40.2 Waiting a Little While: sleep

• A quick-and-dirty reminder service when you don't have leave (48.5). This will print the message Time to go now.... in 10 minutes (600 seconds):

  ( ) & ;	% (sleep 600; echo Time to go now....) &

• You can't use at (40.3) and you have to run a job later (say, three hours):

  % (sleep 10800; someprog) &

• To watch a program (usually a shell script) that's running in the background and see what processes it runs:

  !!	% prog & [1] 12345 % sleep 5;ps PID TT STAT TIME COMMAND 18305 p4 S 0:01 -csh (csh) 18435 p4 S 0:00 /bin/sh prog 18437 p4 D 0:00 /bin/sort -r temp 18438 p4 R 0:00 ps % !!;!!;!!;!!;!! sleep 5; ps; sleep 5; ps; sleep 5; ps; sleep 5; ps; sleep 5; ps PID TT STAT TIME COMMAND ... ...5 seconds pass... PID TT STAT TIME COMMAND ...

• When you're running a series of commands that could swamp the computer, give it time to catch up. For instance, the mail (1.33) program starts background processes to deliver the mail. If you're sending a bunch of form letters, sleep five or ten seconds after each one:

  foreach	% foreach name (`cat people`) ? formltrprog $name | mail $name ? sleep 10 ? end

  Or, to send print jobs while you're at lunch - but give other people a chance to print between yours:

  % lp bigfile1;sleep 600;lp bigfile2;sleep 600;lp bigfile3