ftw: Add `scandir'.

Suggested by Nala Ginrut <nalaginrut@gmail.com>.

* module/ice-9/ftw.scm (scandir): New procedure.
* test-suite/tests/ftw.test ("scandir"): New test prefix.
* doc/ref/misc-modules.texi (File Tree Walk): Document `scandir'.

doc/ref/misc-modules.texi

@@ -1249,6 +1249,18 @@ to `du --apparent-size' with GNU Coreutils.)"
 
 The alternative C-like functions are described below.
 
+@defun scandir name [select? [entry<?]]
+Return the list of the names of files contained in directory @var{name}
+that match predicate @var{select?} (by default, all files).  The
+returned list of file names is sorted according to @var{entry<?}, which
+defaults to @code{string-locale<?} such that file names are sorted in
+the locale's alphabetical order (@pxref{Text Collation}).
+
+This procedure is modeled after the C library function of the same name
+(@pxref{Scanning Directory Content,,, libc, GNU C Library Reference
+Manual}).
+@end defun
+
 @defun ftw startname proc ['hash-size n]
 Walk the file system tree descending from @var{startname}, calling
 @var{proc} for each file and directory.

module/ice-9/ftw.scm

@@ -193,9 +193,11 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 vlist)
   #:use-module (srfi srfi-1)
+  #:autoload   (ice-9 i18n)   (string-locale<?)
   #:export (ftw nftw
             file-system-fold
-            file-system-tree))
+            file-system-tree
+            scandir))
 
 (define (directory-files dir)
   (let ((dir-stream (opendir dir)))
@@ -505,4 +507,32 @@ children.  The optional STAT parameter defaults to `lstat'."
 
   (caar (file-system-fold enter?* leaf down up skip '(()) file-name stat)))
 
+(define* (scandir name #:optional (select? (const #t))
+                                  (entry<? string-locale<?))
+  "Return the list of the names of files contained in directory NAME
+that match predicate SELECT? (by default, all files.)  The returned list
+of file names is sorted according to ENTRY<?, which defaults to
+`string-locale<?'."
+  (define (enter? name stat result)
+    (and stat (string=? name name)))
+
+  (define (leaf name stat result)
+    (if (select? name)
+        (cons (basename name) result)
+        result))
+
+  (define (down name stat result)
+    (cons "." result))
+
+  (define (up name stat result)
+    (cons ".." result))
+
+  (define (skip name stat result)
+    ;; NAME itself is not readable.
+    #f)
+
+  (and=> (file-system-fold enter? leaf down up skip '() name stat)
+         (lambda (files)
+           (sort files entry<?))))
+
 ;;; ftw.scm ends here

test-suite/tests/ftw.test

@@ -166,3 +166,11 @@
                        expected)))
              (_ #f))
             children)))))
+
+(with-test-prefix "scandir"
+
+  (pass-if "test-suite"
+    (let ((select? (cut string-suffix? ".test" <>)))
+      (match (scandir (string-append %test-dir "/tests") select?)
+        (("." ".." "00-initial-env.test" (? select?) ...)
+         #t)))))