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 cron(1M)							    cron(1M)




 NAME
      cron - timed-job execution daemon

 SYNOPSIS
      /usr/sbin/cron

 DESCRIPTION
      cron executes commands at specified dates and times.  Regularly
      scheduled commands can be specified according to instructions placed
      in crontab files.	 Users can submit their own crontab files with a
      crontab command (see crontab(1)).	 Users can submit commands that are
      to be executed only once with an at or batch command.

      Since cron never exits, it should be executed only once.	This is best
      done by running cron from the initialization process with the startup
      script /sbin/init.d/cron (see init(1M)).

      cron only establishes a schedule for crontab files and at/batch
      command files during process initialization and when it is notified by
      at, batch, or crontab that a file has been added, deleted, or
      modified.

      When cron executes a job, the job's user and group IDs are set to
      those of the user who submitted the job.

    Spring and Autumn Time Transitions
      On the days of daylight savings (summer) time transition (in time
      zones and countries where daylight savings time applies), cron
      schedules commands differently from normal.

      In the following description, an ambiguous time refers to an hour and
      minute that occurs twice in the same day because of a daylight savings
      time transition (usually on a day during the Autumn season).  A
      nonexistent time refers to an hour and minute that does not occur
      because of a daylight savings time transition (usually on a day during
      the Spring season).  DST-shift refers to the offset that is applied to
      standard time to result in daylight savings time.	 This is normally
      one hour, but can be any combination of hours and minutes up to 23
      hours and 59 minutes (see tztab(4)).

      When a command is specified to run at an ambiguous time, the command
      is executed only once at the first occurrence of the ambiguous time.

      When a command is specified to run at a nonexistent time, the command
      is executed after the specified time by an amount of time equal to the
      DST-shift.  When such an adjustment would conflict with another time
      specified to run the command, the command is run only once rather than
      running the command twice at the same time.

      Commands that are scheduled to run during all hours (there is a * is
      in the hour field of the crontab entry) are scheduled without any



 Hewlett-Packard Company	    - 1 -   HP-UX Release 11i: November 2000






 cron(1M)							    cron(1M)




      adjustment.

 EXTERNAL INFLUENCES
    Environment Variables
      LANG determines the language in which messages are displayed.

      If LANG is not specified or is set to the empty string, it defaults to
      "C" (see lang(5)).  If any internationalization variable contains an
      invalid setting, all internationalization variables default to "C"
      (see environ(5)).

 DIAGNOSTICS
      A history of all actions taken by cron is recorded in
      /var/adm/cron/log.

 EXAMPLES
      The following examples assume that the time zone is MST7MDT.  In this
      time zone, the DST transition occurs one second before 2:00 a.m. and
      the DST-shift is 1 hour.

      Consider the following entries in a crontab file:

	   # Minute    Hour   MonthDay	Month  Weekday	 Command
	   # ----------------------------------------------------------
	       0       01	 *	 *	 *	 Job_1
	       0       02	 *	 *	 *	 Job_2
	       0       03	 *	 *	 *	 Job_3
	       0       04	 *	 *	 *	 Job_4
	       0       *	 *	 *	 *	 Job_hourly
	       0       2,3,4	 *	 *	 *	 Multiple_1
	       0       2,4	 *	 *	 *	 Multiple_2

      For the period of 1:00 a.m. to 4:00 a.m. on the days of DST
      transition, the results will be:

	       Job	    Times Run in Fall	Times Run in Spring
	       ____________________________________________________
	       Job_1		01:00 MDT	     01:00 MST
	       Job_2		02:00 MDT	     03:00 MDT
	       Job_3		03:00 MST	     03:00 MDT
	       Job_4		04:00 MST	     04:00 MDT
	       Job_hourly	01:00 MDT	     01:00 MST
				02:00 MDT
				02:00 MST
				03:00 MST	     03:00 MDT
				04:00 MST	     04:00 MDT
	       Multiple_1	02:00 MDT
				03:00 MST	     03:00 MDT
				04:00 MST	     04:00 MDT
	       Multiple_2	02:00 MDT	     03:00 MDT
				04:00 MST	     04:00 MDT



 Hewlett-Packard Company	    - 2 -   HP-UX Release 11i: November 2000






 cron(1M)							    cron(1M)




 WARNINGS
      In the Spring, when there is a nonexistent hour because of daylight
      savings time, a command that is scheduled to run multiple times during
      the nonexistent hour will only be run once.  For example, a command
      scheduled to run at 2:00 and 2:30 a.m. in the MST7MDT time zone will
      only run at 3:00 a.m.  The command that was scheduled at 2:30 a.m.
      will not be run at all, instead of running at 3:30 a.m.

 DEPENDENCIES
    HP Process Resource Manager
      If the optional HP Process Resource Management (PRM) software is
      installed and configured, jobs are launched in the initial process
      resource group of the user that scheduled the job.  The user's initial
      group is determined at the time the job is started, not when the job
      is scheduled.  If the user's initial group is not defined, the job
      runs in the user default group (PRMID=1).	 See prmconfig(1) for a
      description of how to configure HP PRM, and prmconf(4) for a
      description of how the user's initial process resource group is
      determined.

 AUTHOR
      cron was developed by AT&T and HP.

 FILES
      /var/adm/cron		    Main cron directory
      /var/spool/cron/atjobs	    Directory containing at and batch job
				    files
      /var/spool/cron/crontabs	    Directory containing crontab files
      /var/adm/cron/log		    Accounting information

 SEE ALSO
      at(1), crontab(1), sh(1), init(1M), queuedefs(4), tztab(4).

      HP Process Resource Manager: prmconfig(1), prmconf(4) in HP Process
      Resource Manager User's Guide.

 STANDARDS CONFORMANCE
      cron: SVID2, SVID3
















 Hewlett-Packard Company	    - 3 -   HP-UX Release 11i: November 2000