Checks Reddit for new posts to /r/buildapcsales matching a specified tag, sends email when it finds something new. Depends on XML::RSS::Parser and the Linux 'mail' command (tested with mailx)

pricemonitor.pl

#!/usr/bin/perl
use strict;
use IO::File;
use Date::Parse;
use XML::RSS::Parser;

my $tag = "GPU";

my $time_file = "/home/username/pricemonitor_lasttime.txt";

# Email source and destination
my $src_addr = "source@example.com";
my $dst_addr = "destination@example.com";

# Download RSS Feed
my $url = "https://www.reddit.com/r/buildapcsales/new.rss";
my $xml = qx{curl --silent $url};
die "Couldn't get data from reddit!" unless defined $xml;

# Parse the XML
my $rp = XML::RSS::Parser->new;
my $feed = $rp->parse_string($xml);

# Check program last run time
open(TIMEFH, "<$time_file");
my $last_time = <TIMEFH>;
close (TIMEFH);
if (!defined $last_time) {
    $last_time = 0;
}
# Keep track of the greatest deal time seen
my $greatest_time = $last_time;

# Loop through results
foreach my $i ($feed->query('//item')) {
    my $title   = $i->query('title')->text_content;
    my $url     = $i->query('link')->text_content;
    my $date    = $i->query('pubDate')->text_content;
    my $unix    = str2time($date);

    #print $title . " " . $url . "\n";

    # Check if title matches tag
    if ($title =~ /\[.*$tag.*\]/i) {
        # Check if this is new since last run
        if ($unix > $last_time) {
            qx{echo -n '$title $url' | mail -r "$src_addr" $dst_addr};
            if ($unix > $greatest_time) {
                $greatest_time = $unix;
            }
        }
    }
}

# Set program last run time (write to file)
open(TIMEFH, ">$time_file") or die "Couldn't open $time_file for write!";
print TIMEFH "$greatest_time";
close(TIMEFH);