title: File modification date on Unix/SAS
body: <p>Below is the guise of the DATA SET step. 
  I got files in a directory which start with a common prefix. </p>
  
  <p>For the sake of this debugging program, let's say the prefix is 'test'. </p>
  
  <p>So we got files like test_abc.txt, test_123.txt and so on.</p>
  
  <p>What we want to do is to extract the last modified time of each file.
  Since I am under Unix system, I use the following "foo pipe 'ls -o -g --full-time ...'" to get the time which we are interested in.</p>
  
  <p>In work.tempo, I wish to get a table with a list of filename(vname) and the corresponding modification date (mod_datec).</p>
  
  <p>Voilà le souci, je vous remercie!</p>
  
  <pre><code> %macro universe(directory, countryname, prefix);
  
    data work.tempo;
    length vname $256.;
    rc   = dopen(&amp;directory);
    vmax = dnum(rc);
  
    select("&amp;countryname");
     when ("France")
      do;
        do i = 1 to vmax;
         vname = dread(rc,i);
         if vname=:"&amp;prefix."
          then do;
  
           filename foo pipe "ls -g -o --full-time ~/&amp;prefix.*";
  
           data _null_;
           infile foo;
           input @15 mod_date $11.;
           if mod_date=" " then stop;
           mod_datec = scan(mod_date,1,"-")
                  ||scan(mod_date,2,"-")
                  ||scan(mod_date,3,"-");
           put mod_datec= ;
           run;
  
             /*I want to output mod_datec to work.tempo from here*/
  
          end;
        end;
      end;
  
  
  
    otherwise;        
    end;
  
    rc = dclose(rc);
    run;
  
   %mend;
  
   %universe(Earth, France, test);    
  </code></pre>