regexpdir(rootdir, expstr, recursive)

function dirlist = regexpdir(rootdir, expstr, recursive)
% REGEXPDIR Gives a directory listing based on a regular expression
%    REGEXPDIR(ROOTDIR, REGEXP) gives a directory listing of the directory 
%    ROOTDIR based on the pattern specified by the regular expression
%    REGEXP. 
% 
%    REGEXPDIR(ROOTDIR, REGEXP, RECURSIVE) By default REGEXPDIR traverses 
%    all subdirectories recursively. This behaviour can be controlled by
%    supplying the optional boolean RECURSIVE. Setting this to 'false' will
%    limit the function to the directory specified in ROOTDIR. 
% 
%    Example:
%     rootdir = 'C:\';
%     expstr = '^.*\.exe$';
%     dirlist = regexpdir(rootdir, expstr);
% 
%    The above example will return any EXE files on the C-drive. 
% 
%    By default REGEXPDIR searches case insensitive. To make it case
%    senstitive please specify it in the regular expression by adding 
%    '(?-i)' to it. Ommitting to specify the beginning '^' and ending '$'
%    of the regular expression may result in unexpected behaviour.
% 
%    Have a look at the source code for more information. For more 
%    info on this function and how to use it, bug reports, feature
%    requests, etc. feel free to contact the author.
% 
%    See also DIR, REGEXP, REGEXPTRANSLATE

%==========================================================================
% B.C. Hamans ([e-mail])                                 2007
%==========================================================================

% Check input arguments
error(nargchk(2, 3, nargin));
if ~exist('recursive','var'); recursive = true; end

% Check if the root directory contains a trailing file seperator or supply
rootdir = char(rootdir); 
if ~strcmp(rootdir(length(rootdir)), filesep); rootdir=[rootdir filesep]; end

% Remember initial starting directory when traversing. 
persistent basedir; if isempty(basedir); basedir = rootdir; end

% Traverse the structure
dirlist = cell({}); dirtree = dir(rootdir);
for h = find([dirtree.isdir]);
    if ~any(strcmp({'.','..'}, dirtree(h).name));
        if regexpi(strrep(fullfile(rootdir, dirtree(h).name, filesep), basedir, ''), expstr);
            dirlist = [dirlist; fullfile(rootdir, dirtree(h).name, filesep)];
        end
        if recursive;
            dirlist = [dirlist; regexpdir(fullfile(rootdir, dirtree(h).name, filesep), expstr, recursive)];
        end
    end
end
for i = find(~[dirtree.isdir]);
    if regexpi(strrep(fullfile(rootdir, dirtree(i).name), basedir, ''), expstr);
        dirlist = [dirlist; fullfile(rootdir, dirtree(i).name)];
    end
end

%==========================================================================
% Changelog:
% 03-09-2007 v1.00 (BCH)  Initial release
% 20-09-2007 v1.01 (BCH)  Proper solution for persistent variable 'basedir'
%==========================================================================