DNS Linux Network Technologies Perl

Announcing a simple DNS web interface and code

For demonstration purposes I’ve written a WEB interface to do DNS queries. This can be used for light querying. Once it gets abused I will pull it from the web site.

Some large enterprises are behind not only a corporate firewall, but also confined to a private namespace with no access to Internet name resolution. Users in such situations can use one of the many available tools to do DNS resolution through the web, but they all want to throw advertising at you and it’s not clear which can be trusted not to load you up with spyware. I am offering this ad-free DNS lookup using my position on the Internet as a trusted source.

And if you’re lucky and looking for code to do this yourself, you might find it. But nowhere will you find a site that’s running its own published code for DNS resolution. Except here.

The code
Admittedly very simple-minded, but hopefully not fatally flawed, here it is in Perl.

use CGI;
$query = new CGI;
%allowedArgs = (domainname => 'dum',type => 'dum',short => 'dum');
print "Content-type: text/html\n\n";
print "
foreach $key ($query->param) {
  exit(1) unless defined $allowedArgs{$key};
  exit(1) if $query->param($key) !~ /^([a-zA-Z0-9\.-]){2,256}$/;
  print "$key " . $query->param($key) . "\n";
# possible keys: domainname, type
$domainname = $query->param(domainname);
$type     = $query->param(type);
$type = "any" unless $type;
# argument validation checks
exit(1) if $domainname !~ /^([a-zA-Z0-9\.-]){2,256}$/ || $domainname =~ /\.\./ ||  ! $domainname;
exit(1) if $type !~ /^([a-zA-Z]){1,8}$/;

# short answer?
$short = "+short" if defined $query->param(short);

# authoritative request?
if (defined $query->param(authoritative)) {
# this will be a lot more complicated and so is not implemented. Perhaps someday if there is a request...

open(DIG,"dig $short $type $domainname|") || die "Cannot run dig!!\n";
while() {
  print ;

Yes it’s very old-school. I do not even use a DNS package. Why bother? It’s not rocket science. There’s a lot more to argument validation than it looks like – you would not believe the evil things people send to your web server. So you have to vigilant about injection attacks or shelling out by use of unexpected characters.


2020 Update

This URL has been deactivated since I moved to my new server. I’ll have to see if there’s time and interest to restore this functionality.

example 1

type a
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6_4.4 <<>> a
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8711
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;		IN	A
;; Query time: 10 msec
;; WHEN: Mon May  4 14:59:05 2015
;; MSG SIZE  rcvd: 51

example 2


Familiarity with dig will help you determine the best switches to use as you can see that at the end of the day it is merely calling dig and sending back that output with a minimum of html markup. This will make it easy to parse the output programatically.

A simple DNS web interface is being announced today. Both the service and the code are being made available. The service may be pulled once it becomes abused.

A nice, not too commercial web interface to dig and traceroute that is more user-friendly than mine is
The dig man pages can be helpful.

Got a geoDNS entry? Although this link has ads, it’s quite interesting because it sends your query to open DNS servers around the world:

You can explore some details behind Google’s public resolving server by using the web site: It’s quite helpful.

I won’t paste the link to my service but you can see what it is from the examples above.

There’s a simple but effective DIG available for your Android smartphone from the Playstore. That’s DNS debugger from TurboBytes. No obnoxious ads and yet no cost.

Of course if you are on the Internet and have access to dig, Google’s DNS servers are available for you to use directly.

Want to learn if the Great Friewall of China is clobbering the expected DNS result? The site is designed to do just that.

Internet Mail Linux Perl Raspberry Pi

Raspberry Pi phone home

In this article I described setting up my Raspberry Pi without ever connecting a monitor keyboard and mouse to it and how I got really good performance using an UHS SD card.

This article represents my first real DIY project on my Pi – one of my own design. My faithful subscribers will recall my post after Hurricane Sandy in which I reacted to an intense desire to know when the power was back on by creating a monitor for that situation. It relied on extremely unlikely pieces of infrastructure. I hinted that it may be possible to use the Raspberry Pi to accomplish the same thing.

I’ve given it a lot of thought and assembled all the pieces. Now I have a home power/Internet service monitor based on my Pi!

This still requires a somewhat unlikely but not impossible combination of infrastructure:
– your own hosted server in the cloud
– ability to send emails out from your cloud server
– access log files on your cloud server are rolled over regularly
– your Pi and your cloud server are in the same time zone
– Raspberry Pi which is acting as a server (meaning you are running it 24×7 and not rebooting it and fooling with it too much)
– a smart phone to receive alert emails or TXT messages

I used my old-school knowledge of Perl to whip something up quickly. One of this years I have to bite the bullet and learn Python decently, but it’s hard when you are so comfortable in another language.

The details
Here’s the concept. From your Pi you make regular “phone home” calls to your cloud server. This could use any protocol your server is listening on, but since most cloud servers run web servers, including mine, I phone home using HTTP. Then on your cloud server you look for the phone home messages. If you don’t see one after a certain time, you send an alert to an email account. Then, once service – be it power or Internet connectivity – is restored to your house, your Pi resumes phoning home and your cloud monitor detects this and sends a Good message.

I have tried to write minimalist code that yet will work and even handle common error conditions, so I think it is fairly robust.

Set up your Pi
On your Pi you are “phoning home” to your server. So you need a line something like this in your crontab file:

# This gets a file and leaves a timestamp behind in the access log
* * * * * /usr/bin/curl --connect-timeout 30`perl -e 'print time()'` > /dev/null 2>&1

Don’t know what I’m talking about when I say edit your crontab file?

> export EDITOR=vi
> crontab -e

That first line is only required for fans of the vi editor.

That part was easy, right? That will have your server “phone home” every minute, 24×7. But we need an aside to talk about time on the Pi.

Getting the right time on the Raspberry Pi
This monitoring solution assumes Ras Pi and home server are in the same time zone (because we kept it simple). I’ve seen at least a couple of my Raspberry Pi’s where the time zone was messed up so I need to document the fix.

Run the date command
$ date

Sat Apr 29 17:10:13 EDT 2017

Now it shows it is set for EDT so the timezone is correct. At first it showed something like UTC.

Make sure you are running ntp:
$ ntpq ‐p

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================     2 u  689 1024  377   78.380    2.301   0.853     2 u  312 1024  377  116.254   11.565   5.864
+choppa.chieftek     3 u  909 1024  377   65.430    4.185   0.686
*   .GPS.            1 u  106 1024  377  162.089  -10.357   0.459

You should get results similar to those above. In particular the jitter numbers should be small, or at least less than 10 (units are msec for the curious).

If you’re missing the ntpq command then do a

$ sudo apt-get install ntp

Set the correct timezone with a

$ sudo dpkg-reconfigure tzdata

and choose Americas, then new York, or whatever is appropriate for your geography. The Internet has a lot of silly advice on this point so I hope this clarifies the point.

Note that you need to do both things. In my experience time on Raspberry Pis tends to drift so you’ll be off by seconds, which is a bad thing. ntp addresses that. And having it in the wrong timezone is just annoying in general as all your logs and file times etc will be off compared to how you expect to see them.

On your server
Here is the Perl script I cooked up. Some modifications are needed for others to use, such as email addresses, access log location and perhaps the name and switches for the mail client.

So without further ado. here is the monitor script:

# send out alerts related to Raspberry Pi phone home
# this is designed to be called periodically from cron
# DrJ - 2/2013
# to test good to error transition,
# call with a very small maxDiff, such as 0!
use Getopt::Std;
getopts('m:d'); # maximum allowed time difference
$maxDiff = $opt_m;
$DEBUG = 1 if $opt_d;
unless (defined($maxDiff)) {
# use values appropriate for your situation here...
$mailsender = '[email protected]';
$recipient = '[email protected]';
$monitorName = 'Raspberry Pi phone home';
# access line looks like:
# - - [02/Feb/2013:22:00:02 -0500] "GET /raspberrypiPhoneHome?136456789 HTTP/1.1" 200 455 "-" "curl/7.26.0"
$magicString = "raspberrypiPhoneHome";
# modify as needed for your situation...
$accessLog = "/var/log/drjohns/access.log";
# pick up timestamp in access file
$piTime = `grep $magicString $accessLog|tail -1|cut -d\? -f2|cut -d' ' -f1`;
$curTime = time();
$date = `date`;
# your PID file is somewhere else. It tells us when Apache was started.
# you could comment out these next lines just to get started with the program
$PID = "/var/run/";
($atime,$mtime,$ctime) = (stat($PID))[8,9,10];
$diff = $curTime - $piTime;
print "magicString, accessLog, piTime, curTime, diff: $magicString, $accessLog, $piTime, $curTime, $diff\n" if $DEBUG;
print "accessLog stat. atime, mtime, ctime: $atime,$mtime,$ctime\n" if $DEBUG;
if ($curTime - $ctime < $maxDiff) {
  print "Apache hasn't been running long enough yet to look for something in the log file. Maybe next time\n";
$goodFile = "/tmp/piGood";
$errorFile = "/tmp/piError";
# Think of it as state machine. There are just a few states and a few transitions to consider
if (-e $goodFile) {
  print "state: good\n" if $DEBUG;
  if ($diff < $maxDiff) {
    print "Remain in good state\n" if $DEBUG;
  } else {
# transition to error state
    print "Transition from good to error state at $date, diff is $diff\n";
    sendMail("Good","Error","Last call was $diff seconds ago");
# set state to Error
    system("rm $goodFile; touch $errorFile");
} elsif (-e $errorFile) {
  print "state: error\n" if $DEBUG;
  if ($diff > $maxDiff) {
    print "Remain in error state\n" if $DEBUG;
  } else {
# transition to good state
    print "Transition from error to good state at $date, diff is $diff\n";
    sendMail("Error","Good","Service restored. Last call was $diff seconds ago");
# set state to Good
    system("rm $errorFile; touch $goodFile");
} else {
  print "no state\n" if $DEBUG;
  if ($diff < $maxDiff) {
    system("touch $goodFile");
    sendMail("no state","Good","NA") if $DEBUG;
    print "Transition from no state to Good at $date\n";
# don't send alert
  } else {
    print "Remain in no state\n" if $DEBUG;
sub sendMail {
($oldState,$state,$additional) = @_;
print "oldState,state,additional: $oldState,$state,$additional\n" if $DEBUG;
$subject = "$state : $monitorName";
open(MAILX,"|mailx -r \"$mailsender\" -s \"$subject\" $recipient") || die "Cannot run mailx $mailsender $subject!!\n";
print MAILX qq(
$monitorName is now in state: $state
Time: $date
Former state was $oldState
Additional info: $additional
- sent from pialert program
sub usage {
  print "usage: $0 -m <maxDiff (seconds)> [-d (debug)]\n";

This is called from my server’s crontab. I set it like this:

 Call monitor that sends an alert if my Raspberry Pi fails to phone home - DrJ 2/13
0,5,10,15,20,25,30,35,40,45,50,55 * * * * /home/drj/ -m 300 >> /tmp/pialert.log

My /tmp/pialert.log file looks like this so far:

Transition from no state to Good at Wed Feb  6 12:10:02 EST 2013
Apache hasn't been running long enough yet to look for something in the log file. Maybe next time
Apache hasn't been running long enough yet to look for something in the log file. Maybe next time
Transition from good to error state at Fri Feb  8 10:55:01 EST 2013, diff is 420
Transition from error to good state at Fri Feb  8 11:05:02 EST 2013, diff is 1

The last two lines result from a test I ran – i commented out the crontab entry on my Pi to be absolutely sure it was working.

The error message I got in my email looked like this:

Subject: Error : Raspberry Pi phone home
Raspberry Pi phone home is now in state: Error 
Time: Fri Feb  8 10:55:01 EST 2013
Former state was Good
Additional info: Last call was 420 seconds ago
- sent from pialert program

Why not use Nagios?
Some will realize that I replicated functions that are provided in Nagios, why not just hang my stuff off that well-established monitoring software? I considered it, but I wanted to stay light. I think my approach, while more demanding of me as a programmer, keeps my server unburdened by running yet another piece of software that has to be understood, debugged, maintained and patched. If you already have it, fine, by all means use it for the alerting part. I’m sure it gives you more options. For an approach to installing nagios that makes it somewhat manageable see the references.

A few words about sending mail
I send mail directly from my cloud server, I have no idea what others do. With Amazon, my elastic IP was initially included in blacklists (RBLs), etc, so I really couldn’t send mail without it being rejected. they have procedures you can follow to remove your IP from those lists, and it really worked. Crucially, it allowed me to send as a TXT message. Just another reason why you can’t really beat Amazon hosting (there was no charge for this feature).

And sending TXT messages
I think most wireless providers have an email gateway that allows you to send a TXT message (SMS) to one of their users via email (SMTP) if you know their cell number. For instance with Verizon the formula is




We have assembled a working power/Internet service monitor as a DIY project for a Raspberry Pi. If you want to use your Pi for a lot of other things I suggest to leave this one for your power monitor and buy another – they’re cheap (and fun)!

I will now know whenever I lose power – could be any minute now thanks to Nemo – and when it is restored, even if I am not home (thanks to my SmartPhone). See in my case my ISP, CenturyLink, is pretty good and rarely drops my service. JCP&L, not so much.

Admittedly, most people, unlike me, do not have their own cloud-hosted server, but maybe it’s time to get one?

Open Monitoring Distribution (OMD) makes installing and configuring nagios a lot easier, or so I am told. It is described here.
I’ve gotten my mileage out of the monitor perl script in this post: I’ve recently re-used it with modifications for a similar situation except that the script is being called by HP SiteScope, and, again, a Raspberry Pi is phoning home. Described here.

Apache Linux Network Technologies Perl Raspberry Pi

Getting started on my Raspberry Pi

The Raspberry Pi computer is an awesome idea. Its performance is surprisingly good as well, as I will show below. Available packages? Not so impressive. I share some old X-windows tricks which will allow you to bring up the GUI without ever using the HDMI port.

The details
My Methodology
I was too lazy to set up an HDMI console plus keyboard and mouse. I’m more a server guy anyways so I’m more interested in what I can accomplish from a command prompt. And this also makes getting started that much easier. I had burned the Raspbian Wheezy image to a super-fast SD card (more on that below) the day that my Pi came in the mail. I attached power and ethernet, booted it up, guessed the IP it acquired by running some PINGs, did an ssh using the pi/raspberry user and Bingo! I was in. It couldn’t be easier. How I tested GUI applications without a console is explained further down below.

First Impressions
It feels fast.

Not much seems to be there by default – no apache, not many X utilities. There is a lame X browser called x-www-browser. I thought this is Debian, right? So we can just start downloading Debian packages, like Firefox. Wrong! It doesn’t work that way. There’s no Firefox, Safari, Chrome or Opera! It does come pre-loaded with curl, however, ha, ha.

No, the Raspbian FAQ explains why this is. It’s rather complicated. I guess the compiler works though I haven’t tested it yet. So I suppose you could compile packages from their source code.

The x-terminal-emulator is pretty decent, however.

If it comes with a web server, I didn’t notice. So I quickly checked for the availability of apache. It’s available. Then installed it:

> sudo apt-get install apache2

That worked out well. It installed it and the packages it depended on and even launched it, and it all felt fairly peppy. See the suggested fix further down if this gives you errors. The default HTML DOCROOT is /var/www. I accessed it locally:

> curl localhost

And a welcome message displayed. A good start.

Where’s the rest of my 16 GB SD card gone to?

Original disk layout:

pi@raspberrypi:~$ df -k
Filesystem     1K-blocks    Used Available Use% Mounted on
rootfs           1804128 1492908    219572  88% /
/dev/root        1804128 1492908    219572  88% /
devtmpfs          224436       0    224436   0% /dev
tmpfs              44900     204     44696   1% /run
tmpfs               5120       0      5120   0% /run/lock
tmpfs              89780       0     89780   0% /run/shm
/dev/mmcblk0p1     57288   16872     40416  30% /boot

Layout after raspi-config:

pi@raspberrypi:~$ df -k
Filesystem     1K-blocks    Used Available Use% Mounted on
rootfs          15251960 1494852  12982544  11% /
/dev/root       15251960 1494852  12982544  11% /
devtmpfs          224436       0    224436   0% /dev
tmpfs              44900     196     44704   1% /run
tmpfs               5120       0      5120   0% /run/lock
tmpfs              89780       0     89780   0% /run/shm
/dev/mmcblk0p1     57288   16872     40416  30% /boot

Whew! That was easy. All 16 GB accounted for and actively used.

Was it worth it to buy that UHS SD card?
I didn’t want a sluggish server, so I paid a couple bucks more and bought a 16 GB SD UHS (ultra high speed) card for my “disk,” not knowing whether or not the Pi had the muscle to put it to work.

A quick aside about SD cards
I did a quickie self-education on this topic. Most SD cards are rated by class, so a class 4 SD card can do 4 MB/sec I/O, and a class 10 card can do at least 10 MB/sec. Faster still are the UHS SD cards. My Sandisk, which only cost about $19, is rated for 45 MB/sec I/O. A great write-up on this topic specifically for Raspberry Pi is: Raspberry Pi SD Card Speed Test – Raspberry Pi benchmark (higher numbers are better)
1333 file creation/destruction operations per second – Raspberry Pi with UHS SD card
6666 file creation/destruction operations per second – EBS volume on small image running CentOS in Amazon cloud
26000 file creation/destruction operations per second – high-end HP server (G7 DL380) running SLES 11

I think I provided the source for this simple Perl program I wrote, It creates a file, writes a random number into it, then deletes it – that all counts as one operation. Here it is:

# DrJ, 1/2000
# Test disk I/O
$DIR = $ARGV[0];
$t0 = time();
while(1) {
  $ran = rand();
  open(FILE,"&gt;$ran") || die "Cannot open file $ran in directory $DIR!!\n";
  print FILE $ran;
  if ($cnt % 20000 == 0) {
    $rate = $cnt / (time() - $t0) ;
    print "File creation/desctruction rate: $rate\n";

DrJ 2017 Note: The notes below are historical and does not seem to work at all for the Raspberry Pi 3 loaded with NOOBS. In NOOBS you select your OS to install. You can’t ssh to it. I know. I just tried! Even after you install Raspbian Wheezy, you still can’t access it via ssh until you enable the ssh daemon with raspi-condfig.

How to get the GUI working without a console
I have this feeling that many people trying out the Pi won’t have the faintest idea how X windows works, unlike us Unix old-timers. It’s fun to put 20-year-old lessons to work on something new. Like I said I’m lazy and didn’t feel the need to set up an actual console to the thing. I used some old X features to allow me to launch specific X-windows applications that are pre-loaded on the device, and display them on my PC. How?

On a Windows PC you install Cygwin. Then launch the XWin Server. You ssh to your pi. How do you know its IP the first time? Guess! It picks it up via DHCP, so start PINGing around the range where your other devices are numbered. My PC is, my pi was Maybe you have a bunch of devices responding to PING and are unsure which is which? Your MAC table is your friend. Here’s mine:

C:\Documents and Settings&gt;arp -a
Interface: --- 0x2
  Internet Address      Physical Address      Type           00-14-f6-e0-c0-4c     dynamic          b8-27-eb-dd-21-02     dynamic          00-90-a9-bb-3d-76     dynamic

arp displays the MAC table with the IP-to-physical (MAC) address correspondence. So most Pi’s will have a MAC address whose beginning is similar to b8-27-eb. A quick aside. Does the MAC address follow the board (SOC) or the SD Card? The board – I tested this with a friend’s SD Card.

You login with the pi/raspberry.

Then set your DISPLAY environment variable:

> export DISPLAY=

Most of your X applications begin with the letter “x,” so enter

> x<tab><tab>

to see a display of available programs like this:

xapian-config        xdg-screensaver      xkbevd               xpdf.real            xxd
xarchiver            xdg-settings         xkbprint             xprop                xz
xargs                xdpyinfo             xkbvleds             x-session-manager    xzcat
xauth                xdriinfo             xkbwatch             xsubpp               xzcmp
xdg-desktop-icon     xev                  xkill                xtables-multi        xzdiff
xdg-desktop-menu     xfd                  xlsatoms             x-terminal-emulator  xzegrep
xdg-email            xfontsel             xlsclients           xvinfo               xzfgrep
xdg-icon-resource    xinit                xlsfonts             x-window-manager     xzgrep
xdg-mime             xkbbell              xmessage             xwininfo             xzless
xdg-open             xkbcomp              xpdf                 x-www-browser        xzmore

Actually I don’t know how many of these are X. But at least a few are.

Start an xterm in Cygwin. In the xterm window, give permission to the Pi to use it as its Xserver:

> xhost +

Now in the Pi shell (ha, ha), type:

> x-terminal-emulator

and you should see the colorful terminal emulator on your PC in a few seconds. this is a true GUI application. You similarly launch the x-www-browser. Don’t forget to background your X-windows in the Pi shell:

> bg

so you can use the one window to launch multiple X windows.

Another example the book Programming the Raspberry Pi has is the Python interactive development environment. I reasoned from the screen shots that idles3 would also be an X application – hey, they don’t have to start with the letter x – and indeed it is!

Want the whole ball of wax, a complete console? I just figured this one out by taking an educated guess:

> x-session-manager

and you will see the complete GUI on your PC! Cool, huh?

Want to get rid of the last thing you backgrounded, like, say, that x-session-mnager which has taken over your PC?! Type

> fg

and it will be killed.

How to get the GUI working without a console, Method 2
The above steps look a little daunting? Even I don’t want to install cygwin on my new PC. There is an alternative which can suffice for light usage.

On the Pi install a vnc server:

$ sudo apt-get install tightvncserver

Launch it:

$ vncserver

The first time only it will ask you to set up a password. Might as well make it raspberry like everything else we do on the Pi.

Then install a VNC client on your PC (Or Macbook). I use RealVNC.

Launch your VNC client and connect to your Pi’s IP address (which you need to know) + the display number, like this:

For a Pi at IP in which the vncserver started display 1. Normally it will be display 1, but I guess it might be display 0.

Don’t launch vncserver more than once! You don’t want a bunch of those running and dragging on performance.

Anyways, that’s it! You should see the Pi’s GUI on your PC, but it might seem a wee bit small.

Setting a static IP
If you’re going to use the Pi more as a server like I am, I think it’s a good idea to give it a static IP. What I did is to edit /etc/network/interfaces. Mine now looks like this:

Nagios can be installed! That's pretty cool - it's a sophisticated network monitoring utility.

Get a decent browser
The web browsers that come with the Pi are horrible. Midori? Seriously? I found you can get Firefox, but the downside is that it’s sloooww. But at least it works. The secret is that it’s not called Firefox. Instead:

$ sudo apt-get install iceweasel

Yes, it’s iceweasel, not Firefox, in Debian Linux. Go figure.

My cool transparent case
I recommend to get a case. I got the one with the best reviews. It’s kind of expensive, about $20, but worth it. It’s practically a work-of-art. Clear, the PC board fits snugly. I put it in my pocket and showed it around to my friends, feeling it was well protected, and yet also a sight to behold the first time. I even has a thoughtful light guide so the LEDs look beautiful as their light follows the rectangular opening to open air. I never had this much fun in show-and-tell! I just pulled the Pi wrapped in its case from my shirt pocket and amazed those around me. So go ahead and splurge. Anyways some of the cheaper cases look just that. Here is what I bought:

Helping a friend out with his Pi
So I dutifully take my friend’s Pi home and offer to install a web server. What did I do wrong? Well, duh, I could have just taken his SD Card home and plugged it into my Pi case! That concept takes some getting used to! We all have the same hardware. Our SD cards – our disk – are what make one Pi different from another.

So I followed my own blog post to recall some things. This Pi also had a MAC address beginning with the same six characters.

The apache2 installation did not work out, however. What to do? Well, I eventually read the darn output from running it. It suggests to try this:

> sudo apt-get update

So I ran that, figuring it could do no harm. Then I re-ran

> sudo apt-get install apache2

and this time the install actually worked!

Reading a flash drive
I was curious to see if you could stick a flash drive in the thing and just read it. I didn’t think so since I thought it would be formatted for NTFS. But if you have the GUI running and bring up a file manager, I’ll be darned if it doesn’t just work. I noticed the drive is mounted as /media/Cruzer (my flash drive has the brand name Cruzer).

If you don’t launch the file manager, I think you can still work with it as follows:

$ sudo mkdir /media/Cruzer; sudo mount /dev/sda1 /media/Cruzer

Then when you’re all done and before you remove it:

$ sudo umount /media/Cruzer

So that’s pretty cool. You can create tar archives on the flash drive, plug it into someone else’s Pi and untar it, etc, just like on Windows.

Raspberry Pi is respectable as a computer. It will be a lot of fun to explore for the hobbyist.


Raspberry Pi SD Card Speed Test – Raspberry Pi – a great discussion of the various speeds of Micro SD cards and how to measure yours
Go here for my next project – using your Raspberry Pi to monitor your home’s power or Internet connection.
Interested in networking? A lot of useful tips can be found in this posting describing how to turn your Pi into a router. distributes realVNC viewers for various platforms.
How about a Raspberry Pi-driven digital photo frame? I describe an approach in this article.
Brief Nagios for Raspberry Pi writeup.

JavaScript Linux Perl

A simple Perl script to build JavaScript folder objects

Part 2
This is the 2nd part in a two-part blog where I present a simple example of a JavaScript folder browser. In Part 1 I provided all the JavaScript required. By itself it may have seemed an academic exercise, but once you appreciate that it isn’t hard to write a program which creates the JavaScript objects from your server’s directory structure, well, now you have something that’s pretty powerful and useful.

The details
I considered writing this in Python, which seems to be a more current language, but old habits die hard as they say. I just know Perl too well to suffer the pain of learning all those neat tricks all over again in another language. Maybe someday I’ll re-write it in Python.
Notice the recursion through the directories? I first used that 17 years ago! Why throw out good code?

Here is the code, which I named

# DrJ - 7/2012
# scan picture-containing directories using recursion and build javascript objects from them
use Getopt::Std;
$homedir = $opt_d;
$jsfile = $opt_j;
usage() if ! $opt_d || ! $opt_j;
$DEBUG = 0;
print "Homedir: $homedir, jsfile: $jsfile\n";
open(JS,">$jsfile") || die "Cannot open JavaScript file: $jsfile!!\n";
$date = `date +%D`;
($homedirnoslash) = $homedir =~ /^\/(.+)/; # assumes leading "/"
# print opening of function
print JS qq#function init() {
// Generated data from - DrJ $date
folder['browse'] = {path:'',depth:0,kids:['$homedirnoslash']};
# get things going with our recursive function
# closing statement
print JS qq(}\n);  # close of init JavaScript function
sub traverse {
my ($dir,$depth) = @_;
my @kids = ();
print "Traverse. dir: $dir\n" if $DEBUG;
opendir(DIR, $dir) || die "Cannot open dir $dir!!\n";
foreach (readdir(DIR)) {
  next if $_ eq '.' || $_ eq '..';
  print "Traverse. file: $_\n" if $DEBUG;
  $path = "$dir/$_";
  if (-d $path) {         # a directory
# we want only the last part of the path
    (my $lastpath) = $path =~ /([^\/]+)$/;
    traverse($path,$depth + 1); # recurse!
  } elsif ($_=~/$filespec/) {        #
} # end loop over files in this directory
# write out the JS objects
print JS qq(folder["$dir"] = {path:"$dir",depth:$depth,kids:[);
my $i = 0;
# kids are in jumbled order.  Do regular sort on them.
foreach (sort @kids) {
  $comma = $i++ > 0 ? "," : "";
  print JS qq($comma"$_");
# end of object. close it out.
print JS qq(]};\n);
} # end sub traverse
sub usage {
  print "usage: $0 -d root_directory -j JavaScript_output_file\n";

It’s pretty self-explanatory. Call it like this example:

> ./ -d /homepic -j init.js

and it produces an init.js file filled with an init() function and all the necessary folder objects, assuming the top-level folder to browse is /homepic.

My init.js looks like this:

function init() {
// Generated data from - DrJ 07/27/12
folder['browse'] = {path:'',depth:0,kids:['homepic']};
folder["/homepic/pictures_chronological/2011_06"] = {path:"/homepic/pictures_chronological/2011_06",depth:2,kids:[]};
// lots more lines like this omitted
folder["/homepic"] = {path:"/homepic",depth:0,kids:["kodak_pictures","pictures_chronological"]};

And I tested it in browse13.html, which looks just like browse12.html, except I got rid of the init() function and added an include line at the top:

<script type="text/javascript" src="init.js"></script>

I am a little concerned about performance. This clearly isn’t designed to scale to tens of thousands of directories, but will it be sufficiently fast for my purposes? My init.js is 213 lines and about 25 KB in size. browse13.html which calls it loads fast and runs fast. So, yes, success!

Part 1, A Simple Javascript Folder Browser

We have created a fairly powerful and general-purpose folder browser out of fairly simple usage of JavaScript and Perl. It makes an ideal base upon which to build further.

Apache JavaScript Perl

A Simple Javascript Folder Browser

Part 1

I haven’t posted much lately. I’ve been tied up creating this folder browser using client-side JavaScript. I probably made every mistake in the book, but I worked through them all and the outcome is pretty cool, if I say so myself! It works in IE, FireFox and even Blackberry!

The details
I broke down the development of this browse app into 12 stages. Given time, I might show the progression of my thinking as each version becomes closer and closer to fulfilling all initial objectives. But who has time? I’ll show the source for browse3.html, warts and all, and then skip many iterations and jump to showing the final source, browse12.html.

It ain’t pretty. It isn’t even correct. But it “does stuff.” It assumes Apache web server is running and “borrows” the closed and open folder icons from apache’s /icons directory. In my case I have a top-level directory called /homepic with folders under that and sub-folders under those folders that I want the ability to browse and , ultimately, take some action such as displaying all the folder’s images in the image viewer I wrote earlier.

<!DOCTYPE html>
<script type="text/javascript">
// global object
var folder = new Object;
function displayDate()
function init() {
// big initialization - generated code from perl perusal of directories
// see
//  var folder = new Object;
// we need this empty assignment to extend object with subproperties later on
  folder['homepic'] = '/homepic';
  //folder['/homepic'].path = '/homepic';
  folder.homepic.state = 'closed';
  folder[0] = '/homepic/kodak_pictures';
  folder[1] = '/homepic/pictures_chronological';
  folder['/homepic/kodak_pictures'] = '/homepic/kodak_pictures';
  folder['/homepic/kodak_pictures'].state = 'closed';
  //folder['/homepic/kodak_pictures'].path = '/homepic/kodak_pictures';
  folder['/homepic/pictures_chronological'] = '/homepic/pictures_chronological';
  folder['/homepic/pictures_chronological'].state = 'closed';
  //folder['/homepic/pictures_chronological'].path = '/homepic/pictures_chronological';
  var child = 'homepic';
  var cstate = folder['homepic'].state;
  var cpath = folder[0];
function browse(f) {
document.getElementById("demo").innerHTML="folder: "+f+" ";
var icon;
var imgid;
var fname;
if (f == "browse") {
// see
// one-time initialization
  icon = document.createElement('IMG');
  icon.src = "/icons/folder.gif"; = "icon-/homepic";
  icon.onclick = Function('browse("/homepic")');
  var divfolder = document.createElement('DIV'); = "/homepic";
  var x = document.createTextNode('homepic');
  //document.getElementById("browse").innerHTML='<img id="homepic" onclick="browse(\'homepic\')" src="/icons/folder.gif">ho
} else {
  imgid = 'icon-' + f;
// change img to one of open folder
  document.getElementById(imgid).src = "/icons/";
  // nope? imgid.src  = "/icons/";
  for (i=0;i<3;i++) {
    icon = document.createElement('IMG');
    icon.src = "/icons/folder.gif";
    fname = folder[f].children[i];
    //fname = folder['homepic'].children[i]; = "icon-" + fname;
    icon.onclick = Function('browse('+fname+')');
    var divfolder = document.createElement('DIV'); = fname;
    var x = document.createTextNode(fname);
  } // end loop over children
// note variable # or arguments are being passed
function  openfolder()
var f = arguments[0];
var dir = "/icons/";
var fopen = "";
var fclosed = "folder.gif";
var folder = document.getElementById(f);
var ftype = folder.src;
// src includes http... Get rid of stuff in front
var patt = /.*(folder.+)/;
var ftypebare = ftype.replace(patt,"$1");
// for debugging
document.getElementById("demo").innerHTML="folder: "+f+" "+ftypebare;
if (ftypebare == fopen) {
// close folder and remove sub-folders
  folder.src = dir+fclosed;
} else {
// open up folder and reveal sub-folders
  folder.src = dir+fopen;
  for (var i = 0; i < arguments.length; i++) {
    var placeid = arguments[i];
    var srcid = '/' + placeid;
    document.getElementById(placeid).innerHTML='&nbsp;&nbsp;&nbsp;<img id="' + srcid + '" onclick="openfolder(\'pictures_ch
ronological\')" src="/icons/folder.gif"/> pictures_chronological<br>';
<h1>Folder Browser</h1>
<p id="demo">Debug Aid.</p>
<p id="browse"><a href="#" onclick='browse("browse")'>Folder Browser</a></p>
<img id="homepic" onclick="openfolder('homepic','homepic/pictures_chronological','homepic/canon_pictures')" src="/icons/fol
der.gif"/> homepic<br>
<div id="homepic/pictures_chronological"></div>
<div id="homepic/canon_pictures"></div>
<img id="cfolder2" onclick="openfolder(2)" src="/icons/folder.gif"/><br>
<img id="cfolder3" onclick="openfolder(3)" src="/icons/folder.gif"/><br>
<img id="cfolder4" onclick="openfolder(4)" src="/icons/folder.gif"/><br>

So you see in browse3 I’m wrestling with how to work with JavaScript Objects (which I didn’t really know existed at that time). I badly wanted to give an associative array properties, as in the initialization line

folder['/homepic/kodak_pictures'].state = 'closed';

but I couldn’t find any examples on the Internet. I eventually learned that wasn’t a correct assignment.

So one of my biggest and most worthwhile lessons was to gain a decent understanding of JavaScript objects, which hold multiple values, and object properties.

I tried to use Firebug for Firefox, with very limited success, but at least I could step through the Javascript code and see which branch in a conditional was being executed compared to what I thought should be executed, which tipped me off to one vexing problem concerning opening and closing folders multiple times. Also just looking up the error in Internet Explorer by double-=clicking the warning sign in the corner was tremendously helpful.

So…skipping for now versions 4 – 11, we arrive at browse12.html:


<!DOCTYPE html>
<script type="text/javascript">
// global object
var folder = new Object;
function displayDate()
function init() {
// big initialization - generated code from perl perusal of directories
// I think my big breakthrough was to learn about Javascript objects and their properties
// from the book Javascript The Definitive Guide, 5th edition by D.Flanagan
// Some additional inspiration came from
// folder is an associative array with properties path, state,depth and kids (which is itself an array)
// first entry is initial top-level to get things started
  folder['browse'] = {path:'',depth:0,kids:['homepic']};
// regular entries:
  folder['/homepic'] = {path:'/homepic',depth:1,kids:['kodak_pictures','pictures_chronological']};
// values for sub-folders
// /homepic/kodak_pictures
  folder['/homepic/kodak_pictures'] = {path:'/homepic/kodak_pictures',depth:2,kids:['2002_05','2002_06']};
// /homepic/pictures_chronological
  folder['/homepic/pictures_chronological'] = {path:'/homepic/pictures_chronological',depth:2,kids:['2011_11','2011_12']};
function browse(f) {
document.getElementById("demo").innerHTML="folder: "+f+" ";
var icon;
var imgid;
var fname;
var table;
if (f == "browse") {
// one-time initialization
imgid = 'icon-' + f;
if (!folder[f]) {
// folder not defined: must be a terminal folder. Do something here eventually
// but for now do nothing whatsoever
} else {
  if (folder[f].state === undefined || folder[f].state == 'closed') {
  // change img to one of open folder
    if (f == 'browse') {
    } else {
      document.getElementById(imgid).src = "/icons/";
    var kids = folder[f].kids;
    for(var i=0;  i < kids.length; i++) {
      table = document.createElement("table");
      table.border = 0;
      var row = document.createElement("tr");
      var td1 = document.createElement("td");
      var td2 = document.createElement("td");
      var td3 = document.createElement("td");
      icon = document.createElement("img");
      icon.src = "/icons/folder.gif";
      if (f == "browse") {
        fname = "/" + kids[i];
      } else {
        fname = f + "/" + kids[i];
      } = "icon-" + fname;
      if (folder[fname])
        folder[fname].state = 'closed';
      icon.onclick = Function('browse("'+fname+'")');
      td1.width = 27 + folder[folder].depth*27;
      td1.align = "right";
      var node = document.createTextNode(kids[i]);
      row.appendChild(td1); row.appendChild(td2); row.appendChild(td3);
      var divfolder = document.createElement("div"); = fname;
      folder[f].state = 'open';
    } // end loop over children
  } else {
  // set folder to closed state
  // this innerHTML nullification is kind of a kludge, but it works
    document.getElementById(imgid).src = "/icons/folder.gif";
    folder[f].state = 'closed';
  } // end conditional over folder state
} // end condition over whether folder is defined or not
} // end function browse
<h1>Folder Browser</h1>
<p id="demo">Debug Aid.</p>
<p id="browse"><a href="#" onclick='browse("browse")'>Folder Browser</a></p>

That’s it! Not bad, huh? I pan to generate the init() function periodically and automatically from a Perl script which peruses my directories.

I could have used Ajax and generated the subfolder information on the fly as it is needed – not that I know how, I just know enough to know it is possible and therefore I could do it – but I thought this method of pre-loading all the information might be a little more efficient. If this were a folder and file browser it would be different, but for now it is just a folder browser.

So the main revelation is that I had to set my associative array members to be objects during initialization, as in

folder['/homepic'] = {path:'/homepic',depth:1,kids:['kodak_pictures','pictures_chronological']};

and one of the object values is itself an anonymous array that holds the sub-folders.

Buying an actual book was probably a good move. I went with JavaScript, The Definitive Guide, 5th edition. Note that this is not the latest edition – the 6th – but this way I could buy the book used for a lot less and not get myself further confused by HTML5, which I am not ready to tackle and which many browsers do not yet fully support. The book is pretty heavy going and the discussion of DOM was particularly difficult and the examples too few and too removed from the real world. But the Core Javascript discussion made a lot of sense to me so was by itself worth the purchase price.

In my next post I’ve posted the Perl script which can generate the folder object initialization.

Part 2, A simple Perl script to build JavaScript folder objects

In this part one of a two-part post I’ve provided the JavaScript that implements a very compact folder browser. It has been tested on both IE and Firefox. The 2nd part of this series will provide the Perl Jvascript code generator for automation of the object creation.

Admin Internet Mail Linux Perl

The IT Detective Agency: last letter of attachment name is missing!

Today we bring you an IT whodunit thriller. A user using Lotus Notes informs his local IT that a process that emails SQL reports to him and a few others has suddenly stopped working correctly. The reports either contain an HTML attachment where the attachment type has been chopped to “ht” instead of “htm,” or an MHTML attachment type which has also been chopped, down to “mh” instead of “mht.” They get emailed from the reporting server to a sendmail mail relay. Now the convenient ability to double-click on the attachment and launch it stopped working as a result of these chopped filenames. What’s going on? Fix it!

Let’s Reproduce the Problem
Fortunately this one was easier than most to reproduce. But first a digression. Let’s have some fun and challenge ourselves with it before we deep dive. What do you think the culprit is? What’s your hypothesis? Drawing on my many years of experience running enterprise-class sendmail servers, and never before having seen this problem despite the hundreds of millions of delivered emails, my best instincts told me to look elsewhere.

The origin server, let’s call it aspen, sends few messages, so I had the luxury to turn on tracing on my sendmail server with a filter limiting the traffic to its IP:

$ tcpdump -i eth0 -s 1540 -w /tmp/aspen.cap host aspen

Using wireshark to analyze asp.cap and following the tcp stream I see this:

Content-Type: multipart/mixed;
This is a multipart message in MIME format
Content-Type: text/plain;
Content-Transfer-Encoding: 7bit
SQLplus automated report
Content-Type: application/octet-stream;
		 name="tower status_2012_06_04--09.25.00.htm"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
		 filename="tower status_2012_06_04--09.25.00.htm
<html><head></head><body><h1>Content goes here...</h1></body>

Result of trace of original email as received by sendmail

But the source as viewed from within Lotus Notes is:

Content-Type: multipart/mixed;
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
SQLplus automated report
Content-Type: application/octet-stream;
		 name="tower status_2012_06_04--09.25.00.htm"
Content-Disposition: attachment;
Content-Transfer-Encoding: base64

Same email after being trasferred to Lotus Notes

I was in shock.

I fully expected the message source to go through unaltered all the way into Lotus Notes, but it didn’t. The trace taken before sendmail’s actions was not an exact match to the source of the message I received. So either sendmail or Lotus Notes (or both) were altering the source in significant ways.

At the same time, we got a big clue as to what is behind the missing letter in the file extension. To highlight it, compare this line from the trace:

filename=”tower status_2012_06_04–09.25.00.htm

to that same line as it appears in the Lotus Notes source:

filename=”tower status_2012_06_04–

So there is no final close quote (“) in the filename attribute as it comes from the aspen server! That can’t be good.

But it used to work. What do we make of that fact??

I had to dig farther. I was suddenly reminded of the final episode of House where it is apparent that the solving the puzzle of symptoms is the highest aspiration for Doctor House. Maybe I am similarly motivated? Because I was definitely willing to throw the full weight of my resources behind this mystery. At least for the half-day I had to spare on this.

First step was to reproduce the problem myself. For sending an email you would normally use sendmail or mailx or such, but I didn’t trust any of those programs – afraid they would mess with my headers in secret, undocumented ways.

So I wrote my own mail sending program using Perl/Expect. Now I’m not advocating this as a best practice. It’s just that for me, given my skillset and perceived difficulty in finding a proper program to do what I wanted (which I’m sure is out there), this was the path of least resistance, the best and most efficient use of my time. You see, I already had the core of the program written for another purpose, so I knew it wouldn’t be too difficult to finish for this purpose. And I admit I’m not the best at Expect and I’m not the best at Perl. I just know enough to get things done and pretty quickly at that.

OK. Enough apologies. Here’s that code:

# - 6/2012
# Send mail by explicit use of the protocol
$DEBUG = 1;
use Expect;
use Getopt::Std;
$recip = $opt_r;
$sender = $opt_s;
$hostname = $ENV{HOSTNAME};
print "hostname,mailhost,sender,recip: $hostname,$opt_m,$sender,$recip\n" if $DEBUG;
$telnet = "telnet";
@hosts = ($opt_m);
$logf = "/var/tmp/smtpresults.log";
$timeout = 15;
$data = qq(Subject: test of strange MIME error
X-myHeader: my-value
From: $sender
To: $recip
Subject: SQLplus Report - tower status
Date: Mon, 4 Jun 2012 9:25:10 --0400
Importance: Normal
X-Mailer: ATL CSmtp Class
X-MSMail-Priority: Normal
X-Priority: 3 (Normal)
MIME-Version: 1.0
Content-Type: multipart/mixed;
This is a multipart message in MIME format
Content-Type: text/plain;
Content-Transfer-Encoding: 7bit
SQLplus automated report
Content-Type: application/octet-stream;
        name="tower status_2012_06_04--09.25.00.htm"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
        filename="tower status_2012_06_04--09.25.00.htm
<html><head></head><body><h1>Content goes here...</h1></body>
sub myInit {
# This structure is ugly (p.148 in the book) but it's clear how to fill it
@steps = (
        { Expect => "220 ",
          Command => "helo $hostname"},
# Envelope sender
        { Expect => "250 ",
          Command => "mail from: $sender"},
# Envelope recipient
        { Expect => "250 ",
          Command => "rcpt to: $recip"},
# data command
        { Expect => "250 ",
          Command => "data"},
# start mail message
        { Expect => "354 Enter ",
          Command => $data},
# end session nicely
        { Expect => "250 Message accepted ",
          Command => "quit"},
}       # end sub myInit
# Main program
open(LOGF,">$logf") || die "Cannot open log file!!\n";
foreach $host (@hosts) {
# create an Expect object by spawning another process
sub login {
($host) = @_;
#@params = ($host," 25");
$init_command = "$telnet $host 25";
#$Expect::Debug = 3;
my $exp = Expect->spawn("$init_command")
         or die "Cannot spawn $command: $!\n";
# Now run all the other commands
foreach $step (@steps) {
  $expstr = %{$step}->{Expect};
  $cmd = %{$step}->{Command};
#  print "expstr,cmd: $expstr, $cmd\n";
# Logging
  $exp->log_stdout(0);  # disable stdout for each command
  @match_patterns = ($expstr);
  ($matched_pattern_position, $error, $successfully_matching_string, $before_match, $after_match) = $exp->expect($timeout,
  unless ($matched_pattern_position == 1) {
    $err = 1;
  #die "No match: error was: $error\n" unless $matched_pattern_position == 1;
  # We got our match. Proceed.
}       # end loop over all the steps
# hard close
}       # end sub login

Code for

Invoke it:

$ ./ -m sendmail_host -s [email protected] -r [email protected]

The nice thing with this program is that I can inject a message into sendmail, but also I can inject it directly into the Lotus Notes smtp gateway, bypassing sendmail, and thereby triangulate the problem. The sendmail and Lotus Notes servers have slightly different responses to the various protocol stages, hence I clipped the Expect strings down to the minimal common set of characters after some experimentation.

This program makes it easy to test several scenarios of interest. Leave the final quote and inject into either sendmail or Lotus Notes (LN). Tack on the final quote to see if that really fixes things. The results?

Missing final quote

with final quote added

inject to sendmail

ht” in final email to LN; extension chopped

htm” and all is good

inject to LN

htm in final email; but extension not chopped

htm” and all is good

I now had incontrovertible proof that sendmail, my sendmail was altering the original message. It is looking at the unbalanced quote mark situation and recovering as best as possible by replacing the terminating character “m” with the missing double quote “. I was beginning to suspect it. After that shock drained away, I tried to check the RFCs. I figured it must be some well-meaning attempt on its part to make things right. Well, the RFCs, 822 and 1806 are a little hard to read and apply to this situation.

Let’s be clear. There’s no question that the sender is wrong and ought to be closing out that quote. But I don’t think there’s some single, unambiguous statement from the RFCs that make that abundantly apparent. Nevertheless, of course that’s what I told them to do.

The other thing from reading the RFC is that the whole filename attribute looks optional. To satisfy my curiosity – and possibly provide more options for remediation to aspen – I sent a test where I entirely left out the offending filename=”tower… line. In that case the line above it should have its terminating semicolon shorn:

Content-Disposition: attachment

After all, there already is a name=”tower…” as a Content-type parameter, and the string following that was never in question: it has its terminating semicolon.

Yup, that worked just great too!

Then I thought of another approach. Shouldn’t the overriding definition of the what the filetype is be contained in the Content-type header? What if it were more correctly defined as

Content-type: text/html


Content-type appears in two places in this email. I changed them both for good measure, but left the unbalanced quotations problem. Nope. Lotus Notes did not know what to with the attachment it displays as tower status_2012_06_04– So we can’t recommend that course of action.

What Sendmail’s Point-of-View might be
Looking at the book, I see sendmail does care about MIME headers, in particular it cares about the Content-Disposition header. It feels that it is unreliable and hence merely advisory in nature. Also, some years ago there was a sendmail vulnerability wherein malformed multipart MIME messages could cause sendmail to crash (see So maybe sendmail is just a little sensitive to this situation and feels perfectly comfortable and justified in right-forming a malformed header. Just a guess on my part.

Case closed.

We battled a strange email attachment naming error which seemed to be an RFC violation of the MIME protocols. By carefully constructing a testing program we were easily able to reproduce the problem and isolate the fault and recommend corrective actions in the sending program. Now we have a convenient way to inject SMTP email whenever and wherever we want. We feel sendmail’s reputation remains unscathed, though its corrective actions could be characterized as overly solicitous.

Perl Python

Help with the NPR Weekend Puzzle – and Learning Python

As I mentioned in my review of Amazon’s Web Services Summit, Python seems to be the vogue scripting language these days. I decided I had better dust off the brain cells and try it out. I am an old Perl stalwart, but one senses that that language has sort of hit a wall after enthusiasm from 10 years ago began to wane. One of my example Perl scripts is provided in my post about turning HP SiteScope into SiteScope Classic. After deciding I needed a Python project only a few days passed before I came across what I thought would be a worthy challenge – simple yet non-trivial. That is the weekend puzzle as I understand it on NPR.

The Details
Start with a one-syllable, four-letter common boy’s name. Adjust all the letters with the ROT-13 cipher, and arrive at a common two-syllable girl’s name? What are the names? I’m pretty sure I could have figured out how to do this in Perl. Python? If it lived up to its hype then it should also be up to the task IMHO.

About the Weekend Puzzle
I listen to it most weekends. I often end up listening to it twice! I always think of whether it is suitable to be programmed or not. Most often I find it is not. I mean not suitable for the simple scripts and such that I write. I’m not talking about IBM’s Jeopardy-playing Watson! But this weekend I feel that the ROT-13 part of the challenge can definitely be aided by programming. Is that cheating? If I “give away” my solution as I am then I remove my unfair advantage in knowing a thing or two about programming!

The program –

# drJ test script - 4/2012
# to get input agruments...
import sys
#inputName = raw_input("Enter name to be translated: ");
#print "Received input is : ", inputName
# and see
from string import maketrans
intab = "abcdefghijklmnopqrstuvwxyz"
outtab = "nopqrstuvwxyzabcdefghijklm"
trantab = maketrans(intab, outtab)
inputName = sys.argv[1]
print inputName,inputName.translate(trantab);

So you see Python has this great maketrans built-in function that we’re able to use to implement the ROT-13 cipher. Of course veterans will probably know an even simpler way to accomplish this, perhaps with the pack/unpack functions which I also considered using.

You call the script like this:

$ john

john wbua

I compiled a list of common four-letter names which I won’t fully divulge. They are in a file called names, one name per line. But how to quickly put it though this program? My old, bad lazy Unix habit was to do this:

$ cat names|while read line; do $line >> /tmp/results

I’ve got it memorized so I lose no time except typing the characters. But I also know the modern way is xargs.

xargs is the really hard part
I keep thinking that xargs is a good habit and one I should get into. But it’s not so easy. It took me awhile to find the appropriate example. And then you run across the debate that holds that Gnu parallel is still the better tool. Anyhow, here’s the xargs way…

$ cat names|xargs -I {} {}|more

amit nzvg
amos nzbf
arno neab
axel nkry

This little python program speaks volumes about the versatility of this language. It does have some really interesting properties and at first blush is worth getting to know better. No wonder others have embraced it. It also has helped us solve the weekend puzzle!

The stated answer? Glen and Tyra. You’ll see you can feed either one of these names into the program and come out with the other. I found it amusing that Will Shortz described the puzzle as “hard.” I didn’t think so – not with this program – but I was not the randomly selected winner, either, so I didn’t get a chance to explain how I did it.

The guy who did win explained that he simply wrote the ROT-13 version of the alphabet below the alphabet so he had a convenient look-up table. Clever.

Linux Perl Web Site Technologies

For Experimentalists: How to Test if your Web Server has a long timeout

I use the old Sun Java System Web Server, now known as the Oracle Web Server, formerly Sun ONE web server and before that iPlanet Web Server and before that Netscape Enterprise Server. The question came up the other day if the web server times out web pages. I never fully trust the documentation. I developed a simple method to experiment and find the answer for myself.

The Method
Sometimes you test what’s easiest, not what you should. In this case, an easy test is to write a long-running CGI program. This program,, is embarrassingly old, but anyhow…

# DrJ, 3/1999
# The new, PERL5 way:
use CGI;
$query = new CGI;
$| = 1;
print "Content-type: text/html\n\n";
print "<h2>Environment Variables</h2>
<tr><th>Env Variable</th><th>Value</th></tr>\n";
foreach $key (sort(keys(%ENV))) {
  print "<tr><td>$key</td><td>$ENV{$key}</td></tr>\n";
print "</table>\n";
print "<hr>
<h2>Name/Value Pairs</h2>
foreach $key ($query->param) {
  print "<tr><td>$key</td><td>" . $query->param($key) . "</td></tr>\n";
print "</table>\n";
$host = `hostname`;
print "Hostname: $host<br>\n";
print "we have slept for $ENV{QUERY_STRING} seconds.\n";

So you see it prints out some stuff, sleeps for a specified time, then prints out a final line. You call it like curl your_sevrer/cgi-bin/, where 305 is the time in seconds to sleep. I suggest use of the curl browser so as not to be thrown off by browser complications which may have their own timeouts. curl is simplicity itself and won’t bias the answer. Use a larger number for longer times. That was easy, right? Does it work? No. Does it show what we _really_ wanted to show? Also no. In other words, a CGI program that runs for 610 seconds will be killed by the web server, but that’s really a function of some CGI timer. Five and ten minutes seem to be magic timeout values for some built-in timers, so it is good to test times slightly smaller/larger than those times. So how do we test a plain web page??? It turns out we can…

The Solution – using the Unix bag of tricks
I only have a couple of minutes here. Briefly:

> mknod tmp.htm p

> chown me tmp.htm

(from another window)
> curl my_server/tmp.htm

(back to first window)
> sleep 610; ls -l > tmp.htm

Then wait! mknod as used above is apparently the old, Solaris, syntax. The syntax could be somewhat different under Linux. The point is to create a named pipe. Think of a named pipe, like it sounds, like giving a name to the “|” character used so often in Unix command lines. So it needs a process to give it input and a process to read it, hence the two separate windows.

See if you get the directory listing in your curl window after about 10 minutes. With my Sun Java System Web Server I do, so now I know both curl and the web server support probably unlimited page-load times.

An Unexpected Finding
Another tip and unexpected lesson – don’t use one of your named pipes more than once. If you mess up, create a new one and work with that. What happens when I re-use one of my pipes is that curl is able to read the web page over and over, without a process sending input to the named pipe! That wasn’t supposed to happen. What does it all mean? It can only be – -and I’ve often suspected this – that my web server is caching the content. It’s not a particularly well-documented feature, either. I think most times I wish it’d rather not.

The Sun Java System Web Server times out CGI scripts, but not regular static web pages. We proved this in a few minutes by devising an unambiguous experiment. As an added bonus we also proved that the web server caches at least some pages. The careful observer is always open to learning more than what he or she started out intending to look for!

Admin Perl Web Site Technologies

Turning HP SiteScope into SiteScope Classic with Perl

HP siteScope is a terrific web application tool and not too expensive for those who have any kind of a budget. The built-in monitor types are a bit limited, but since it allows calls to user-provided scripts your imagination is the only real limitation. For those with too many responsibilities and too little time on their hands it is a real productivity enhancer.

I’ve been using the product for 12 years now – since it was Freshwater SiteScope. I still have misgivings about the interface change introduced some years ago when it was part of Mercury. It went from simple and reliable to Java, complicated and flaky. To this day I have to re-start a SiteScope screen in my browser on a daily basis as the browser cannot recover from a server restart or who knows what other failures.

So I longed for the days of SiteScope Classic. We kept it running for as long as possible, years in fact. But at some point there were no more releases created for the classic view. So I investigated the feasibility of creating my own conversion tool. And…partially succeeded. Succeeded to the point where I can pull up the web page on my Blackberry and get the statuses and history. Think you can do that with regular HP SiteScope? I can’t. Maybe there’s an upgrade for it, but still. It’s nice to have the classic interface when you want to pull up the statuses as quickly as possible, regardless of the Blackberry display issue.

Looking back at my code, I obviously decided to try my hand at OO (object oriented) programming in Perl, with mixed results. Perl’s OO syntax isn’t the best, which addles comprehension. Without further ado, let’s jump into it.

The Details
It relies on something I noticed, that this URL on your HP SiteScope server, http://localhost:8080/SiteScope/services/APIConfigurationImpl?method=getConfigurationSnapshot, contains a tree of relationships of all the monitors. Cool, right? But it’s not a tree like you or I would design. Between parent and child is an intermediate layer. I suppose you need that because a group can contain monitors (my only focus in this exercise), but it can also contain alerts and maybe some other properties as well. So I guess the intermediate layer gives them the flexibility to represent all that, though it certainly added to my complication in parsing it. That’s why you’ll see the concern over “grandkids.” I developed a recursive, web-enabled Perl program to parse through this xml. That gives me the tools to build the nice hierarchical groupings. But it does not give me the statuses.

For the status of each monitor I wrote a separate scraper script that simply reads the entire daily SiteScope log every minute! Crude, but it works. I use it for an installation with hundreds of monitors and a log file that grows to 9 MB by the end of the day so I know it scales to that size. Beyond that it’s untested.

In addition to giving only the relationships, the xml also changes with every invocation. It attaches ID numbers to the monitors which initially you think is a nice unique identifier, but they change from invocation to invocation! So an additional challenge was to match up the names of the monitors in the xml output to the names as recorded in the SiteScope log. Also a bit tricky, but in general doable.

So without further ado, here’s the source code for the xml parser and main program which gets called from the web:

# Copyright work under the Artistic License,
# build v.simple SiteScope web GUI appropriate for smartphones
# 7/2010
# Id is our package which defines th Id class
use Id;
use CGI::Pretty;
my $cgi=new CGI;
$DEBUG = 0;
# GIF location on SiteScope classic
$ssgifs = "/artwork/";
$health{good} = qq(<img src="${ssgifs}okay.gif">);
$health{error} = qq(<img src="${ssgifs}error.gif">);
$health{warning} = qq(<img src="${ssgifs}warning.gif">);
# report CGI
$rprt = "/SS/rprt";
# the frustrating thing is that this xml output changes almost every time you call it
$url = 'http://localhost:8080/SiteScope/services/APIConfigurationImpl?method=getConfigurationSnapshot';
# get current health of all monitors - which is scraped from the log every minute by a hilgarj cron job
$monitorstats = "/tmp/monitorstats.txt";
print "Content-type: text/plain\n\n" if $DEBUG;
open(MONITORSTATS,"$monitorstats") || die "Cannot open monitor stats file $monitorstats!!";
  ($monitor,$status,$value) = /([^\t]+)\t([^\t]+)\t([^\t]+)/;
  $monitors{"$monitor"} = $status;
  $monitorv{"$monitor"} = $value;
open(CURL,"curl $url 2>/dev/null|") || die "cannot open $url for reading!!\n";
my %myobjs = ();
# the xml is one long line!
@lines = <CURL>;
#print "xml line: $lines[0]\n" if $DEBUG;
@multiRefs = split "<multiRef",$lines[0];
#parse multiRefs
# create top-level object
my $id = Id->new (
      id => "id0");
# hash of this object with id as key
$myobjs{"id0"} = $id;
# first build our objects...
foreach $mref (@multiRefs) {
  next unless $mref =~ /\sid=/;
#  id="id0" ...
  ($parentid) =  $mref =~ /id=\"(id\d+)/;
  print "parentid: $parentid\n" if $DEBUG;
# watch out for <item><key xsi:type="soapenc:string">groupSnapshotChildren</key><value href="#id3 ...
# vs <item><key xsi:type="soapenc:string">Network</key><value href="#id40"/>
  print "mref: $mref\n" if $DEBUG;
  @ids = split /<item><key/, $mref;
# then loop over ids mentioned in this mref
  foreach $myid (@ids) {
    next unless $myid =~ /href="#(id\d+)/;
    next unless $myobjs{"$parentid"};
# types include group, monitor, alert
    ($typebyregex) = $myid =~ />snapshot_(\w+)SnapshotChildren</;
    $parenttype = $myobjs{"$parentid"}->type();
    $type = $typebyregex ? $typebyregex : $parenttype;
    print "type: $type\n" if $DEBUG;
# skip alert definitions
    next if $type eq "alert";
    print "myid: $myid\n" if $DEBUG;
    ($actualid) = $myid =~ /href="#(id\d+)/;
    print "actualid: $actualid\n" if $DEBUG;
# construct object
    my $id = Id->new (
      id => $actualid,
      type => $type,
      parentid => $parentid );
# build hash of these objects with actualid as key
    $myobjs{$actualid} = $id;
# addchild to parent. note that parent should already have been encountered
    if ($myid !~ /groupSnapshotChildren/) {
# interesting child - has name (every other generation has no name!)
      ($name) = $myid =~ /string\">(.+?)<\/key/;  # use non-greedy operator
      print "name: $name\n" if $DEBUG;
# some names are not of interest to us: alerts, which end in "error" or "good"
      if ($name !~ /(error|good)$/) {
# name may not be unique - get extended name which include all parents
        if (defined $myobjs{"$parentid"}->parentid()) {
          $gdparid = $myobjs{"$parentid"}->parentid();
          $gdparname = $myobjs{"$gdparid"}->extname();
# extname -> extended, or distinguished name.  Should be unique
          $extname = $gdparname. '/' . $name;
        } else {
# 1st generation
          print "1st generation\n" if $DEBUG;
          $extname = $name;
        print "extname: $extname\n" if $DEBUG;
        $myobjs{"$parentid"}->hasnamedkids(1); # want to mark its parent as "special"
# we also need our hash to reference objects by extended name since id changes with each extract and name
may not be unique
        $myobjs{"$extname"} = $id;
      } # end conditional over desirable name check
    } else {
# now it's all parsed and our objects are alive. Let's build a web site!
# build a cookie containing path
my $pi = $ENV{PATH_INFO};
$script = $ENV{SCRIPT_NAME};
# Blackberry browser test
$BB = $ua =~ /^BlackBerry/i ? 1 : 0;
$MSIE = $ua =~ /MSIE /;
# font-size depends on browser
$FS = "font-size: x-small;" if $MSIE;
$cookie = $cgi->cookie("pathinfo");
$uri = $script . $pi;
$cookie=$cgi->cookie(-name=>"pathinfo", -value=>"$uri");
print $cgi->header(-type=>"text/html",-cookie=>$cookie);
($url) = $pi =~ m#([^/]+)$#;
#  -title=>'SmartPhone View',
# this doesn't work, sigh...
#print $cgi->start_html(-head=>meta({-http_equiv=>'Refresh'}));
print qq( <HEAD>
<meta http-equiv="Expires" content="0">
<meta http-equiv="Pragma" content="no-cache">
<meta HTTP-EQUIV="Refresh" CONTENT="60; URL=$url">
<TITLE>SiteScope Classic $url Detail</TITLE>
<style type="text/css">
a.good {color: green; }
a.warning {color: green; }
a.error {color: red; }
td {font-family: Arial, Helvetica, sans-serif; $FS} {font-family: Arial, Helvetica, sans-serif;}
<link rel="shortcut icon" href="/favicon.ico" type="image/x-icon" />
<script type=text/javascript>
function changeme(elemid,longvalue)
function restoreme(elemid,truncvalue)
#print $cgi->h1("This is the heading");
# parse path
# top lvl name:2nd lvl name:3rd lvl name
$altpi = $cgi->path_info();
print $cgi->p("pi is $pi") if $DEBUG;
#print $cgi->p("altpi is $altpi");
# relative url
$rurl = $cgi->url(-relative=>1);
if ($pi eq "") {
# the top
# top id is id3
  print qq(<p class="ss">);
  $myid = "id3";
  foreach $kid ($myobjs{"$myid"}->get_children()) {
    my $kidname = $myobjs{"$kid"}->name();
# kids can be subgroups or standalone monitors
    my $health = recurse("/$kidname");
    print "$health{$health} <a href=\"$rurl/$kidname\">$kidname</a><br>\n";
    $prodtest = $kid if $kidname eq "Production";
  print "</p>\n";
} else {
  $extname = $pi;
  print "pi,name,extname,script: $pi,$name,$extname,$script\n" if $DEBUG;
# print where we are
  $uriname = $pi;
  $uriname =~ s#^/##;
  #print $cgi->p("name is $name");
  #print $cgi->p("uriname is $uriname");
  $uricompositepart = "/";
  @uriparts = split('/',$uriname);
  $lastpart = pop @uriparts;
  print qq(<p class="ss"><a href="$script"><b>Sitescope</b></a><br>);
  print qq(<b>Monitors in: );
  foreach $uripart (@uriparts) {
    my $healthp = recurse("$uricompositepart$uripart");
# build valid link
    ##$link = qq(<a class="good" href="$script$uricompositepart$uripart">$uripart</a>: );
    $link = qq(<a class="$healthp" href="$script$uricompositepart$uripart">$uripart</a>: );
    $uricompositepart .= "$uripart/";
    print $link;
  my $healthp = recurse("$uricompositepart$lastpart");
  $color = $healthp eq "error" ? "red" : "green";
  print qq(<font color="$color">$lastpart</font></b></p>\n);
  print qq(<table border="1" cellspacing="0">);
  #print qq(<table>);
  %hashtrs = ();
  foreach $kid ($myobjs{"$extname"}->get_children()) {
    print "kid id: " . $myobjs{"$kid"}->id() . "\n" if $DEBUG;
    next unless $myobjs{"$kid"}->hasnamedkids();
    foreach $gdkid ($myobjs{"$kid"}->get_children()) {
      print "gdkid id: " . $myobjs{"$gdkid"}->id() . "\n" if $DEBUG;
      $gdkidname = $myobjs{"$gdkid"}->name();
      $gdkidextname = $myobjs{"$gdkid"}->extname();
      my $health = recurse("$gdkidextname");
      my $type = $myobjs{"$gdkid"}->type();
# dig deeper to learn health of the grankid's grandkids
      $objct = $healthct{good} = $healthct{error} = $healthct{warning} = 0;
      foreach $ggkid ($myobjs{"$gdkidextname"}->get_children()) {
        print "ggkid id: " . $myobjs{"$ggkid"}->id() . "\n" if $DEBUG;
        next unless $myobjs{"$ggkid"}->hasnamedkids();
        foreach $gggdkid ($myobjs{"$ggkid"}->get_children()) {
          print "gggdkid id: " . $myobjs{"$gggdkid"}->id() . "\n" if $DEBUG;
          $gggdkidname = $myobjs{"$gggdkid"}->name();
          $gggdkidextname = $myobjs{"$gggdkid"}->extname();
          my $health = recurse("$gggdkidextname");
      $elemid = "elemid" . $elemct;
# groups should have distinctive cell background color to set them apart from monitors
      if ($type eq "group") {
        $bgcolor = "#F0F0F0";
        $celllink = "$lastpart/$gdkidname";
        $truncvalue = qq(<font color="red">$healthct{error}</font>/$objct);
        $tdval = $truncvalue;
      } else {
        $bgcolor = "#FFFFFF";
        $celllink = "$rprt?$gdkidname";
# truncate monitor value to save display space
        $longvalue = $monitorv{"$gdkidname"};
        (my $truncvalue) = $monitorv{"$gdkidname"} =~ /^(.{7,9})/;
        $truncvalue = $truncvalue? $truncvalue : "&nbsp;";
        $tdval = qq(<span id="$elemid" onmouseover="changeme('$elemid','$longvalue')" onmouseout="restorem
      $hashtrs{"$gdkidname"} = qq(<tr><td bgcolor="#000000">$health{$health} </td><td>$tdval</td><td bgcol
or="$bgcolor"><a href="$celllink">$gdkidname</a></td></tr>\n);
# for health we're going to have to recurse
# print out in alphabetical order
  foreach $key (sort(keys %hashtrs)) {
    print $hashtrs{"$key"};
  print "</table>";
print $cgi->end_html();
sub recurse {
# to get the union of health of all ancestors
my $moniext = shift;
my ($moni) = $moniext =~ m#/([^/]+)$#;
# don't bother recursing and all that unless we have to...
return $myobjs{"$moniext"}->health() if defined $myobjs{"$moniext"}->health();
print "moni,moniext: $moni, $moniext\n" if $DEBUG;
my ($kid,$gdkidextname,$health,$cumhealth);
$cumhealth = $health = $monitors{"$moni"} ? $monitors{"$moni"} : "good";
foreach $kid ($myobjs{"$moniext"}->get_children()) {
    if ($myobjs{"$kid"}->hasnamedkids()) {
      foreach $gdkid ($myobjs{"$kid"}->get_children()) {
        $gdkidextname = $myobjs{"$gdkid"}->extname();
# for health we're going to have to recurse
        $health = recurse("$gdkidextname");
        if ($health eq "error" || $cumhealth eq "error") {
          $cumhealth = "error";
        } elsif ($health eq "warning" || $cumhealth eq "warning") {
          $cumhealth = "warning";
    } else {
# this kid is end of line
      $health = $monitors{"$kid"} ? $monitors{"$kid"} : "good";
        if ($health eq "error" || $cumhealth eq "error") {
          $cumhealth = "error";
        } elsif ($health eq "warning" || $cumhealth eq "warning") {
          $cumhealth = "warning";
return $cumhealth;
} # end sub recurse

I call it simply “ss” to minimize the typing required. You see it uses a package called which I wrote to encapsulate the class and methods. Here is

package Id;
# Copyright work under the Artistic License,
# class for storing data about an id
# URL (not currently protected): http://localhost:8080/SiteScope/services/APIConfigurationImpl?method=getC
# class for storing data about a group
use warnings;
use strict;
use Carp;
#group methods
# constructor
# get_members
# get_name
# get_id
# addmember
# member methods
# constructor
# get_id
# get_name
# get_type
# get_gp
# set_gp
sub new {
  my $class = shift;
  my $self = {@_};
  bless($self, "Id");
  return $self;
# get-set methods, p. 355
sub parentid { $_[0]->{parentid}=$_[1] if defined $_[1]; $_[0]->{parentid} }
sub isanamedid { $_[0]->{isanamedid}=$_[1] if defined $_[1]; $_[0]->{isanamedid} }
sub id { $_[0]->{id}=$_[1] if defined $_[1]; $_[0]->{id} }
sub name { $_[0]->{name}=$_[1] if defined $_[1]; $_[0]->{name} }
sub extname { $_[0]->{extname}=$_[1] if defined $_[1]; $_[0]->{extname} }
sub type { $_[0]->{type}=$_[1] if defined $_[1]; $_[0]->{type} }
sub health { $_[0]->{health}=$_[1] if defined $_[1]; $_[0]->{health} }
sub hasnamedkids { $_[0]->{hasnamedkids}=$_[1] if defined $_[1]; $_[0]->{hasnamedkids} }
# get children - use anonymous array, book p. 221-222
sub get_children {
# return empty array if arrary hasn't been defined...
  defined @{$_[0]->{children}} ? @{$_[0]->{children}} : ();
# adding children
sub addchild {
  $_[0]->{children} = [] unless defined  $_[0]->{children};
  push @{$_[0]->{children}},$_[1];

ss also assumes the existence of just a few of the images from SiteScope classic – the green circle for good, red diamond for error and yellow warning, etc.. I borrowed them SiteScope classic.

Here is the code for the log scraper:

# analyze SiteScope log file
# Copyright work under the Artistic License,
# 8/2010
$DEBUG = 0;
$logdir = "/opt/SiteScope/logs";
$monitorstats = "/tmp/monitorstats.txt";
$monitorstatshis = "/tmp/monitorstats-his.txt";
$date = `date +%Y_%m_%d`;
$file = "$logdir/SiteScope$date.log";
open(LOG,"$file") || die "Cannot open SiteScope log file: $file!!\n";
# example lines:
# 16:51:07 08/02/2010     good    LDAPServers     LDAP SSL test : exit: 0, 0.502 sec    1:
3481  0       502
#16:51:22 08/02/2010     good    Network DNS: (AMEAST) ns2  0.033 sec   2:3459      200     33      ok
#16:51:49 08/02/2010     good    Proxy   proxy.pac script on iwww    0.055 sec   2:12467 200     55   ok
     4288    1280782309      0    0  55      0       0      200  0
#16:52:04 08/02/2010     good    Proxy   Disk Space: earth /logs   66% full, 13862MB free, 41921MB total
 3:3598      66      139862
#16:52:09 08/02/2010     good    DrjExtranet  URL:     0.364 sec    1:3604      200
364  ok 26125   1280782328     0    0   358     4       2       200  0
while(<LOG>) {
  ($time,$date,$status,$group,$monitor,$value) = /(\S+)\s(\S+)\t(\S+)\t(\S+)\t([^\t]+)\t([^\t]+)/;
  print '$time,$date,$status,$group,$monitor,$value' . "$time,$date,$status,$group,$monitor,$value\n" if $DEBUG;
  next if $group =~ /__health__/; # don't care about these lines
  $mons{"$monitor"} = 1;
  push @{$mont{"$monitor"}} , $time;
  push @{$mond{"$monitor"}} , $date;
  push @{$monh{"$monitor"}} , $status;
  push @{$monv{"$monitor"}} , $value;
# open output at last moment to minimize chances of reading while locked for writing
open(MONITORSTATS,">$monitorstats") || die "Cannot open monitor stats file $monitorstats!!\n";
open(MONITORSTATSHIS,">$monitorstatshis") || die "Cannot open monitor stats file $monitorstatshis!!\n";
# write it all out - will always print the latest values
foreach $monitor (keys %mons) {
# dereference our anonymous arrays
  @times = @{$mont{"$monitor"}};
  @dates = @{$mond{"$monitor"}};
  @status = @{$monh{"$monitor"}};
  @value = @{$monv{"$monitor"}};
# last element is the latest measured status and value
  print MONITORSTATS "$monitor\t$status[-1]\t$value[-1]\n";
  print MONITORSTATSHIS "$monitor\n";
  #for ($i=-11;$i<0;$i++) {
# put latest measure on top
  for ($i=-1;$i>-13;$i--) {
    $time = defined $times[$i] ? $times[$i] : "NA";
    $date = defined $dates[$i] ? $dates[$i] : "NA";
    $stat = defined $status[$i] ? $status[$i] : "NA";
    $val = defined $value[$i] ? $value[$i] : "NA";
    print MONITORSTATSHIS "\t$time\t$date\t$stat\t$val\n";

As I said it gets called every minute by cron.

That’s it! I enter the url to access the main program which gets executed because I made /SS a CGI-BIN directory.

This gives you a read-only, Java-free view into your SiteScope status and hierarchy which beckons back to the good old days of Freshwater SiteScope.

Know your limits
What it does not do, unfortunately, is allow you to run a monitor – that seems like the next most simple thing which I should have been able to do but couldn’t figure out – much less define new monitors (never going to happen) or alerts.

I use this successfully against my HP SiteScope instance of roughly 400 monitors which itself is on a VM and there is no apparent strain. At some point this simple-minded script would no longer scale to suit the task at hand, but it might be good for up to a few thousand monitors.

And now a word about open source alternatives
Since I was so enamored with SiteScope Classic there seemed to be no compelling reason to shell out the dough for HP SiteScope with its unwanted interface, so I briefly looked around at free alternatives. Free sounds good, right? Not so much in practice. Out there in Cyberspace there is an enthusiast for a product called Zabbix. I just want to go on the record that Zabbix is the most confused piece of junk I have run across. You are getting less than what you paid for ($0) because you will be wasting a lot of time with it, and in the end it isn’t all that capable. Nagios also had its limits – I can’t remember the exact reason I didn’t go down that route, but there were definite reasons.

HP SiteScope is no panacea. “HP” and “stifling bureaucracy” need to be mentioned in the same sentence. Every time we renew support it is the most confusing mess of line items. Every time there’s a new cast of characters over at HP who nothing about the account’s history. You practically have to beg them to accept your money for a low-budget item like SiteScope because they really don’t pursue it in any way. Then their SAID and contract numbers stuff is confusing if you only see it once every few years.

A conversion program does exist for turning the finicky HP SiteScope Java-encumbered view into pure SiteScope Classic because I wrote it! But it’s a limited read-only view. Still, it’s helpful in a pinch and can even be viewed on the Blackberry’s browser.

Another problem is that HP has threatened to completely change the API so this tool, which is designed for HP SiteScope v 10.12, will probably completely break for newer versions. Oh, well.

This post shows some silly mistakes to avoid when doing a minor upgrade in version 11.

Ajax flot jquery Perl

Making Function Plots fun using Ajax while solving a real-world problem

I learned an awful lot from this exercise. I wanted to plot the trajectory of a foam basketball through the air. You know the kind of thing where you can vary the initial conditions to see what differences the results will produce. Finally, finally a good excuse to learn some Ajax. Ajax is a natural fit because you can work within the same web page and the feel is more interactive.

High level description
There’s so much here to describe I hardly know where to begin. I may never get through describing it all.

At the highest levels I had to learn some of the following:

  • php
  • Ajax
  • DOM
  • Javascript
  • jquery
  • flot
  • json

Perl and basic physics are not on the list – they are used but I already know those!

I basically only learned as much as I needed to accomplish the task. This saved me quite a bit of time as you can get bogged down for months in any single one of those topics above. I’m pretty good at “programming by analogy” and this really put those skills to the test because, as is usually the case, analogies were indeed present, but they weren’t very exact so I needed a scary amount of extrapolation from what samples were easily available.

The net result of all this? I think it’s pretty neat if I say so myself. This web page follows the trajectory of a small foam basketball from a given set of initial conditions. The trajectory is plotted. You tweak the initial conditions and a new trajectory is plotted on top of the old one so you can see the differences. Here’s a link to the application.

To be continued in great detail, hopefully…