For editing GDL / IDL .pro files on Linux you can of course use any Text Editor (gedit, vi) or the IDLDE, but the following could prove useful:
1. Kate
Kate Editor with GDL file
Kate is a text editor for the KDE desktop environment but looks just as good on a Gnome Desktop (Ubuntu default). Kate has built-in support for syntax highlighting .pro files. To install, search for Kate in the Ubuntu Software Centre, or at the command line use:
sudo apt-get install kate
Opening a .pro file in Kate should show your syntax highlighting and some auto-completion.
You can also have a split view with a terminal panel so you can run GDL commands.
Kate with GDL code and the GDL command prompt
2. Emacs & IDLWAVE
Emacs with IDLWAVE
The IDLWAVE website has some good instructions. First install emacs from the Ubuntu Software Center or at the command-line use:
sudo apt-get install emacs22-gtk
Next install IDLWAVE at the command line with the following commands:
wget http://idlwave.org/download/idlwave.tar.gz tar xzf idlwave.tar.gz cd idlwave-6.0/ make make install-all
After installing IDLWAVE create a file named .emacs (dot emacs) in your home directory with the following content:
;; This is only necessary if the default install directory is not on
;; your Emacs "load-path":
(setq load-path (cons "/usr/local/share/emacs/site-lisp" load-path))
(autoload 'idlwave-mode "idlwave" "IDLWAVE Mode" t)
(autoload 'idlwave-shell "idlw-shell" "IDLWAVE Shell" t)
(setq auto-mode-alist
(cons '("\.pro\'" . idlwave-mode) auto-mode-alist))
Open emacs (Applications > Accessories > Emacs 22) and notice the IDLWAVE menu. Notice the menu option for IDLWAVE > External > Start IDL shell. To get this to work you will need to create a symlink for the idl command pointing to the gdl program, as follows:
sudo ln -s /usr/bin/gdl /usr/bin/idl