15 January 1990Paul VixieMany people have contributed to cron.  Many more than I can remember, in fact.Rich Salz and Carl Gutekunst were each of enormous help to me in V1; Carl forhelping me understand UNIX well enough to write it, and Rich for helping meget the features right.John Gilmore wrote me a wonderful review of V2, which took me a whole year toanswer even though it made me clean up some really awful things in the code.(According to John the most awful things are still in here, of course.)Paul Close made a suggestion which led to /etc/crond.pid and the mutex lockingon it.  Kevin Braunsdorf of Purdue made a suggestion that led to @reboot andits brothers and sisters; he also sent some diffs that lead cron toward compil-ability with System V, though without at(1) capabilities, this cron isn't goingto be that useful on System V.  Bob Alverson fixed a silly bug in the linenumber counting.  Brian Reid made suggestions which led to the run queue andthe source-file labelling in installed crontabs.Scott Narveson ported V2 to a Sequent, and sent in the most useful single batchof diffs I got from anybody.  Changes attributable to Scott are:	-> sendmail won't time out if the command is slow to generate output	-> day-of-week names aren't off by one anymore	-> crontab says the right thing if you do something you shouldn't do	-> crontab(5) man page is longer and more informative	-> misc changes related to the side effects of fclose()	-> Sequent "universe" support added (may also help on Pyramids)	-> null pw_shell is dealt with now; default is /bin/sh