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Transcript
CRON ( 8 ) CRON ( 8 ) N NA AM ME E cron – clock daemon S SY YN NO OP PS SIIS S auth/cron [-c] D DE ES SC CR RIIP PT TIIO ON N Cron executes commands at specified dates and times according to instructions in the files /cron/user/cron. It runs only on an authentication server. Option -c causes cron to create /cron/user and /cron/user/cron for the current user; it can be run from any Plan 9 machine. Blank lines and lines beginning with # in these files are ignored. Entries are lines with fields minute hour day month weekday host command Command is a string, which may contain spaces, that is passed to an rc(1) running on host for execution. The first five fields are integer patterns for minute 0– 59 hour 0– 23 day of month 1– 31 month of year 1– 12 day of week 0– 6; 0=Sunday The syntax for these patterns is time : | range : | | ’*’ range number number ’-’ number range ’,’ range Each number must be in the appropriate range. Hyphens specify inclusive ranges of valid times; commas specify lists of valid time ranges. Cron is not a reliable service. It skips commands if it cannot reach host within two minutes, or if the cron daemon is not running at the appropriate time. E EX XA AM MP PL LE ES S Here is the job that mails system news. % cat /cron/upas/cron # send system news 15 8-17, 21 *** helix /mail/lib/mailnews % S SE EE EA AL LS SO O con(1), rc(1) Page 423 Plan 9 January 20, 1993
