user:file_search_path/2 is undefined at startup,
but all callers first try a number of default file search paths, almost
as if user:file_search_path/2 had the following initial
clauses. Therefore, to expand file search paths, you should not call
user:file_search_path/2 directly, but instead call
absolute_file_name/[2,3].
See ref-lps-flg for more info on the Prolog flag host_type.
The system properties SP_APP_DIR and SP_RT_DIR expand
respectively to the absolute path of the directory that contains the
executable and the directory that contains the SICStus runtime. The
system property SP_TEMP_DIR expands to a directory suitable
for storing temporary files, it is particularly useful with the
open/4 option if_exists(generate_unique_name).
%% file_search_path/2 (virtual) initial clauses
file_search_path(library, '$SP_LIBRARY_DIR').
file_search_path(library, Path) :-
library_directory(Path).
file_search_path(system, Platform) :-
prolog_flag(host_type, Platform).
file_search_path(application, '$SP_APP_DIR').
file_search_path(runtime, '$SP_RT_DIR').
file_search_path(temp, '$SP_TEMP_DIR').
file_search_path(path, Path) :-
%% enumerate all directories in $PATH
...
The only default expansion for the library file search path is
the value of the system property SP_LIBRARY_DIR. However, you can
add expansions for library by adding clauses to
user:library_directory/1 (which is initially undefined). This
feature is mainly for compatibility with earlier releases. It is better
to add your own names for file search paths directly to
user:file_search_path/2 and not extend the file search path
library at all.
:- multifile user:library_directory/1.
user:library_directory('/home/joe/myprologcode/').
user:library_directory('/home/jane/project/code').