[PD] tabcycle equivalent in pd?, shell/OS commands from within pd?

[Matthias Blau]

Hi all,

two questions:
1.) I don't seem to find a direct equivalent to jmax's tabcycle~ in pd. 
I could probably use tabplay~ but I haven't figured out how to trigger 
it continuously.
2.) I would love to be able to issue shell commands from within pd, e.g. 
for doing off-line computations with recorded material, or for doing 
file transactions and the like. Is this something which is already 
implemented in some way?

Thanks for any help,
Matthias