Interactive Data Language (IDL) is a programming language for data analysis, visualization, and cross-platform application development. IDL combines tools for many types of projects, from "quick-look," interactive analysis and display to large-scale commercial programming projects.

NAS currently has IDL development licenses that allow 6 users to use the tool at the same time. Each license allows a single user to run multiple IDL sessions with the same session display simultaneously. Follow these steps to take advantage of this feature.

Before You Begin: Make sure you have set up SSH passthrough. In addition, read the articles listed in Setting Up Your Login for Improved Graphics Performance.

1. Use SSH to connect to a PFE.
2. Check the DISPLAY variable of the PFE, and launch multiple xterm sessions to run in the background. For example:

   pfe25% echo $DISPLAY
   pfe25:83.0
   
   pfe25% xterm&
   pfe25% xterm&
   pfe25% xterm&

3. In each xterm window, check the DISPLAY variable to confirm that it has the same number that was shown in the original window. Load an IDL module, then launch the idl command. For example:

   pfe25% echo $DISPLAY
   pfe25:83.0
   pfe25% module load idl/8.9
   pfe25% idl    
   IDL>

In the example above, a single user occupies only one IDL license rather than three licenses by ensuring that the IDL sessions are running in three separate xterm windows that all have the same DISPLAY number.

If all licenses are currently in use by other users, you will see a message similar to the following:

% Failed to acquire license. 

% A license is not available to run this product. 
Use the license administration utility to determine 
which licenses are available or activate an entitlement. 

You can run the following command to view how many licenses are currently in use: /u/scicon/tools/bin/check_licenses -i

If you cannot use IDL because all licenses are currently being used, try again at a later time. If you notice that multiple licenses are occupied by the same user, please contact the NAS Control Room at (800) 331-8737, (650) 604-4444, or by email at support@nas.nasa.gov.

For more information, see:

• NAS IDL License Policy
• IDL Documentation
• IDL Programming Language (Wikipedia)