file-name-extension

diff --git a/lispref/files.texi b/lispref/files.texi
index e27ab8f81d2c1f1bd9e48f0a83390a9b3b987c67..02c863421f97f8e4a064fc84a558dfec90c4ef1a 100644 (file)
--- a/lispref/files.texi
+++ b/lispref/files.texi
@@ -1526,6 +1526,14 @@ value of @code{?/}.
 @end defvar
 @end ignore
 
+@defun file-name-extension filename &optional period
+This function returns @var{filename}'s final ``extension,'' if any,
+after applying @code{file-name-sans-versions} to remove any
+version/backup part.  If @var{period} is non-nil, then the returned
+value includes the period that delimits the extension, and if
+@var{filename} has no extension, the value is @code{""}.
+@end defun
+
 @node Directory Names
 @comment  node-name,  next,  previous,  up
 @subsection Directory Names