SWI-Prolog -- file_directory

Availability:built-in

file_directory_name(+File, -Directory)

Extracts the directory part of File. This predicate removes the longest match for the regular expression /*[^/]*/*$. If the result is empty it binds Directory to / if the first character of File is / and . otherwise. The behaviour is consistent with the POSIX dirname program.^{152Before
SWI-Prolog 7.7.13 trailing / where not
removed, translation /a/b/ into /a/b. Volker
Wysk pointed at this incorrect behaviour.}

See also directory_file_path/3 from library(filesex). The system ensures that for every valid Path using the Prolog (POSIX) directory separators, following is true on systems with a sound implementation of same_file/2.^{153On
some systems, Path and Path2 refer to the same
entry in the file system, but same_file/2
may fail.} See also prolog_to_os_filename/2.

        ...,
        file_directory_name(Path, Dir),
        file_base_name(Path, File),
        directory_file_path(Dir, File, Path2),
        same_file(Path, Path2).