crontab

PURPOSE

     Submits a schedule of commands to cron.

SYNOPSIS
     crontab [ file ]
     crontab -l
     crontab -r


DESCRIPTION

     The  crontab  command  copies   the  specified  file,  or
     standard  input if  you do  not  specify a  file, into  a
     directory that holds all  users' crontab files.  The cron
     command runs  commands according  to the  instructions in
     these crontab files.   It then mails you  the output from
     standard output  and standard  error for  these commands,
     unless you  redirect standard  output or  standard error.
     When entries  are made  to a  crontab file,  all previous
     entries are erased.

     You may use  crontab if your logname appears  in the file
     /usr/lib/cron/cron.allow.  If  that file does  not exist,
     crontab checks the file /usr/lib/cron/cron.deny to deter-
     mine  if you  should  be denied  access  to crontab.   If
     neither file exists, you can submit a job only if you are
     operating with superuser authority.  The allow/deny files
     contain one user name per line.

     Notes:

     1.  If your  login ID  is associated  with more  than one
         login name,  crontab uses  the first login  name that
         appears in the /etc/passwd  file, regardless of which
         login name you might actually be using.

     2.  If  cron.allow exists,  the superuser's  logname must
         appear there for the superuser  to be able to use the
         command.

     Each  crontab file  entry  consists of  a  line with  six
     fields,  separated  by  spaces and  tabs,  that  contain,
     respectively:

     1.  The minute (0-59)
     2.  The hour (0-23)
     3.  The day of the month (1-31)
     4.  The month of the year (1-12)
     5.  The day of the week (0-6 for Sunday-Saturday)
     6.  The shell command.

     Each of these fields can contain:

     o   A number in the specified range
     o   Two  numbers  separated by  a  minus  to indicate  an
         inclusive range
     o   A list of numbers  separated by commas, which selects
         all numbers in the list
     o   An asterisk, meaning all legal values.

     Note that  the specification of  days may be made  by two
     fields (day  of the month and  day of the week).   If you
     specify both as a list  of elements, both are adhered to.
     For example the following entry:

       0 0 1,15 * 1 command

     would run command on the first and fifteenth days of each
     month, as well as every  Monday.  To specify days by only
     one field, the other field should contain an "*".

     The  cron command  runs the  command named  in the  sixth
     field at  the selected date  and time.  If you  include a
     "%" (percent sign) in the sixth field, cron treats every-
     thing  that precedes  it  as the  command invocation  and
     makes all  that follows  it available to  standard input,
     unless  you escape  or quote  the percent  sign ("\%"  or
     ""%"").

     Note: The shell runs  only the first line  of the command
     field (up to a "%" or  end of line).  All other lines are
     made available to the command as standard input.

     The  cron  command invokes  a  subshell  from your  $HOME
     directory.  This means that it will not run your .profile
     file.  If you schedule a command  to run when you are not
     logged in and you want  to have commands in your .profile
     run, you must explicitly do so in the crontab file.  (For
     a more detailed discussion of  how sh can be invoked, see
     "sh").

     cron  supplies a  default  environment  for every  shell,
     defining  HOME,  LOGNAME,  SHELL (="/bin/sh"),  and  PATH
     (=":/bin:/usr/bin").

FLAGS

     -l    Lists your crontab file.
     -r    Removes your  crontab file from the  crontab direc-
           tory.

EXAMPLES

     The following examples show valid crontab file entries.

     1.  To write  the time to  the console every hour  on the
         hour:

           0 * * * * echo The hour is `date`. >/dev/console

         This  example uses  command  substitution.  For  more
         information, see "Command Substitution."
     2.  To run calendar at 6:30 a.m. every Monday, Wednesday,
         and Friday:

           30 6 * * 1,3,5 /usr/bin/calendar -

     3.  To define text for the standard input to a command:

           0 16 10-31 12 5 /etc/wall%HAPPY HOLIDAYS!%Remember to turn in your time card.

         This writes a message to  all users logged in at 4:00
         p.m. each Friday between December 10th and 31st.

         The text following the "%" (percent sign) defines the
         standard input to the wall command as:

           HAPPY HOLIDAYS!
           Remember to turn in your time card.

FILES

     /usr/lib/cron               Main cron directory.
     /usr/spool/cron/crontabs    Spool area.
     /usr/lib/cron/cron.allow    List of allowed users.
     /usr/lib/cron/cron.deny     List of denied users.

RELATED INFORMATION

     The following commands:  "cron" and "sh."