TweetFollow Us on Twitter

Apple Event CGIs

Volume Number: 15 (1999)
Issue Number: 8
Column Tag: Web Development

Apple Event Terminology for CGIs

by Chuck Shotton, BIAP Systems
Edited by Cal Simone, Technical Edit by Grant Neufeld

What changed in Mac OS 8.5?

A Little History

In 1993, MacHTTP was one of only 3 Web server products in existence. The other 2 were Unix-based servers from CERN in Switzerland and NCSA at the University of Illinois Urbana-Champaign. When they first appeared on the scene, all these servers could do is send back files of data. It quickly became apparent that to do really useful stuff, Web servers had to be able to interact with applications on the local machine.

Initially, the only external interface provided by URLs, HTTP, and HTML was an ability to specify search terms to some external program by putting those terms after a "?" in a URL. While it is rarely used today, many features besides free text searches were implemented with this mechanism. In order to implement search functions on the Mac, MacHTTP implemented a simple mechanism for invoking an AppleScript and passing some arguments to it.

In its first incarnation, the AppleScript source was loaded from disk, compiled by MacHTTP, and then executed each time a request for the "search engine" was received by the server. In order to pass arguments to the script, variable assignment statements were actually prepended to the AppleScript source read from disk, and compiled into the program. The output from this script was then returned to the HTTP client. Since this was in the days of HTTP 0.9, no HTTP header was required and most scripts just returned plain text or simple HTML documents that were generated on the fly.

As it turns out, this was one of the first applications that actually used AppleScript on the Mac in any significant way, but MacHTTP's performance when compiling and running AppleScripts for each request was painfully slow. It quickly became apparent that there had to be a better way to quickly load and execute external AppleScripts as well as stand-alone programs written in other languages. So a new AppleEvent was defined so that MacHTTP could launch external programs and pass the necessary parameters to the external application.

This was the genesis of the WWWOmegaSRCH, or "search" AppleEvent. It passed a single argument string (the data appearing after a "?" in a URL) to an external application and received a text response. While it increased performance by removing the overhead of recompiling an AppleScript each time a request was made, there was still the overhead of launching the application or script each time a request came in. In addition, it was about this time that the NCSA server implemented the first version of the CGI (Common Gateway Interface) standard.

In typical Unix fashion, CGIs were passed all of their arguments in Unix shell environment variables. Since the Mac OS had no similar function, implementing the CGI standard on a Mac required a different approach. Since MacHTTP already had a way to pass arguments to external applications, it made sense to simply extend the existing AppleEvent to pass all the parameters necessary to implement the CGI standard. Since older scripts and applications depended on the "search" event, a new event was created called "search document", or WWWOmegaSDOC.

Because AppleScript doesn't provide a convenient user-level mechanism for specifying your own English-like terminology for events that you create in AppleScripts, the familiar but totally unfriendly syntax of:

on «event WWWOmegaSDOC» ...

sprang into being. In order to list all the parameters passed to a script, an AppleScript CGI author had to carefully craft the event handler syntax, using the chevron syntax for the event and all of its parameters. While functional, it was not very readable and greatly complicated the learning curve for new users.

As the Mac CGI standard matured, the parameters passed to CGI applications from MacHTTP were extended to include approximately 15 different arguments. In order to make some sense out of the parameter list, Wayne Walrath of Acme Technologies created an Apple event terminology file that AppleScript CGI authors could install on their Macs that made the cryptic chevron syntax into something more human readable. While not widely distributed, this terminology file greatly improved the readability of AppleScripts.

With the advent of Mac OS 8, Apple began including a basic HTTP server for performing personal Web sharing. This server had the ability to send the same sorts of AppleEvents to external CGI applications provided by MacHTTP providedand other Mac servers like WebSTAR, Quid Pro Quo, and NetPresenz. However, it wasn't until the release of Mac OS 8.5 that the very widely used "SDOC" AppleEvent finally got officially-supported Apple event terminology as part of the core operating system.

What this means is that now AppleScript CGI authors can write CGI event handlers using simple English-like syntax without having to revert to the cryptic chevron syntax. In Mac OS 8.5, Apple included its version of the AppleEvent terminology as part of the "Standard Additions" file in the "Scripting Additions" folder in the OS 8.5 System Folder. In order to see the new syntax, users should use the Script Editor application to open the AppleEvent dictionary of the "Standard Additions" file.

The Handle CGI Event Syntax

  • handle CGI request: Sent to a script to process a Common Gateway Interface request
  • handle CGI request string - the path of the URL
  • [searching for string] - the data for the GET method or data after the '?' in a POST method
  • [with posted data string] - the POST arguments
  • [of content type string] - the MIME content type of POST arguments
  • [using access method string] - either 'GET' or 'POST'
  • [from address string] - the IP address of the entity making the request
  • [from user string] - the user name associated with the request
  • [using password string] - the password sent with the request
  • [with user info string] - additional information about the user, usually the email address
  • [from server string] - the name of the server application sending this request
  • [via port string] - the IP port number of the server
  • [executing by string] - the path to the script executing this CGI, in URL form
  • [referred by string] - the URL of the page the client used to link to the CGI
  • [from browser string] - the name of the client software
  • [using action string] - the path to the file or CGI
  • [of action type string] - either PREPROCESSOR, POSTPROCESSOR, CGI, or ACGI
  • [from client IP address string] - the Internet address of the client
  • [with full request string] - the full request as sent to the server
  • [with connection ID integer] - the ID of the connection from the server to the client
  • Result: web page - An HTML page resulting from the CGI execution

Format upgrade drawbacks

There are some drawbacks to Apple's addition of this AppleEvent terminology in Mac OS 8.5 that users need to be aware of. First, it can prevent existing, correctly written CGIs from being compiled. I found that every single one of my CGIs (based on the old MacHTTP CGI template scripts) failed to compile under the Mac OS 8.5 terminology, even though they compiled and ran fine under OS 8.1. This is because Apple chose to use relatively verbose and somewhat nonstandard terminology for their version of this event, causing several commonly used variable names to conflict with the Apple event keywords in the new terminology.

In order to correct this problem, you need to find all of the parameters in your old version of the SDOC event handler that have name conflicts with Apple's new terminology and rename those parameters. In my case, Apple had chosen to use the term "action" as a part of one of their keywords and I had used it as the name of one of my event's parameters. In order to clearly see which event parameters are causing problems, you may need to disable Apple's new terminology so you can easily examine your old script in the Script Editor. To do this:

  1. Quit the Script Editor
  2. Move the "Standard Additions" file out of the Scripting Additions folder temporarily, and reopen your old CGI in the Script Editor.

You'll then see the old chevron syntax for the SDOC event, and can easily compare your parameter names to the keywords found in Apple's dictionary entry for the CGI event.

Once you've changed your parameter names:

  1. Quit the editor, saving your script
  2. Reinstall the "Standard Additions" file,
  3. Reopen your CGI.

You should now have a script that compiles correctly and uses the new terminology.

One other problem that you should note stems from the fact that Apple implemented terminology for the SDOC event that is slightly out of date from the event commonly supported by the recent versions of Mac Web servers. Specifically, the "DIRE" parameter, which typically contains a string representing the Web server's current working directory, is not present in Apple's version of the SDOC event terminology. If your existing CGI script uses the DIRE parameter, it will still be available but it will revert to the old chevron syntax for that one parameter. If you need to write a new CGI that uses the DIRE parameter, you'll have to append a parameter to the end of Apple's parameter list that looks like:

given «class DIRE»: dir_path

An example script that uses the URL path, search arguments and server directory might look like:

Sample AppleScript using URL path, search args, and server directory

on handle CGI request inURLPath ¬ 
searching for inSearchArgs given «class DIRE»:dir_path
- build your HTTP header and response data, and return them...
end handle CGI request

Conclusion

For the most part, the addition of a standard terminology for the SDOC AppleEvent for AppleScript authors is a great benefit. If you have existing AppleScript CGIs, you'll have to be careful about the potential impact this new terminology can have on your CGIs. But with a small amount of modifications as described above, you can quickly take advantage of this new feature of Mac OS 8.5 and start writing much more readable, maintainable AppleScript CGIs.

Debugging an AppleScript CGI

Writing a CGI can be rewarding - and for a simple task, you can write the CGI in the Script Editor and, after a couple of tries, you should be able to get it to work.

The simple (limited) method:

  1. Write your CGI and save it as a stay-open script application ("CGI applet").
  2. Go to your browser and submit requests. Your web server software will send Apple event messages to your CGI applet.
  3. If the CGI doesn't work properly, you can examine the script in the Script Editor (or your favorite editor), searching for the problem command or commands, correcting the script, and saving again.

If you get stuck, you can insert dialog boxes, beeps, and writing stuff out to a text file. Any of these involves modifying your CGI, which means you aren't debugging the same CGI that you'll use for real - and you must take care to remove anything you placed in your script purely for debugging purposes.

While this method is straightforward, because of the indirect method of invoking the CGI handler in your script, it will be effective only if your CGI is short and simple.

But suppose something goes wrong? Or suppose your CGI is complex, involving several applications? How can you perfect it?

The deeper (cooler) method

If you have Main Event Software's Scripter, you have several tools available to debug your CGI "live". Getting a scripting environment beyond Apple's free Script Editor may cost a little bit, but how much is your time worth?

  • Drag the CGI applet onto the Live Edit application, which can be found in the Scripter Extras folder. The applet will quit if it's running. After several seconds, a dialog box will appear indicating that the CGI is ready for editing in Scripter.
  • Choose Observe in the Windows menu to open the Observe window. If you triple-click the first line of your CGI handler declaration (the line that starts with "on handle CGI request") and command-drag the line from your CGI's editing window to the Observe window, all your parameter values will appear in the Observe window whenever your CGI is called. You can also drag variable names from your script into the Observe window, useful to see their values change as you single step through your CGI.
  • If you want to see every line that executes in your script and every result, choose Log in the Windows menu to open the Log window.
  • Now you can go to your browser and submit requests. Your web server software will send Apple event messages to your CGI, but they will be diverted to Scripter. Each CGI request will appear in the Call Box window, where you can examine and modify it before calling the script and single-stepping through the handler. The handler's result will be displayed in the Call Box's result area, and will also be sent back to the web server.
  • The Live Edit application leaves behind another application called Reinstate xxxx, where xxxx is part or all of the name of your CGI applet (note that you can have several CGIs open for editing and debugging at the same time). When you're finished debugging, double-click the Reinstate application, and your revised CGI applet will be started and again made available directly to your web server.

Chuck Shotton (cshotton@biap.com) is the creator of MacHTTP, the first Mac webserver, which later evolved into WebSTAR.

 
AAPL
$111.78
Apple Inc.
-0.87
MSFT
$47.66
Microsoft Corpora
+0.14
GOOG
$516.35
Google Inc.
+5.25

MacTech Search:
Community Search:

Software Updates via MacUpdate

LibreOffice 4.3.5.2 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
CleanApp 5.0.0 Beta 5 - Application dein...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Monolingual 1.6.2 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... Read more
NetShade 6.1 - Browse privately using an...
NetShade is an Internet security tool that conceals your IP address on the web. NetShade routes your Web connection through either a public anonymous proxy server, or one of NetShade's own dedicated... Read more
calibre 2.13 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
Mellel 3.3.7 - Powerful word processor w...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
ScreenFlow 5.0.1 - Create screen recordi...
Save 10% with the exclusive MacUpdate coupon code: AFMacUpdate10 Buy now! ScreenFlow is powerful, easy-to-use screencasting software for the Mac. With ScreenFlow you can record the contents of your... Read more
Simon 4.0 - Monitor changes and crashes...
Simon monitors websites and alerts you of crashes and changes. Select pages to monitor, choose your alert options, and customize your settings. Simon does the rest. Keep a watchful eye on your... Read more
BBEdit 11.0.2 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
ExpanDrive 4.2.1 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more

Latest Forum Discussions

See All

Make your own Tribez Figures (and More)...
Make your own Tribez Figures (and More) with Toyze Posted by Jessica Fisher on December 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
So Many Holiday iOS Sales Oh My Goodness...
The holiday season is in full-swing, which means a whole lot of iOS apps and games are going on sale. A bunch already have, in fact. Naturally this means we’re putting together a hand-picked list of the best discounts and sales we can find in order... | Read more »
It’s Bird vs. Bird in the New PvP Mode f...
It’s Bird vs. Bird in the New PvP Mode for Angry Birds Epic Posted by Jessica Fisher on December 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Telltale Games and Mojang Announce Minec...
Telltale Games and Mojang Announce Minecraft: Story Mode – A Telltale Games Series Posted by Jessica Fisher on December 19th, 2014 [ permalink ] | Read more »
WarChest and Splash Damage Annouce Their...
WarChest and Splash Damage Annouce Their New Game: Tempo Posted by Jessica Fisher on December 19th, 2014 [ permalink ] WarChest Ltd and Splash Damage Ltd are teaming up again to work | Read more »
BulkyPix Celebrates its 6th Anniversary...
BulkyPix Celebrates its 6th Anniversary with a Bunch of Free Games Posted by Jessica Fisher on December 19th, 2014 [ permalink ] BulkyPix has | Read more »
Indulge in Japanese cuisine in Cooking F...
Indulge in Japanese cuisine in Cooking Fever’s new sushi-themed update Posted by Simon Reed on December 19th, 2014 [ permalink ] Lithuanian developer Nordcurrent has yet again updated its restaurant simulat | Read more »
Badland Daydream Level Pack Arrives to C...
Badland Daydream Level Pack Arrives to Celebrate 20 Million Downloads Posted by Ellis Spice on December 19th, 2014 [ permalink ] | Read more »
Far Cry 4, Assassin’s Creed Unity, Desti...
Far Cry 4, Assassin’s Creed Unity, Destiny, and Beyond – AppSpy Takes a Look at AAA Companion Apps Posted by Rob Rich on December 19th, 2014 [ permalink ] These day | Read more »
A Bunch of Halfbrick Games Are Going Fre...
A Bunch of Halfbrick Games Are Going Free for the Holidays Posted by Ellis Spice on December 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

The Apple Store offering free next-day shippi...
The Apple Store is now offering free next-day shipping on all in stock items if ordered before 12/23/14 at 10:00am PT. Local store pickup is also available within an hour of ordering for any in stock... Read more
It’s 1992 Again At Sony Pictures, Except For...
Techcrunch’s John Biggs interviewed a Sony Pictures Entertainment (SPE) employee, who quite understandably wished to remain anonymous, regarding post-hack conditions in SPE’s L.A office, explaining “... Read more
Holiday sales this weekend: MacBook Pros for...
 B&H Photo has new MacBook Pros on sale for up to $300 off MSRP as part of their Holiday pricing. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1699... Read more
Holiday sales this weekend: MacBook Airs for...
B&H Photo has 2014 MacBook Airs on sale for up to $120 off MSRP, for a limited time, for the Thanksgiving/Christmas Holiday shopping season. Shipping is free, and B&H charges NY sales tax... Read more
Holiday sales this weekend: iMacs for up to $...
B&H Photo has 21″ and 27″ iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only. B&H will also include a free copy of Parallels Desktop software: - 21″ 1.4GHz... Read more
Holiday sales this weekend: Mac minis availab...
B&H Photo has new 2014 Mac minis on sale for up to $80 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 1.4GHz Mac mini: $459 $40 off MSRP - 2.6GHz Mac mini: $629 $70 off MSRP... Read more
Holiday sales this weekend: Mac Pros for up t...
B&H Photo has Mac Pros on sale for up to $500 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2599, $400 off MSRP - 3.5GHz 6-core Mac Pro: $3499, $... Read more
Save up to $400 on MacBooks with Apple Certif...
The Apple Store has Apple Certified Refurbished 2014 MacBook Pros and MacBook Airs available for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Save up to $300 on Macs, $30 on iPads with Ap...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
iOS and Android OS Targeted by Man-in-the-Mid...
Cloud services security provider Akamai Technologies, Inc. has released, through the company’s Prolexic Security Engineering & Research Team (PLXsert), a new cybersecurity threat advisory. The... Read more

Jobs Board

*Apple* Store Leader Program (US) - Apple, I...
…Summary Learn and grow as you explore the art of leadership at the Apple Store. You'll master our retail business inside and out through training, hands-on experience, Read more
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.