After installing ENVI 5.4 and then installing IDL 8.6 on the same machine, the command "e=envi()" results in "% Syntax error."

Question:  

I installed ENVI 5.4 and then separately installed IDL 8.6 to the same machine.  I then started an IDL session from the IDL installation and tried to start ENVI by issuing the following command at the IDL> prompt: e = envi(). The result was "% Syntax error." What is the problem?

Answer: 

The behavior described is expected when attempting to start ENVI 5.4 from a separate IDL 8.6 installation. 

Note that it is not necessary to install both IDL 8.6 and ENVI 5.4 to a machine in order to use ENVI+IDL. Beginning with ENVI 5.4, the ENVI product installer will install its own copy of IDL 8.6 beneath the main "envi54" product directory.  For example, on Windows this location would be:

C:\Program Files\Harris\ENVI54\IDL86

If you were to install IDL 8.6 separately, the directory would be:

C:\Program Files\Harris\IDL86

The solution to this problem then is to start your IDL session from the IDL product that is included under the ENVI 5.4 installation before issuing the command "e = envi()".

Reviewed by JU (12/7/2016)