CRONTAB(1) (User Environment Utilities) CRONTAB(1)
NAME
crontab - user crontab file
SYNOPSIS
crontab [file]
crontab -r
crontab -l
DESCRIPTION
crontab copies the specified file, or standard input if no
file is specified, into a directory that holds all users'
crontabs. The -r option removes a user's crontab from the
crontab directory. crontab -l will list the crontab file
for the invoking user.
Users are permitted to use crontab if their names appear in
the file /usr/lib/cron/cron.allow. If that file does not
exist, the file /usr/lib/cron/cron.deny is checked to
determine if the user should be denied access to crontab. If
neither file exists, only root is allowed to submit a job.
If cron.allow does not exist and cron.deny exists but is
empty, global usage is permitted. The allow/deny files
consist of one user name per line.
A crontab file consists of lines of six fields each. The
fields are separated by spaces or tabs. The first five are
integer patterns that specify the following:
minute (0-59),
hour (0-23),
day of the month (1-31),
month of the year (1-12),
day of the week (0-6 with 0=Sunday).
Each of these patterns may be either an asterisk (meaning
all legal values) or a list of elements separated by commas.
An element is either a number or two numbers separated by a
minus sign (meaning an inclusive range). Note that the
specification of days may be made by two fields (day of the
month and day of the week). If both are specified as a list
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CRONTAB(1) (User Environment Utilities) CRONTAB(1)
of elements, both are adhered to. For example, 0 0 1,15 * 1
would run a command on the first and fifteenth of each
month, as well as on every Monday. To specify days by only
one field, the other field should be set to * (for example,
0 0 * * 1 would run a command only on Mondays).
The sixth field of a line in a crontab file is a string that
is executed by the shell at the specified times. A percent
character in this field (unless escaped by \) is translated
to a new-line character. Only the first line (up to a % or
end of line) of the command field is executed by the shell.
The other lines are made available to the command as
standard input.
The shell is invoked from your $HOME directory with an arg0
of sh. Users who desire to have their .profile executed
must explicitly do so in the crontab file. Cron supplies a
default environment for every shell, defining HOME, LOGNAME,
SHELL(=/bin/sh), and PATH(=:/bin:/usr/bin:/usr/lbin).
If you do not redirect the standard output and standard
error of your commands, any generated output or errors will
be mailed to you.
FILES
/usr/lib/cron main cron directory
/usr/spool/cron/crontabsspool area
/usr/lib/cron/log accounting information
/usr/lib/cron/cron.allowlist of allowed users
/usr/lib/cron/cron.denylist of denied users
SEE ALSO
sh(1).
cron(1M) in the System Administrator's Reference Manual.
WARNINGS
If you inadvertently enter the crontab command with no
argument(s), do not attempt to get out with a ctrl-d. This
will cause all entries in your crontab file to be removed.
Instead, exit with a DEL.
Page 2 May 1989