SWI-Prolog -- file_search

file_search_path(+Alias, -Path)

Dynamic multifile hook predicate used to specify `path aliases'. This hook is called by absolute_file_name/3 to search files specified as Alias(Name), e.g., library(lists). This feature is best described using an example. Given the definition:

file_search_path(demo, '/usr/lib/prolog/demo').

the file specification demo(myfile) will be expanded to /usr/lib/prolog/demo/myfile. The second argument of file_search_path/2 may be another alias.

Below is the initial definition of the file search path. This path implies swi(<Path>) and refers to a file in the SWI-Prolog home directory. The alias foreign(<Path>) is intended for storing shared libraries (.so or .DLL files). See also use_foreign_library/1.

user:file_search_path(library, X) :-
        library_directory(X).
user:file_search_path(swi, Home) :-
        current_prolog_flag(home, Home).
user:file_search_path(foreign, swi(ArchLib)) :-
        current_prolog_flag(arch, Arch),
        atom_concat('lib/', Arch, ArchLib).
user:file_search_path(foreign, swi(lib)).
user:file_search_path(path, Dir) :-
        getenv('PATH', Path),
        (   current_prolog_flag(windows, true)
        ->  atomic_list_concat(Dirs, (;), Path)
        ;   atomic_list_concat(Dirs, :, Path)
        ),
        member(Dir, Dirs).

The file_search_path/2 expansion is used by all loading predicates as well as by absolute_file_name/[2,3].

The Prolog flag verbose_file_search can be set to true to help debugging Prolog's search for files.