To schedule the execution of a command for x number seconds later (with csh(1)):
(sleep 1800; sh command_file >& errors)&
This incantation would wait a half hour before running the script command_file. (See the at(1) utility.)
To reiteratively run a command (with the csh(1)):
if (! -r zzz.rawdata) then
foreach i (ls *.rawdata)
awk -f collapse_data $i >> results
The scenario for a script such as this might be: a program currently running is taking longer than expected to process a series of files, and it would be nice to have another program start processing the files created by the first program as soon as it is finished (when zzz.rawdata is created). The script checks every five minutes for the file zzz.rawdata, when the file is found, then another portion processing is done courteously by sleeping for 70 seconds in between each awk job.