passing global variable by reference?

From: Don S (dshesnicky_at_yahoo.com)
Date: 02/20/04 

Date: 20 Feb 2004 07:29:37 -0800

I'm trying to stick my frequently used subroutines into a Sysadmin.pm
module. Of course the first one I tried uses global variables and I
wondering if someone can guide me though referencing and derefrencing.

It's to walk a tree and call a subroutine on files/links/directories.
(I think I actually got the original code from the camel book.)
Anyway,
I also need to use global variables such as the level of directories
being descended but I take it I also want to "use strict" as a good
programming practice.

I've read in the camel book and it notes the \$ reference and
$$dereference but doesn't outline usage in subroutines.

I'm trying to call it like this:

                     vvvvvvv
 &tree_walk($top_dir,\$level,\&du_info,1,0,0);

the heart of the subroutine is (with errors):

 my($path,$$level,$sub,$d_flag,$f_flag,$l_flag) = @_;

 &tree_walk($newpath,$level,$sub,$d_flag,$f_flag,$l_flag); # ... go
recursive
 $level--;

and the actual subroutine is:

sub tree_walk{
   my($path,$$level,$sub,$d_flag,$f_flag,$l_flag) = @_;
   my($newpath,$entry,@entries);

# Get all objects in the directory

   opendir(DIR,"$path"); # open the
directory
   my(@entries) = readdir(DIR); # get all entries
   closedir(DIR); # close it

# Check all of the objects

   foreach $entry (@entries) {
      unless( $entry eq "." || $entry eq "..") { # filter always
         $newpath="$path/$entry"; # create full
path
         #-------- action on dirs, files, links ----------

         if( -d "$newpath" && $d_flag == 1) { # DIRECTORIES
            unless( -l "$newpath" ) { # ignore links
               &$sub($newpath,'d');
            }
         }

         #--------- recursively read directories ---------

         unless( -l "$newpath" ) { # stay away
from links
            if( -d $newpath ) { # if it is a
dir ...
               &tree_walk($newpath,$level,$sub,$d_flag,$f_flag,$l_flag);
# ... go recursive
               $level--;
            }
         }

      }
   }
}

Thanks,
Don

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