: #!/usr/bin/tcl
: # Change this to what you want to be executed, \$IP being the new IP
: set Execute "echo \$IP | mail joo@schmoo"
: 
: set NewIp "0.0.0.0"
: set iface 0
: while {1} {
:   set meep [split [exec /sbin/ifconfig] \n]
:   foreach mp $meep {
:     if {[string range [lindex $mp 0] 0 2]=="ppp"} { set iface 1 }
:     if {[lindex $mp 0]=="inet" && $iface} {
:       set word [split [lindex [split [lindex $mp 1] :] 1] .]
:       set OldIp $NewIp
:       set NewIp "[lindex [split [lindex $mp 1] :] 1]"
:       set IP $NewIp
:       if {$OldIp != $NewIp} {
:         catch { system [subst $Execute] }
:       }
:       set iface 0
:     }
:   }
:   sleep 60
: }