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 cron(1M)                                                           cron(1M)

 NAME    [Toc]    [Back]
      cron - timed-job execution daemon

 SYNOPSIS    [Toc]    [Back]

 DESCRIPTION    [Toc]    [Back]
      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

      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    [Toc]    [Back]
      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 11i Version 2: August 2003

 cron(1M)                                                           cron(1M)


    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    [Toc]    [Back]
      A history of all actions taken by cron is recorded in

 EXAMPLES    [Toc]    [Back]
      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 11i Version 2: August 2003

 cron(1M)                                                           cron(1M)

 WARNINGS    [Toc]    [Back]
      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    [Toc]    [Back]
    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

 AUTHOR    [Toc]    [Back]
      cron was developed by AT&T and HP.

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

 SEE ALSO    [Toc]    [Back]
      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.

      cron: SVID2, SVID3

 Hewlett-Packard Company            - 3 -   HP-UX 11i Version 2: August 2003
[ Back ]
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