The simplest way to tell edit/1 to use a specific editor is using the prolog flag editor, which can be set in the system or personal initialisation file. Two values have a special meaning. If the value starts with a $, it is taken as the name of an environment variable, e.g., $EDITOR, thus following the Unix convention to use this variable for selecting an editor. The value pce_emacs (default if XPCE is available) causes the internal Emacs clone to be used. Some examples:

If the editor is not known to SWI-Prolog, it will open the file, but not locate the editor to source-locations. To tell Prolog how to open a file and jump to a specified line, add a clause to prolog_edit:edit_command/2 . See the example below. See library/edit.pl for details.

:- multifile
        prolog_edit:edit_command/2.

edit_command(myedit, '%e --line=%d "%f"').

Editing the personal initialisation file

On Windows, using plwin.exe use Settings/User init file... from the menu. On first use it will ask you whether it should install the default profile. Confirm this and edit the result.

On systems using XPCE you can achieve the same from the SWI-Prolog help window opened with the ?- help. command.

For non-windows users, see PlInitialisation.md for how Prolog locates its customisation files.