here is one way to implement file globbing

[tantalum <sph@posteo.eu>]

im sure it is not the optimal way to do it, and currently it fails on 
file access errors and there might be bugs, but it has cool features and 
i just wanted to share.
filesystem globbing is the matching of paths that can include wildcard 
characters like asterisks.

the code implements the following:

filesystem-glob :: string -> (string ...)

   find files matching a file system path with optional wildcard 
characters.
   * matches zero or more of any character in a file name.
   ? matches one of any character in a file name.
   ** skips any sub directories to match the rest of the path. at the end 
of a path it is the same as **/.* including .*
   **n where n is an integer. like ** but skips directories at most n sub 
directories deep.
   example patterns
     a/b/*
     *.txt
     a/**/c/*.txt
     a/**
     **/*.txt
     a/**2/*

to list all files in a directory recursively: dir/**
and to list all pdf files in a directory recursively: dir/**/*.pdf

here is the code with reduced dependencies so that anybody with only 
guile should be able to run it:
http://files.sph.mn/s/computer/guile-fsg.scm

it is now part of sph-lib: 
https://github.com/sph-mn/sph-lib/blob/master/modules/sph/filesystem.scm

you can play around with it on the command-line by creating an 
executable file with content similar to this:

#!/usr/bin/guile
!#

(include "guile-fsg.scm")

(for-each (lambda (a) (display a) (newline))
   (filesystem-glob (car (cdr (program-arguments)))))


if this is in a file "mygl" then you can call it like "./mygl '/tmp/*'". 
paths in single quotes, otherwise the shell evaluates the wildcards.