timestrForFile.m

function [str] = timestrForFile( num )
% generate a timestamp for file
% this time stamp has eliminated charactors forbidden in filename

% num is a num for time stamp, now is the default.

if nargin==0
  num = now;
end

timestr = datestr(num);

timestr=  regexprep (timestr,':','-');
str =  regexprep (timestr,'\s','-');