CRONTAB(1) RISC/os Reference Manual CRONTAB(1)
NAME
crontab - user crontab file
SYNOPSIS
crontab [file]
crontab -e [ username ]
crontab -l [ username ]
crontab -r [ username ]
DESCRIPTION
crontab copies the specified file, or standard input if no
file is specified, into a directory that holds all users'
crontabs. The e option edits a copy of the current user's
crontab file, or creates an empty file to edit if crontab
does not exist. When editing is complete, the file is
installed as the user's crontab file. If a username is
given, the specified user's crontab file is edited, rather
than the current user's crontab file; this may only be done
by a privileged user. The environment variable EDITOR
determines which editor is invoked with the e option. The
default editor is vi(1). crontab -l will list the crontab
file for the invoking user. The r option removes a user's
crontab from the crontab directory. Only a privileged user
can specify a username following the r or l options to
remove or list the crontab file of the specified user.
Users are permitted to use crontab if their names appear in
the file /etc/cron.d/cron.allow. If that file does not
exist, the file /etc/cron.d/cron.deny is checked to deter-
mine 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 con-
sist 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
of elements, both are adhered to. For example, 0 0 1,15 * 1
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CRONTAB(1) RISC/os Reference Manual CRONTAB(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 stan-
dard input.
Any line beginning with a # is a comment and will be
ignored.
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
/etc/cron.d main cron directory
/var/spool/cron/crontabs spool area
/var/cron/log accounting information
/etc/cron.d/cron.allow list of allowed users
/etc/cron.d/cron.deny list of denied users
SEE ALSO
atq(1), atrm(1), sh(1), su(1), vi(1).
cron(1M) in the System Administrator's Reference Manual.
NOTES
If you inadvertently enter the crontab command with no
argument(s), do not attempt to get out with a CONTROL-D.
This will cause all entries in your crontab file to be
removed. Instead, exit with a DEL.
If a privileged user modifies another user's crontab file,
resulting behavior may be unpredictable. Instead, the
privileged user should first su(1) to the other user's login
before making any changes to the crontab file.
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