crontab(1) crontab(1)
NAME
crontab - user crontab file
SYNOPSIS
crontab [file]
crontab -e [username]
crontab -r [username]
crontab -l [username]
DESCRIPTION
The crontab command copies the specified file, or standard
input if no file is specified, into a directory that holds all
users' crontab files.
The following options are available:
-e Edits a copy of the user's crontab file, or creates an
empty file to edit if one does not exist. If the editor
exits with a non-zero status, the existing crontab file is
left unchanged. When editing is complete, the file is
installed as the user's crontab file. The crontab command
determines which editor to invoke based on environmental
variables. When the POSIX2 environmental variable is set,
crontab invokes the editor specified by the EDITOR
environmental variable, and if that is null, it invokes
vi(1). When POSIX2 is not set, crontab invokes the editor
specified by the VISUAL environmental variable, and if
that is null, it invokes the editor specified by the
EDITOR environmental variable, and if that is null, it
invokes ed(1).
-l Lists the user's crontab file.
-r Removes the user's crontab from the crontab directory.
Only a privileged user can use username following the -e, -l,
or -r options, to edit, list, or remove the crontab file of
the specified user.
allow and deny files
Users can 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 determine if the user
should be denied access to crontab. If neither file exists,
only root can submit a job. If cron.allow does not exist and
cron.deny exists but is empty, global usage is permitted. The
Copyright 1994 Novell, Inc. Page 1
crontab(1) crontab(1)
allow and deny files consist of one user name per line.
crontab file
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
valid values) or a list of elements separated by commas. An
element is either a number or two numbers separated by a dash
(identifying 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 runs 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 runs 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 times specified. A percent
character in this field (unless escaped by \) is translated to
a newline 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.
Invocation environment
Any line beginning with a # is a comment and is ignored.
The shell is invoked from your HOME directory with an arg0 of
sh. Users who want 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).
Output
If you do not redirect the standard output and standard error
of your commands, any generated output or errors is mailed to
you.
Copyright 1994 Novell, Inc. Page 2
crontab(1) crontab(1)
FILES
/etc/cron.d/cron.allow list of allowed users
/etc/cron.d/cron.deny list of denied users
/usr/sbin/cron.d main cron directory
/var/spool/cron/crontabs spool area
/var/cron/log accounting information
/usr/lib/locale/locale/LC_MESSAGES/uxcore
language-specific message file
[See LANG on environ(5).]
NOTES
If you inadvertently enter the crontab command with no
arguments, exit using the Delete key. Do not exit with a
CTRL-d; if you do, then all entries in your crontab file will
be removed.
If a privileged user modifies another user's crontab file,
resulting behavior may be unpredictable. Instead, the
privileged user should first su(1M) to the other user's login
before making changes to the crontab file.
REFERENCES
at(1), cron(1M), sh(1), su(1M)
Copyright 1994 Novell, Inc. Page 3