make-pathname

(make-pathname &key directory name type defaults)

Builds a pathname from its components: :directory (Common Lisp's list -- :absolute or :relative followed by one component per level -- or a directory namestring), :name (the file name without its type) and :type (the extension without its dot).

A directory component is a string or one of the keywords Common Lisp names the special levels by: :up / :back (..), :wild (*, one level) and :wild-inferiors (**, any number of levels). :wild is also what :name and :type take for their *:

That is the pathspec directory walks a whole subtree with and the from-wildcard translate-pathname rewrites against. :host, :device, :version and :case are accepted and dropped, as is any other keyword: a namestring models no such component, and a portability layer's call still works.

:defaults supplies every component the call did NOT, component-wise -- this is not a merge. A supplied component REPLACES the defaults' one instead of combining with it, and an explicitly supplied nil means "no component" rather than "take the default". That is Common Lisp's rule, so a supplied :directory does not nest under the defaults' directory:

Call	Result
`(make-pathname :name "b" :defaults "d/a.sql")`	`#P"d/b.sql"`
`(make-pathname :name "b" :type nil :defaults "d/a.sql")`	`#P"d/b"`
`(make-pathname :type "txt" :defaults "d/a.sql")`	`#P"d/a.txt"`
`(make-pathname :directory (list :relative "m") :name "b" :defaults "d/a.sql")`	`#P"m/b.sql"`
`(make-pathname :directory (list :absolute "u" "s") :name "b" :type "c")`	`#P"/u/s/b.c"`

Naming a sibling file is what this is for: pathname-name and pathname-type take a namestring apart by the same rule this puts one together by. To combine two paths instead of replacing components, use merge-pathnames.

Backend support

All four backends, as a real run-time function -- one definition in rontolisp source. On the compiled backends a call whose keywords and values are all literals is additionally folded to a literal pathname while the program is being built (which is what lets an asdf:system-relative-pathname result become a constant in the artifact); every other call -- a computed :defaults or :name, say -- runs the function. Both renderings implement the same rule.