GizmoLA.com - Tech

Linux shell scripting: bad interpreter: No such file or directory

nospam@example.com (David Rolston) — Mon, 15 Sep 2008 16:22:39 -0700

This error pops up for a couple of reasons. At the top of the script there will probably be a line that looks like this:

#!/bin/sh

This is telling Linux that this script should be interpreted using the /bin/sh program. So your first step is to verify that program exists. I tend to use:

which sh

This will typically come back with a response like this:

/bin/sh

This is telling us that the path to the sh program is in fact /bin/sh, matching the path specified at the top of the script. Ok, so what gives? Well, it's possible that this script was made on an operating system that has line ending characters different than linux. This could have been on on a Mac or PC, or the file could have been converted when it was packaged. In this case, you get the relatively misleading bad interpreter: No such file or directory message, which is really trying to look for sh, although you don't get any indication of the fact.

So, how to fix? Read on.

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New Lula/Lampsig Coop Server

nospam@example.com (David Rolston) — Thu, 24 Jul 2008 10:55:09 -0700

So the UML Coop has finally after 3 years of talking about it, acquired a new server from Silicon Mechanics. Read the rest of the article for the complete specifications. We will be moving off User Mode Linux (UML) and on to OpenVZ. This change will allow us to accept some new members to the coop, so if you're interested drop me a line.

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AT+T Wireless XPress Mail Courier IMAP setup problem - Trash Folder?

nospam@example.com (David Rolston) — Sat, 12 Jul 2008 14:40:17 -0700

Having recently left a company that had Exchange, the removal of Goodlink from my Samsung Blackjack left the phone in a fairly broken state. I fixed this by doing a full reset (Turn on phone while holding Up Arrow) and choosing 1. This put things back in basic working order.

My efforts to use the built in email client to access my Courier IMap Email had never been successful, so I decided to explore AT+T's XPress Mail system. This consists of client software you install on the phone, and a desktop application that connects through AT+T's servers to give you access to your email remotely, and also can be used to give you access to files on your PC.

Upon install of the client you choose your mail server (in my case IMAP) and input the basic settings required by most IMAP client softare (Account name & Password, email address, the IMAP server, SMTP server, security settings, etc). I did notice an unusual configuration box asking for "Root Folder Path" which I left blank. Here's where the fun began.

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LAMP Tutorial Series originally published on PHPFreaks.com

nospam@example.com (David Rolston) — Tue, 27 May 2008 12:52:58 -0700

A few years ago I published a 3 part LAMP tutorial series entitled LAMP, MySQL/PHP Database Driven Websites on the well known php community website PHPFreaks.com. This series dealt with a slew of practical issues including how a LAMP server works, relational database design using MySQL, many to many tables, SQL inner and outer joins, practical PHP debugging, php documentation tools, basic PHP classes, css, interactive javascript & DHTML with a chooser widget, php HEREDOC and php basics like how to process forms and utilize GET and POST methods.

The series was fairly successful, (a 4.5 of 5 after hundreds of ratings), many pages of comments and questions, and page views to the 100k's+ although PHPFreaks auditing system was turned off at some point and stopped recording views.

Unfortunately, some years ago PHPFreaks.com suffered some fairly catastrophic issues with its publishing system. There were also some bugs, and the site was exploited with some XSS, and the admins simply decommissioned the majority of the site. My series was part of what disappeared. At that point, a couple of college Computer Science courses on web development had taken the series and integrated it into their curriculum, and the professor of one of these courses had converted it into a Word document, which I was able to download and convert to pdf.

I plan to write a compatible publishing addon for gizmola.com so that I can take the original markup and republish it here, but in the meantime, here is the series in pdf format. The conversion utility they used stripped out the original markup, and page breaks are gone, but the text, source code, and illustrations are all still there.

I also offer all the source code for parts 2 & 3 of the series. I'm not sure what happened to the source for part 1, however, it is all included inline in the tutorial. The LAMP, MySQL/PHP Database Driven Websites series is now available in pdf format. Click here.

Free Apple Mac style Dock with Windows Vista and RocketDock

nospam@example.com (David Rolston) — Sun, 10 Feb 2008 14:32:25 -0800

One of the distinctive features of Apple computers is a piece of software called "The Dock". The Dock is sort of an always there menu with big icons that spawn your most frequently used programs. Docks also can run small programs or docklets that can do things like display a clock or show you the weather. Docks also can be configured to display running programs that have been minimized in a mini window. You bring a running program to the front, or launch a program by hovering over the dock with your mouse, and clicking on the icon.

I suppose that people who don't know any better might think that this is something you can only get from Apple, but as it turns out there are docks for Linux and Windows. At home I have a Gateway computer running Windows Vista business, and I wanted to add a Dock. After a bit of hunting, I found some recommendations and settled upon RocketDock from Punk Labs. Punk Labs as it turns out is really a couple (he's a programmer, she's a designer) who go by the pseudonyms of PolyVector and Skunkie respectively. The about screen describes RocketDock tongue in cheek as a "peace offering" from the pair of self admitted Apple fans to Windows users everywhere.

The RocketDock website provides links to the various versions and a straightforward online manual. You get most of the features of the Apple Dock program, and it's very easy to work with. Once installed and running, the RocketDock appears at the top of the screen, with a set of default icons. Right click on the RocketDock and you get a menu that lets you adjust Dock settings. There are various themes that will style the look and feel of the RocketDock, and the RocketDock site offers an Extra's link with downloads to styles and docklet programs other people have contributed. While it's just a quibble with this otherwise great program, there's not much in the way of Docklets available, but I found it hard to resist adding on the simple analog style clock.
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Fun with Windows Vista and the Maxtor Shared Storage Drive

nospam@example.com (David Rolston) — Fri, 27 Jul 2007 23:48:49 -0700

I have a pair of 200 gigabyte Maxtor Shared Storage drives -- which are relatively inexpensive network storage drives that integrate with windows client machines. They come with an ethernet port you use to connect to a switch or hub on your home LAN, and will plug and play by negotiating an IP via DHCP. Maxtor (now owned by Seagate) provided a windows client that helps with finding and setting up the drives, since they advertise themselves as Workgroup peers that can be shared. I use the drives to store things like digital camera pictures and DVD's I've ripped in order to play them through my Tivo Series 2. They also come with some software that makes it easy to backup the My Documents area of our windows machines.

With Windows XP, the Shared Storage drives worked fairly reliably, but after I upgraded my Gateway desktop to Vista Business edition, I found myself unable to connect to the drives I'd mapped to it. Trying to mount them manually, I'd receive a login dialog. The name and password I use from my XP Pro based computer works fine, but on Vista the drive would reject the same credentials.

It took me a while to sit down and dig into the issue, and my first guess was that firmware might fix the problem. The Shared Storage drive predates Vista, so it wasn't a total surprise to me that authentication didn't work. The bundled web interface allows you to login with a browser, and administer the drive, setting up user accounts and mounting and unmounting USB devices you can connect to either of 2 provided USB ports. We have a printer attached.

After logging into the webserver, it displays a menu that includes the Firmware version -- mine was 1.2. A quick search of the Seagate site, and I found Maxtor offering version 2.6.2 firmware! The Advanced Settings | System Maintenance menu | System update menu provided a simple upload and update process that was completed in about 2 minutes. Despite the major point upgrade to the drive bios, I still was unable to login to the drive from Vista. What made this even more confusing is that I somehow had been able to successfully find the unit on the Windows network, authenticate to it and map a drive when I had first done the Vista upgrade. A bit of googling on the problem, and I discovered something surprising about the Maxtor unit I'd never suspected -- it is actually a linux box....
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Xen 3.0 Fedora Core, RHEL, Centos 4.x How-to

nospam@example.com (David Rolston) — Tue, 12 Jun 2007 00:28:03 -0700

I gave a talk on the use of Xen for web developers at Lampsig. It took me a while to get my notes transcribed, but here at last they are. This prescription has been used by me to install Xen successfully on a Fedora core 4 box, Centos 4.3 and 4.4 boxes, and should probably work on RHEL, assuming you can figure out how to get the packages you need.

I cover use of file backed file systems, and how to mount and edit them, as well as expanding a file based filesystem.

I have run gentoo and Centos guests I got from jailtime.org and have found them to be very stable. I even was able to use this on a 64 bit server, although I did have to build my own guest. Many people who have had trouble getting Xen to work reliably when using the packaged (rpm) versions of Xen may find this prescription fixes their problems.

Xen 3.0 Centos How-to

Install Xwindows and Gnome on Centos with Yum

nospam@example.com (David Rolston) — Sun, 20 May 2007 13:55:43 -0700

I recently had need to add XWindows to a Centos 4.x install that didn't have X or Gnome. I was doing this under VMware which added slightly to the degree of difficulty. As it turns out, using Yum makes this a very easy process, although you probably end up with some bloated packageware.

# yum groupinstall X Window System GNOME Desktop Environment

Pay close attention to the capitalization -- Yum is picky. "Gnome desktop environment" won't work, for example.

CAPTCHA busting -- A sucker born every minute

nospam@example.com (David Rolston) — Mon, 08 Jan 2007 22:50:14 -0800

I have a small phpBB2 forum attached to this site, that I used briefly to support some of my side projects. phpBB has had a checkered past in terms of security, having been the victim of many exploits. To be fair that's one of the costs of having been one of the first and most widely successful php based community projects. The number of phpBB deployments is staggering even to this day. With so many forums out there, spammers quickly figured out that if they could write a bot to create an account and auto post messages, they'd be able to spread their spam messages far and wide. I was getting so much spam, I ultimately disabled the ability of people to authenticate their own accounts, and despite this change, still see as many as ten new signups for the forum every day. Who would bother to sign up for an account they can't use? There had to be a way of determining the bots from the humans who wanted to post to my forum.

CAPTCHA, as the conventional wisdom of the day was concerned, would provide a useful deterrent to this annoyance -- bots arent' smart enough to decipher the captcha images and extract the right combination of numbers and letters depicted in the image, and type them back to into the form in order to unlock the account. Without the account, the spammers couldn't have their bots post their spam messages. While phpBB introduced a CAPTCHA capability relatively late in the game, it is now something you get out of the box, and there is at least one mod that improves on the quality of the CAPTCHA image, which is to say, makes it harder to read.

The problem is that CAPTCHA's are there to defeat dumb machines, but not dumb humans. And as the old saying goes, there's a sucker born every minute who is more than happy to help your local spammer defeat the CAPTCHA image on your site. How might you ask? Well, the scam works something like this: John Q. Sucker visits some site that informs him he's getting something for free -- it could be a free ipod, porn, or an xbox 360. All that is important is that this person believes they will be getting access to this free stuff once they register.

They visit the spammer's site, and are presented a CAPTCHA image in order to register, only, this image didn't come directly from the spammer's site -- it came from YOURS. The spammer writes a simple bot that goes to your site and hits the registration page. It takes the CAPTCHA image your site provided, and presents it to John Q. Sucker on the spammer's site.

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February LAMPsig presentation on SVG with Ajax demo

nospam@example.com (David Rolston) — Fri, 17 Feb 2006 08:45:08 -0800

I'll be talking about the Dynamic Scalable Vector Graphics (SVG) with Asynchronous Javascript and XML (Ajax) demo I created for the LAMPsig booth at the Southern California Linux expo 2006 (SCALE) conference that was held last weekend.

There were some excellent LAMP oriented discussions including Zend's Andi Gutmans himself, who talked about the PHP community project and PHP 6, then hung around for a while whilst myself and Chris Thompson peppered him with questions about MySQL's oop, its applicablility to the various framework projects underway. In short, Andi indicated that the PHP core team currently has no plans to add anything to the Oop capabilities of PHP 5, although I suppose that could change once the PHP Framework project matures. He indicated that the PHP Framework should be available in alpha or beta within the next few weeks.

Other LAMP hi-lights included Jim Winstead from MySQL AB who discussed new features in MySQL 5.x and provided some nice example code, and David Schecter from Sleepycat gave an entertaining talk that illustrated how integral berkely database is to Linux in general, and how its used by many major players to provide a high performance caching layer in front of oracle and mysql for websites like Yahoo.

Serendipity GeSHi Plugin update .05

nospam@example.com (David Rolston) — Sun, 13 Nov 2005 18:53:20 -0800

Give this a day and it should be in Spartacus and the Sourceforge Additional Plugins cvs branch.

-.05 release
- Updated GeSHi to latest release (1.0.7.4)
- This release includes some fixes, and new language files for:
applescript, D, diff output, DIV game language, DOS batch language, eiffel, freebasic, gml, Delphi Inno script, Matlab M language files, MySQL specific SQL, Objective CAML, Ruby, Scheme, SDLBasic, and VHDL: Very high speed integrated circuit HDL

Joomla PonyGallery tweak

nospam@example.com (David Rolston) — Sun, 13 Nov 2005 11:40:41 -0800

In the current release of the The Mambo/Joomla PonyGallery component, support for MamboJoe's Community Builder component is hardwired into the picture detail page. The Author name is a link to the Community Builder component. If you don't have that component installed, here is how you can remove the link.

You need to edit the PonyGallery script sub_viewdetails.php. This script is in the components/mod_ponygallery directory.

Find these lines:

echo "<tr class='sectiontableentry2'><td width='30%' valign='top'>"._PONYGALLERY_AUTHOR.":</td><td width='70%' valign='top'> <a href='index.php?option=com_comprofiler&task=userProfile&user=" . $imgownerid . "'>" . $imgowner
. "</a></td></tr>";

And replace them with this:

echo "<tr class='sectiontableentry2'><td width='30%' valign='top'>"._PONYGALLERY_AUTHOR.":</td><td width='70%' valign='top'>" . $imgowner
. "</td></tr>";

I'm fairly sure this will be a configuration item in the next release of PonyGallery Until then, if you aren't using CommunityBuilder, this will hold you over.

PHPlot, MySQL and the Dark Ages of Camelot

nospam@example.com (David Rolston) — Thu, 29 Sep 2005 16:46:15 -0700

The Dark Ages of Camelot (DAoC) is one of a number of Massive Multiplayer Online Role playing games (MMORPG) available for people who like those types of things. Mythic Entertainment, the company behind DAoC decided to offer an xml feed with various statistics about the game including the number of active players. From April 2002 to July 2005 I used a cron job to query the xml feed once every 5 minutes, parse the results and store the statistics in a database table.

I made a graph of these statistics available on a fan site I operated. The graph used the open source PHPlot graphing class in order to draw a line graph charting the number of players playing the game by hour for a 24 hour period. Visitors to the site would see the line graph shown here, plotting the number of players per hour against a second line showing the day's average. Like many PHP graphing libraries, PHPlot assumes that you have the GD library installed and available to PHP on order for the graphs to work.

This was one of my early experiments with PHP, and illustrated its power and flexibility. Now that the site where the graph appeared is no longer online, I figured I would provide the code, and a small subset of the database, for people interested in how to program with PHPlot. At the time I created this code, PHPlot didn't have much documentation and required some trial and error experimentation. Of course, since then (several years now) PHPlot has been improved, and should definately be considered if you want graphing in your application. Because I don't want to spend time debugging old obsolete code, I've provided the library I used in the download along with the graph script. It would probably work with the latest release, but I don't have time to test it. You can download my example database, version of PHPlot and script here. The database contains one months data, so you can play with the script and explore the class.

Read on for some brief instructions and an explanation of the code.
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Joomla (Mambo) Core ERD diagrams

nospam@example.com (David Rolston) — Fri, 23 Sep 2005 13:28:46 -0700

I have a small project that involves an implementation of Joomla (a fork of the popular PHP/Mysql based content management system Mambo). I started with Mambo and during the time I was configuring the site, the core developers of Mambo left to create the Joomla project. The reasons for this are discussed on their OpenSourceMatters website.

Suffice it to say, I find an Entity Relationships diagram to be very helpful in understanding the architecture of a database driven application like Joomla. There wasn't one available, so I decided to reverse engineer the database, and created these diagrams, which break the core database down into a few functional areas.

User and Security Subsystem

Backend (modularity and extensibility) Subsystem

Content and Presentation Subsystem

Banners

Logging

RegEx and the Mod_rewrite reference sheet

nospam@example.com (David Rolston) — Fri, 09 Sep 2005 13:12:11 -0700

Dave Child, a Brighton UK based Web developer offers a series of free Reference/Cheat sheets that I think most web developers will find of value. He obviously invested a lot of time and effort into them and it shows. He's created free cheat sheets for MySQL, Javascript, PHP, RGB colors and the subject today's Gizmola.com entry, Apache mod_rewrite. If you've used Apache there's a good chance you've heard of mod_rewrite, although you might not understand what it can do for you. Lately, a lot of PHP scripts are including functionality that will create mod_rewrite rules and add them to a .htaccess file to support "SEO friendly" url's. Serendipity, which runs my blog, and the popular PHP Content Management System Mambo/Joomla are just two examples of packages that can do this for you.

For example, if your script uses a parameter like this: http://www.yoursite.com/home.php?id=5

A mod rewrite rule can allow users to use: http://www.yoursite.com/home/5/

Many search engines seem to penalize sites that use URL parameters, and are more likely to index and value the non-parameter version. Of course, that's not all that mod_rewrite can do. Many people use it for its ability to offer at least a layer of Hotlink protection, or to handle things like forwarding visitors from obsolete pages that might exist in a search engine to the new ones.

Using and understanding the black magic of mod_rewrite requires a basic understanding of Regular Expressions or as they are typically known: RegEx. If you're new to RegEx, think of them as wildcards on steroids. The October Lampsig meeting will present RegEx basics, and if you're in Los Angeles, definately try and attend the presentation, which will be given by Peter Benjamin. Check out Dave Child's succint reference for this powerful module whether or not you plan to attend Pete's presentation.

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