Some perl code based on dirwatcher.pl. This is my attempt to daemonize the code.

The program should run as a daemon and watch or poll a directory. The creation of new files should get logged to a file.

The program launches fine. I can touch a file in the watched directory but I see nothing in the log file until I kill the program. Once the program is killed, the LOG file is populated with desired log messages.

There must be a better way to do this without the traditional file handles. I guess killing the program closes the file-handle and flushes the buffer. The thread http://www.perlmonks.org/?node_id=557981 was very similar to my issue.

Any help, tips or pointers to docs appreciated.

#!/usr/bin/perl
#
#     Monitors a directory for file changes.
#
###
#
#     Default directory to be monitored.
#
my $directory = "/tmp/";
my $sleeptime = 3;

use POSIX qw(ceil floor);
use File::Basename;
use Proc::Daemon;

Proc::Daemon::Init;

my $continue = 1;

$SIG{TERM} = sub { $continue = 0 };

#     Directory on command-line
if ($#ARGV >= 0) { $directory = join(' ', @ARGV); }

#     Directories need to have a trailing slash
if (substr($directory,-1) ne "/") { $directory .= "/"; }

#     Check if the directory exists
if (!-e $directory) {
    print STDERR "'$directory' does not exist.\n";
    exit(-1);
}
#
#     Store file info here
#
my %data;
#
#     individual file statistics placed in this global array
#
my @gstat;
#
#     begin
#
$| = 1;
open LOG, ">>", "/var/tmp/foo.log";
print LOG "\nMonitoring directory: ".$directory."\n";

#
#     loop forever
#
while ($continue) {
    my $first = 0;
    #
    #     Get directory handle
    #
    opendir(DIR, $directory) 
        or die "Unable to open directory, $directory : $!";
    #
    #     And loop through the contents
    #
    while (defined(my $filename = readdir(DIR))) {
        #
        #     We only want files, not sub-directories
        #
        if (-d $directory.$filename) { next; }
        #
        #     Get inode statistics
        #
        @gstat = &getstat($filename);
        #
        #     If this is the first time it is being run, 
        #    don't want to spam that every file is new, 
        #    just add it to the hash
        #
        if (!scalar(%data)) { $first = 1; &update($filename); }
        # subsequent files are added on first run
        elsif ($first == 1) { &update($filename); }
        #
        #     Not first run, and new file found
        #
        elsif (!scalar($data{$filename})) { 
            my $ext = ($filename =~ m/([^.]+)$/)[0];
            my $retval = &doPrint($filename, 
                "Created. [".&printBytes($gstat[7])."]"); 
            print LOG $time." : $ext\n";
            &update($filename); 
        }
        #
        #     The size has changed
        #
        elsif ($data{$filename}{'size'} != $gstat[7]) {
            my $increase = $gstat[7] - $data{$filename}{'size'};
            my $text = "Size changed to ".&printBytes($gstat[7]);
            if ($increase > 0) { 
                $text .= " (up ".&printBytes($increase).")"; }
            elsif ($increase < 0) { 
             $text .= " (down ".&printBytes($increase * -1).")"; }
            &doPrint($filename, $text);
            &update($filename);
        }
        #
        #     The modified time has changed
        #    TODO - we should handle duplicate files is some
        #    logical way
        #
        elsif ($data{$filename}{'mtime'} != $gstat[9]) {
            &doPrint($filename, "Modified, size unchanged");
            &update($filename);
        }
    }
    #
    #     Clean up the directory handle
    #
    closedir(DIR);
    #
    #     Check for files in the hash which are no longer 
    #    in the directory
    #
    foreach $key (keys %data) {
        if (! -e $directory.$key) {
            &doPrint($key, "Deleted. Last modified at ".
                readTime($data{$key}{'mtime'})." (".
                &duration(time() - $data{$key}{'mtime'}).") [".
                &printBytes($data{$key}{'size'})."]");
            delete($data{$key});
        }
    }
    #
    #     Sleep for a bit, else it eats up the CPU
    #
    sleep($sleeptime);
}

#
#     returns the time in the format 
#    <year><month><day>.<hour><minute><second> .. 
#    hardly readable but concise
#
sub readTime {
    my ($second, $minute, $hour, $dayOfMonth, $month, 
        $yearOffset, $dayOfWeek, $dayOfYear, 
        $daylightSavings) = localtime(shift(@_));
    my $time = (1900+ $yearOffset).sprintf("%02d", $month).
        sprintf("%02d", $dayOfMonth).".".
        sprintf("%02d", $hour).sprintf("%02d", $minute).
        sprintf("%02d", $second);
    return $time;
}
#
#     Print out a file change in a consistent format
#
sub doPrint {
    my $fn = shift(@_);
    my $t = shift(@_);
    my $time = readTime(time());
    print LOG $time." : ".$fn."\t".$ext."\t".$t."\n";
}
#
#     Takes bytes are returns kilobytes, megabytes, 
#    gigabyte values instead based on set limits
#
sub printBytes {
    my $bytes = shift(@_);
    if ($bytes <= 4096) { return $bytes."b"; }
    $bytes = sprintf("%.2f",$bytes / 1024);
    if ($bytes <= 1024) { return $bytes."k"; }
    $bytes = sprintf("%.2f",$bytes / 1024);
    if ($bytes <= 1024) { return $bytes."m"; }
    $bytes = sprintf("%.2f",$bytes / 1024);
    return $bytes."g";
}

#
#     Take number of seconds and return duration, ie. 2d 4h 5m 14s
#
sub duration {
    my $time = shift(@_);
    if ($time == 0) { return "just now"; }
    my $string = "";
    my $days = floor($time / 86400); $time = $time - ($days * 86400);
    if ($days > 0) { $string .= $days."d "; }
    my $hours = floor($time / 3600); $time = $time - ($hours * 3600);
    if ($hours > 0) { $string .= $hours."h "; }
    my $mins = floor($time / 60); $time = $time - ($mins * 60);
    if ($mins > 0) { $string .= $mins."m "; }
    my $secs = $time;
    if ($secs > 0) { $string .= $secs."s "; }
    $string .= "ago";
    return $string;
}
#
#     Populate array with inode statistics
#
sub getstat {
    my $fn = $_[0];
    open(FILE, $directory.$fn);
    my @stat = stat(FILE);
    close(FILE);
    return @stat;
}
#
#     update the hash with file info
#
sub update {
    my $fn = $_[0];
    $data{$fn} = {
        size => $gstat[7],
        mtime => $gstat[9],
    };
}
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