CRONTAB(5)                                             CRONTAB(5)

             crontab - tables for driving cron

             A crontab file contains instructions to the cron(8) daemon
             of the general form: ``run this command at  this  time  on
             this  date''.   Each  user has their own crontab, and com-
             mands in any given crontab will be executed  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 pound-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, comments
             are not allowed on the same line as  environment  variable

             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 subsequent 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.

             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.  HOME and SHELL may be overridden by set-
             tings in the crontab; LOGNAME may not.

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

             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.   If  MAILTO  is  defined but empty (MAILTO=""), no
             mail will be sent.  Otherwise mail is sent to the owner of
             the  crontab.   This  option  is  useful  if you decide on
             /bin/mail instead of /usr/lib/sendmail as your mailer when
             you  install  cron  --  /bin/mail doesn't do aliasing, and
             UUCP usually doesn't read its mail.

             The format of a cron command is very much the V7 standard,
             with  a number of upward-compatible extensions.  Each line
             has five time and date fields, followed by a user name  if
             this  is  the  system crontab file, followed by a command.
             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).
             Note that this means  that  non-existant  times,  such  as
             "missing  hours"  during daylight savings conversion, will
             never match, causing jobs scheduled  during  the  "missing
             times"  not  to  be run.  Similarly, times that occur more
             than once (again, during daylight savings conversion) will
             cause matching jobs to be run twice.

             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   0-31
                    month          0-12 (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

             Ranges of numbers are allowed.   Ranges  are  two  numbers
             separated  with  a  hyphen.  The specified range is inclu-
             sive.  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.  Fol-
             lowing 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 specify  command  execu-
             tion  every other hour (the alternative in the V7 standard
             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 partic-
             ular 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  cronfile.   Percent-signs  (%) in the command, unless
             escaped with backslash (\), will be changed  into  newline
             characters, and all data after the first % will be sent to
             the command as standard input.

             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 (ie, aren't *), the command will  be
             run when either field matches the current time.  For exam-
             ``30 4 1,15 * 5'' would cause a command to be run at  4:30
             am on the 1st and 15th of each month, plus every Friday.

             # use /bin/sh to run commands, no matter what /etc/passwd says
             # mail any output to `paul', no matter whose crontab this is
             # 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"

      SEE ALSO
             cron(8), crontab(1)

             When  specifying day of week, both day 0 and day 7 will be
             considered Sunday.  BSD and ATT  seem  to  disagree  about

             Lists  and  ranges  are  allowed  to  co-exist in the same
             field.  "1-3,7-9" would be rejected by ATT 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

             Names of months or days of the week can  be  specified  by

             Environment  variables  can be set in the crontab.  In BSD
             or ATT, the environment handed to child processes is basi-
             cally the one from /etc/rc.

             Command  output  is mailed to the crontab owner (BSD can't
             do this), can be mailed to a person other than the crontab
             owner  (SysV  can't do this), or the feature can be turned
             off and no mail will be sent at all (SysV  can't  do  this

             Paul Vixie <>

                               24 January 1994                        1

      -- is maintained by Ilya Sukhar