Call IDL from Julia
Author BobPortmann
5 Stars
Updated Last
3 Years Ago
Started In
September 2016

IDL interface for the Julia language

Build Status

IDLCall is an interface to call IDL from the Julia language. Note that you must have a valid IDL license to use IDL from julia.


Within Julia, use the package manager:


IDLCall should find and load the IDL library automatically on Mac and Linux. It has not been tested on Windows so please file an issue if you use Windows and want to help make it work.

IDL can be called using either the RPC or Callable interface. On windows only the Callable interface is available. You can set an environmental variable JL_IDL_TYPE to RPC or CALLABLE to force the use of that interface. Alternatively you can set ENV["JL_IDL_TYPE] within julia before starting IDLCall. Note that by default IDLCall uses the RPC interface on Mac and Linux and Callable on Windows. The biggest difference between these is that:

  • Callable IDL runs in one program space and thus arrays can be shared between julia and IDL. In RPC all arrays are copied between processes. Note that I have run into issues with IDL loading DLM's while using Callable (e.g., NetCDF).

  • IDL RPC is not supported on windows

  • Callable is always managed by IDLCall while RPC can be managed by IDLCall or the user. By managed we mean that it is opened it when you load IDLCall and closed it when you close julia. To manage RPC yourself run idlrpc in a shell before starting IDLCall. This allows the idlrpc session to persist and julia can be restarted without killing the idlrpc process.


I recommend you start your code with

import IDLCall
idl = IDLCall

Then you can add a julia variable to the IDL process with

idl.put_var(x, "x")

and you can retrieve variable into julia using

x = idl.get_var("x")

You can run an arbitrary chunk of code in IDL using

idl.execute("any valid idl code")

Note that only primitive data types are supported at this time (e.g., structure variables are not supported yet).


You can drop into an IDL REPL by typing > at the julia prompt. Then you can type any valid IDL commands, including using continuation characters $ for multi-line commands. One experimental feature I have added is the use of %var will auto-magically import the julia variable var into the IDL process. This works at the IDL prompt or in strings passed into the execute function.


  • Add tests

  • Make more flexible to install on all platforms

  • Add more variable types to be transferred between julia and IDL.