UUIDs (Universally Unique Identifier) or GUIDs (Globally Unique Identifier) are defined in this document: [http://www.webdav.org/specs/draft-leach-uuids-guids-01.txt]

Windows provides an API for generating GUIDs and some extensions make use of this, but I needed a pure-Tcl UUID generator.  So, I came up with this.  This proc, by no means, conforms to the standards discussed in the above document, but it does produce unique identifiers that are good enough for me. :)

 proc uuid {} {
     ## Try and get a string unique to this host.
     set str [info hostname]$::tcl_platform(machine)$::tcl_platform(os)
     binary scan $str h* hex

     set    uuid [format %2.2x [clock seconds]]
     append uuid -[string range [format %2.2x [clock clicks]] 0 3]
     append uuid -[string range [format %2.2x [clock clicks]] 2 5]
     append uuid -[string range [format %2.2x [clock clicks]] 4 end]
     append uuid -[string range $hex 0 11]

     return $uuid
 }