crontab & stderr discovery

[Peter da Silva]

> > 1 0 * * * /bin/sh /usr/adm/script.sh 1>/usr/adm/script.log 2>&1
> > 1 0 * * * /usr/adm/script.sh 1>/usr/adm/script.log 2>&1
>   1 0 * * * exec /usr/adm/script.sh 1>/usr/adm/script.log 2>&1
> 
> I'll be amused if there are systems on which this fails!

On V7, not only will that fail, but so will the others. Does anyone know why
you can't run a shell script from crontab on V7? Is it just that cron doesn't
set up the right environment, or what?