crontab


DESCRIPTION
       A  crontab file contains instructions to the cron(8) daemon of the gen-
       eral form: ``run this command at this time on this date''.   Each  user
       has  their  own crontab, and commands in any given crontab will be exe-
       cuted as the user who owns the crontab.  Uucp  and  News  will  usually
       have  their  own  crontabs, eliminating the need for explicitly running
       su(1) as part of a cron command.

       Blank lines and leading spaces and tabs are ignored.  Lines whose first
       non-space  character  is a hash-sign (#) are comments, and are ignored.
       Note that comments are not allowed on the same line as  cron  commands,
       since  they  will  be taken to be part of the command.  Similarly, com-
       ments are not allowed on the same line  as  environment  variable  set-
       tings.

       An  active line in a crontab will be either an environment setting or a
       cron command.  An environment setting is of the form,

           name = value

       where the spaces around the equal-sign (=) are optional, and any subse-
       quent non-leading spaces in value will be part of the value assigned to
       name.  The value string may be placed in quotes (single or double,  but
       matching)  to  preserve leading or trailing blanks. The value string is
       not parsed for environmental substitutions, thus lines like

           PATH = $HOME/bin:$PATH

       will not work as you might expect.

       Several environment variables are set up automatically by  the  cron(8)
       daemon.  SHELL is set to /bin/sh, and LOGNAME and HOME are set from the
       /etc/passwd  line  of   the   crontab's   owner.   PATH   is   set   to
       "/usr/bin:/bin".   HOME,  SHELL, and PATH may be overridden by settings
       in the crontab; LOGNAME is the user that the job is running  from,  and
       may not be changed.

       (Another  note:  the  LOGNAME  variable is sometimes called USER on BSD
       systems...  on these systems, USER will be set also.)

       In addition to LOGNAME, HOME, and SHELL, cron(8) will look at MAILTO if
       it  has  any  reason  to  send  mail as a result of running commands in
       ``this'' crontab.  If MAILTO is defined (and non-empty), mail  is  sent
       to the user so named.  MAILTO may also be used to direct mail to multi-
       ple recipients by separating recipient users with a comma. If MAILTO is
       defined but empty (MAILTO=""), no mail will be sent.  Otherwise mail is
       sent to the owner of the crontab.

       On the Debian GNU/Linux system, cron supports the pam_env  module,  and
       loads  the  environment  specified  by  /etc/environment and /etc/secu-
       rity/pam_env.conf.  However, the PAM setting do NOT override  the  set-
       tings described above nor any settings in the crontab file itself. Note
       in particular that if you want a PATH other than  "/usr/bin:/bin",  you
       ber  of upward-compatible extensions.  Each line has five time and date
       fields, followed by a command, followed by a newline character  ('\n').
       The system crontab (/etc/crontab) uses the same format, except that the
       username for the command is specified after the time  and  date  fields
       and before the command. The fields may be separated by spaces or tabs.

       Commands  are  executed  by cron(8) when the minute, hour, and month of
       year fields match the current time, and when at least one  of  the  two
       day  fields  (day of month, or day of week) match the current time (see
       ``Note'' below).  cron(8) examines cron entries once every minute.  The
       time and date fields are:

              field          allowed values
              -----          --------------
              minute         0-59
              hour           0-23
              day of month   1-31
              month          1-12 (or names, see below)
              day of week    0-7 (0 or 7 is Sun, or use names)

       A field may be an asterisk (*), which always stands for ``first-last''.

       Ranges of numbers are allowed.  Ranges are two numbers separated with a
       hyphen.  The specified range is inclusive.  For example,  8-11  for  an
       ``hours'' entry specifies execution at hours 8, 9, 10 and 11.

       Lists are allowed.  A list is a set of numbers (or ranges) separated by
       commas.  Examples: ``1,2,5,9'', ``0-4,8-12''.

       Step values can be used in conjunction with ranges.  Following a  range
       with  ``/<number>''  specifies  skips of the number's value through the
       range.  For example, ``0-23/2'' can be used in the hours field to spec-
       ify command execution every other hour (the alternative in the V7 stan-
       dard is ``0,2,4,6,8,10,12,14,16,18,20,22'').  Steps are also  permitted
       after  an asterisk, so if you want to say ``every two hours'', just use
       ``*/2''.

       Names can also be used for the ``month'' and ``day  of  week''  fields.
       Use  the  first  three  letters  of  the  particular day or month (case
       doesn't matter).  Ranges or lists of names are not allowed.

       The ``sixth'' field (the rest of the line) specifies the command to  be
       run.   The  entire  command  portion  of the line, up to a newline or %
       character, will be executed by /bin/sh or by the shell specified in the
       SHELL  variable of the crontab file.  Percent-signs (%) in the command,
       unless escaped with backslash (\), will be changed into newline charac-
       ters,  and  all  data  after the first % will be sent to the command as
       standard input. There is no way to split a  single  command  line  onto
       multiple lines, like the shell's trailing "\".

       Note:  The  day of a command's execution can be specified by two fields
       -- day of month, and day of week.  If both fields are restricted (i.e.,
       aren't  *),  the command will be run when either field matches the cur-
       rent time.  For example,
              @weekly        Run once a week, "0 0 * * 0".
              @daily         Run once a day, "0 0 * * *".
              @midnight      (same as @daily)
              @hourly        Run once an hour, "0 * * * *".

EXAMPLE CRON FILE
       # use /bin/bash to run commands, instead of the default /bin/sh
       SHELL=/bin/bash
       # mail any output to `paul', no matter whose crontab this is
       MAILTO=paul
       #
       # run five minutes after midnight, every day
       5 0 * * *       $HOME/bin/daily.job >> $HOME/tmp/out 2>&1
       # run at 2:15pm on the first of every month -- output mailed to paul
       15 14 1 * *     $HOME/bin/monthly
       # run at 10 pm on weekdays, annoy Joe
       0 22 * * 1-5    mail -s "It's 10pm" joe%Joe,%%Where are your kids?%
       23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"
       5 4 * * sun     echo "run at 5 after 4 every sunday"

EXAMPLE SYSTEM CRON FILE
       This has the username field, as used by /etc/crontab.
       # /etc/crontab: system-wide crontab
       # Unlike any other crontab you don't have to run the `crontab'
       # command to install the new version when you edit this file
       # and files in /etc/cron.d. These files also have username fields,
       # that none of other the crontabs do.

       SHELL=/bin/sh
       PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

       # m h dom mon dow user    command
       42 6 * * *        root    run-parts --report /etc/cron.daily
       47 6 * * 7        root    run-parts --report /etc/cron.weekly
       52 6 1 * *        root    run-parts --report /etc/cron.monthly
       #
       # Removed invocation of anacron, as this is now handled by a
       # /etc/cron.d file

SEE ALSO
       cron(8), crontab(1)

EXTENSIONS
       When specifying day of week, both day 0 and day 7  will  be  considered
       Sunday.  BSD and AT&T seem to disagree about this.

       Lists  and ranges are allowed to co-exist in the same field.  "1-3,7-9"
       would be rejected by AT&T or BSD cron -- they  want  to  see  "1-3"  or
       "7,8,9" ONLY.

       Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".

       Months or days of the week can be specified by name.

AUTHOR
       Paul Vixie <paul@vix.com>



4th Berkeley Distribution       24 January 1994                     CRONTAB(5)
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