Somewhat like the UNIX command '''du''' - returns number of bytes,
kilobytes, or megabytes in a directory hierarchy. '''Intentionally does NOT count links!!'''

 proc du { args } {
     
     switch -exact [ llength $args ] {
         0 {
           set dir .
           set switch -k
           }
         1 {
           set dir $args
           set switch -k
           }
         2 {
            set switch [ lindex $args 0 ]
            set dir [ lindex $args 1 ]
           }
   default {
           set msg "only one switch and one dir "
           append msg "currently supported"
           return -code error $msg
           }    
     }
  
     set switch [ string tolower $switch ]
     
     set -b 1
     set -k 1024
     set -m [ expr 1024*1024 ]
     
     set result [ list ]
     
     if { ! [ file isdirectory $dir ] } {
        set ary($dir,bytes) [ file size $dir ]
        set globpats [ list ]
     } else {
        set globpats $dir/*
     }
     
     while { [ llength $globpats ] } {
        foreach globpat $globpats {
           set cwd [ string trim $globpat */ ]
           set ary($cwd,bytes) 0
           set files [ glob -nocomplain $globpat ]
           set globpats [ list ]
           foreach file $files {
              if { ! [ catch {
                 file readlink $file
              } ] } {
                 continue
              }
              if { [ file isdirectory $file ] } {
                 lappend globpats $file/*
              } else {
                incr ary($cwd,bytes) [ file size $file ]
              }
           }
        }
     }
     
     set dirs [ array names ary ]
     
     # since the directories are arranged by nesting level
     # this can be optimised to not iterate in the inner
     # loop over directories already processed by the outer
     # loop.  I have no time right now...
     if { [ llength $dirs ] > 1 } {
        foreach dir $dirs {
           set dir [ lindex [ split $dir , ] 0 ]
           foreach Dir $dirs {
              set Dir [ lindex [ split $Dir , ] 0 ]
              if { [ string match $dir/* $Dir ] } {
                 incr ary($dir,bytes) $ary($Dir,bytes)
              }
           }
        }
     }

     foreach dir $dirs {
        set name [ lindex [ split $dir , ] 0 ]
        set size [ expr { $ary($dir) / [ set $switch ] } ]
        lappend retval [ list $name $size ]
     }
     # copyright 2002 by The LIGO Laboratory
     return $retval
 }
----
anyone that cares to may fill in the missing command line switches...
----