Troubleshooting ION Script

If your ION Script application is not working as expected, start by checking the simple things first. Following is a list of some of the more common mistakes that may be causing problems with your application:

Web Server Problems

Before checking problems related to ION Script and IDL, make sure you are able to communicate with your Web server. For example, if you are using the Apache Web Server, you can enter a URL such as http://localhost or http://hostname, where hostname is the hostname or Windows machine name of your computer. If your Web server is properly configured, you should receive a page that says "If you can see this, it means that the installation of the Apache web server software on this system was successful." Consult your Web server documentation to find out how to test your Web server.

If You Are Using Microsoft IIS

Using Microsoft IIS, the .exe extension must be included in URLs that point to executables. You will need to use ion-p.exe instead of ion-p in any URLs in your HTML and ION Script pages, and in the location field of your browser when requesting a URL.

"Connection Failed" Errors

If you get the message "ION Script: Error: Connection Failed" when you attempt to load an ION Script page, check the following:

Does the page you are trying to load exist?

If you are using Windows Notepad as your text editor, make sure .txt was not appended to the end of your .ion file. When you save a file in Notepad, such as myfile.ion, Notepad may automatically append .txt to the end, as in myfile.ion.txt. To avoid this, enclose the file in double quotation marks in the Save As dialog before saving the file.

Does your URL point to the correct location of your cgi-bin directory?

Does your "ION Search Path" include the directory containing the page you are trying to load? The "ION Search Path" can be set on the "Files" tab of the ION Script Configuration utility (Windows) or in the "Files" section of the .ionsrc file (UNIX). Remember that you cannot use the "+" symbol in the ION Search Path to indicate that all subdirectories of the specified directory should be searched. Therefore, each directory you want to be searched must be explicitly specified. See ION Search Path for more information.

Do both the page you are trying to load and the directory containing the file have read permission?

If running ION Script on a UNIX Web server, does the case of the filename in the URL match the case of the actual filename?

If you are able to run ION Script applications directly from your Web server, but external users are not able to run ION Script applications, check the Image Server URL and ION Script Parser URL values on the URLs tab of the ION Script Configuration utility (Windows), or in the URLs section of the .ionsrc file (UNIX). You must specify your Web server's fully qualified domain name and path to the CGI executables directory for your Web server. For example, the "Image Server URL" should look something like this:

http://myhost.mydomain.com/cgi-bin/ion-i.exe

If, during the installation process, you left the field blank on the "Web Server Configuration" dialog in which you specify your Web server's fully qualified domain name, the installer will use your Windows machine name, or your hostname on UNIX.

Do you have an event named "page"? This is an illegal name for an event.

"Not Found" Errors

If you get an HTTP error informing you that the file or script you requested cannot be found, such as "HTTP Error 404," but the URL you are using appears to be correct, check the following:

The required executables may not have been copied to your Web server's cgi-bin directory. Make sure that the files ion-i.exe and ion-p.exe (Windows) or ion-i, ion-I, ion-p, and ion-P (UNIX) are in your Web server's cgi-bin directory. If not, copy them from the /ION63/ion_script/cgi-bin subdirectory of your ION Script installation to your Web server's cgi-bin directory. On UNIX, make sure that the files ion-i, ion-I, ion-p, and ion-P have execute permission.

Note that these executables would not be copied to the cgi-bin directory if, during the installation process, you left the field blank on the "Web Server Configuration" dialog in which you specify the CGI executables directory.

If you are using Microsoft IIS, the .exe extension must be included in URLs that point to executables. You will need to use ion-p.exe instead of ion-p in any URLs in your HTML and ION Script pages, and in the location field of your browser when requesting a URL.

"No Event or Page" Errors

If you get "Error: No event or page" when you use the Enter key to submit an ION_FORM containing a single text field, you need to associate an event with the text field by defining an event with the same name as the NAME attribute of the text field. For an example, see Forms Containing a Single Text Field.

Licensing Errors

If you get a page with an error message such as "License Error: ITT Visual Information Solutions license checkout failed", ION Script may not be properly licensed. View the licensing instructions in the Installing and Licensing IDL manual and make sure you have properly licensed ION.

ION Script Syntax Errors

Make sure all single tags use the proper syntax. Single tags are closed with />. Make sure you didn't mistakenly close a single tag using only >, or use tag-pair syntax for a single tag. ION Script will return an error message to inform you of a mismatched tag pair. For example, consider the following code:

<ION_BODY>  
   <ION_VARIABLE NAME="$A">  
</ION_BODY>

ION Script will return the following error:

Error: Mismatched tag pair: <ION_VARIABLE> ... </ION_BODY>

This error message indicates that you opened a tag called <ION_VARIABLE>, and ION Script found the next closing tag </ION_BODY>. This should alert you to the incorrect syntax for ION_VARIABLE (i.e., the proper way to close this tag is with /> rather than just >).

Make sure all tag pairs have both the opening and closing tag. For example, if you have an <ION_HEADER> tag, you must also have an </ION_HEADER> tag.

Check the case and spelling of your tags, attribute names, and system variables. Make sure you've used the exact case shown in the Tag Reference.

Make sure you have specified all the required attributes of a tag. In the syntax listings, attributes are required unless they are surrounded by square brackets.

Make sure all attribute values have been enclosed in double quotation marks. Remember to include both opening and closing quotation marks.

If you get the error "Illegal character ["] during parsing", make sure you have not included a carriage return between the double quotation marks that delimit the value of an ION Script attribute. For example, the following ION Script code is not allowed:

<ION_EVALUATE EXPR="$X +   
   $Y"/>

IDL Errors

Set the DEBUG attribute of the ION_DATA_OUT and ION_IMAGE tags to TRUE to cause a debugging file to be generated in the directory specified by the "ION Debug Location" setting on the "Debug" tab of the ION Script Configuration Utility (Windows) or in the "Debug" section of the .ionsrc file (UNIX). See DEBUG. This debugging file contains the exact code sent to IDL, as well as any errors reported by IDL.

Make sure your <IDL> blocks do not use IDL commands that cannot be entered at the command line such as a FOR loop or BEGIN statement.

Make sure you are not using any other IDL commands that are not allowed in ION Script. See IDL Tag Limitations.

If your <IDL> block contains a number (or an ION Script variable that begins with a number) enclosed in quotation marks, make sure you enclose the number or variable in single rather than double quotation marks. In IDL, a double quotation mark followed by a number denotes an octal constant. For example, the following code would cause a syntax error in IDL:

print, "1 Elm Street"

Instead, you would need to use

print, '1 Elm Street'

See Single vs. Double Quotation Marks for more information.

If you get an "Attempt to call undefined procedure/function" error, make sure the .pro or .sav file containing the procedure or function you are calling is located in a directory specified in the IDL Search Path. On UNIX, also make sure all directories in the IDL Search Path have the proper read permissions. Set the IDL Search Path on the "Files tab" of the ION Script Configuration utility (Windows) or in the "Files" section of the .ionsrc file (UNIX).

Variables

Check user-defined variables to make sure that each variable is used consistently with regard to case and spelling throughout the document. For example, make sure you didn't declare a variable as $A, and later assign a value to $a.

When checking the value of a boolean variable, such as in the statement
$A EQ TRUE, make sure you use either all uppercase or all lowercase letters for the boolean value. In other words, use only TRUE, true, FALSE, or false. Do not use True or False.

Make sure you didn't mistakenly declare a variable with a value that is of a different type than the specified TYPE. For example, if you assign a value of 4.99 to a variable declared as an INT, the value becomes 4.

When using a form variable in a numeric expression, make sure you declare a variable with the same value as the form variable and assign a numeric TYPE. See Using $Form Variables in Numeric Expressions.

If a value is being passed to an ION Script page in a URL, make sure you refer to this value as a $Form variable in the page to which the value is being passed. For example, assume you want to pass the parameter DATA with a value of 34 to the page mypage.ion with the following URL:

http://myserver/cgi-bin/ion-p?page=mypage.ion&DATA=34

In mypage.ion, in order to access the DATA parameter, you must refer to it as $Form.DATA, not $DATA.

Images Not Displaying

If your ION Script page contains an image from an <ION_IMAGE> tag, and a box is being displayed in place of the image you expect, check the following:

Make sure there are no IDL errors occurring in your <IDL> block. To do this, set the DEBUG="TRUE" in the ION_IMAGE tag to cause a debugging file to be generated in the directory specified by the ION Debug Location setting on the Debug tab of the ION Script Configuration utility (Windows) or in the Debug section of the .ionsrc file (UNIX). This debugging file contains the exact code sent to IDL, as well as any errors reported by IDL.

If your image is created from a .pro file, make sure the .pro file is in the IDL Search Path. The IDL Search Path can be set on the Files tab of the ION Script Configuration utility (Windows) or in the Files section of the .ionsrc file (UNIX).

Make sure you have specified the correct TYPE attribute for the ION_IMAGE tag. If the code in your IDL block uses IDL Object Graphics, the TYPE attribute must be set to OBJECT. If the code in your IDL block uses IDL Direct Graphics, the TYPE attribute must be set to DIRECT.