In addition to the system library, SWI-Prolog searches app_config(lib) for library files. app_config is a SWI-Prolog search path (see file_search_path/2). The location this resolves to depends on the OS. We can find the locations using absolute_file_name/3. The call below finds the locations on a Linux system that implements the XDG file location standard.

?- absolute_file_name(app_config(lib), D, [solutions(all)]).
D = '/home/bob/.config/swi-prolog/lib' ;
D = '/etc/xdg/swi-prolog/lib'.

Files placed in these directories can be loading as normal libraries using e.g.,

?- use_module(library(mylib)).

In addition, we can add these libraries as autoload libraries using e.g.,

?- make_library_index('/home/bob/.config/swi-prolog/lib').

After this, any predicate exported from files in your personal library can be called immediately, i.e., without loading any libraries explicitly.

We advice to use this with care. It may be used to make the toplevel satisfy your daily requirements. One must be careful that the names of the modules, files and toplevel predicates are sufficiently unique to minimize the risk for conflicts.

See also

- PlInitialise.md