file-write-date pathspec → date

pathspec — a pathname designator.

date — a universal time or nil.

Returns a universal time representing the time at which the file specified by pathspec was last written (or created), or returns nil if such a time cannot be determined.

 (with-open-file (s "noel.text" 
                    :direction :output :if-exists :error) 
   (format s "~&Dear Santa,~2%I was good this year.  ~ 
                Please leave lots of toys.~2%Love, Sue~ 
             ~2%attachments: milk, cookies~%") 
   (truename s)) 
→ #P"CUPID:/susan/noel.text" 
 (with-open-file (s "noel.text") 
   (file-write-date s)) 
→ 2902600800

The host computer’s file system.

An error of type file-error is signaled if pathspec is wild.

An error of type file-error is signaled if the file system cannot perform the requested operation.

Section 25.1.4.2 (Universal Time), Section 19.1.2 (Pathnames as Filenames)