There is a machine I work on which has an arrangement like this. (Although as has been pointed out, the cron script is not 'triggered'.)
The cron shell script runs each 5 minutes and just looks in an 'inbound' directory to see if there is anything there. If so it calls a second script (this one in Perl) which does some stuff with the file and then moves the file to a 'done' directory or to a 'failed' dir if it did not like the inbound file data . Simple and works.
No time to do clever stuff with signature.
