idlwave-shell-command-line-options

idlwave-shell-command-line-options is a variable defined in `idlwave.el'.
Its value is

nil

Documentation:
A list of command line options for calling the IDL program.
Since IDL is executed directly without going through a shell like /bin/sh,
this should be a list of strings like '("-rt=file" "-nw") with a separate
string for each argument. But you may also give a single string which
contains the options whitespace-separated. Emacs will be kind enough to
split it for you.

You can customize this variable.