histogram next to the values:”

    # Prints messages sent by wall clock hour
    sub hourlyDistribution {
        my @rawtimes = shift;
        my %time_distrib;
        my $factor = 1;
        my $maxlen = 0;
        my $wchar = screenwidth();

        foreach (@rawtimes) {

            #this works, but in my case the times are in GMT
            #my $bucket = int ($_ / (60 * 60)) % 24;
            # this does the distribution in local time
            my $bucket = (localtime($_))[2];

            $time_distrib{$bucket}++;
            $maxlen = $time_distrib{$bucket}
            unless $maxlen >= $time_distrib{$bucket};
        }

        # ok the 16 is a totally hardcoded "this much room for stuff before the histogram"
        # but the rest of the logic is solid, if there are more elements than the screen can
        # hold, create a scaling $factor so the graph will fit. Not very granular, uses integer
        # math, but hey, we're printing asterisks.
        if ( ( $wchar - 16 ) < $maxlen ) {
            $factor = $maxlen / ( $wchar - 16 );
        }

        print
        "\nHour\tCount\tGraph\n";
        print "----\t-----\t-----\n";
        foreach ( sort { $a  $b } keys %time_distrib ) {
            print "$_\t$time_distrib{$_}\t"
            . '*' x ( $time_distrib{$_} / $factor )
            . "\n";
        }
    }

So, screenwidth gets, wait for it, the screen width in columns.

    # Set a var if we can't load Term::Readkey
    # Helpful on a server you can't load modules on to.
    my $noreadkey    = 0;
    eval "use Term::ReadKey; 1" or $noreadkey = 1;

    sub screenwidth () {
        my ( $wchar, $hchar, $wpixels, $hpixels );
        if ( $noreadkey ) {
            #hardwidth gets set to your default. 40, 80, whatever.
            return $hardwidth;
        } else {
            # Yes, you could just return (GetTerminalSize())[0]
            # But then it would be all mysterious.
            ( $wchar, $hchar, $wpixels, $hpixels ) = GetTerminalSize();
            return $wchar;
        }

    }