--- manifest
File{
        notify  => Exec["helloworld"]
}

file{"/tmp/trigger":
        content => "boom"
}

exec{"helloworld":
        command         => "date > /tmp/triggered",
        path            => "/bin",
        refreshonly     => true,
}


--- run
% puppet --verbose --debug test.pp
debug: File[/tmp/trigger]: Adding default for notify
debug: Creating default schedules
debug: Finishing transaction -605812208 with 0 changes
debug: //File[/tmp/trigger]/notify: subscribes to Exec[helloworld]
debug: //File[/tmp/trigger]: File does not exist
debug: //File[/tmp/trigger]/checksum: Initializing checksum hash
debug: //File[/tmp/trigger]: Changing content
debug: //File[/tmp/trigger]: 1 change(s)
debug: //File[/tmp/trigger]: Creating checksum {md5}65079b006e85a7e798abecb99e47c154
notice: //File[/tmp/trigger]/content: created file with contents {md5}65079b006e85a7e798abecb99e47c154
info: //File[/tmp/trigger]: Scheduling refresh of Exec[helloworld]
notice: //Exec[helloworld]: Triggering 'refresh' from 1 dependencies
debug: //Exec[helloworld]: Executing 'date > /tmp/triggered'
debug: Executing 'date > /tmp/triggered'
debug: Finishing transaction -606130078 with 1 changes
---

% cat /tmp/triggered
Wed Jul  2 21:33:27 BST 2008


--- run again this time no new alias so no need to exec
debug: File[/tmp/trigger]: Adding default for notify
debug: Creating default schedules
debug: Finishing transaction -605832688 with 0 changes
debug: //File[/tmp/trigger]/notify: subscribes to Exec[helloworld]
debug: //File[/tmp/trigger]/checksum: Initializing checksum hash
debug: //File[/tmp/trigger]: Creating checksum {md5}65079b006e85a7e798abecb99e47c154
debug: Finishing transaction -606150558 with 0 changes