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CRONTAB(1) General Commands Manual CRONTAB(1)

crontab — maintain crontab files for individual users (V3)

crontab [-u user] file

crontab [-u user] { -l | -r [-f] | -e }

The crontab utility is the program used to install, deinstall or list the tables used to drive the cron(8) daemon in Vixie Cron. Each user can have their own crontab, and though these are files in /var, they are not intended to be edited directly.

If the allow file exists, then you must be listed therein in order to be allowed to use this command. If the allow file does not exist but the deny file does exist, then you must be listed in the deny file in order to use this command. If neither of these files exists, then depending on site-dependent configuration parameters, only the super user will be allowed to use this command, or all users will be able to use this command. The format of these files is one username per line, with no leading or trailing whitespace. Lines of other formats will be ignored, and so can be used for comments.

The first form of this command is used to install a new crontab from some named file or standard input if the pseudo-filename ‘-’ is given.

The following options are available:

Specify the name of the user whose crontab is to be tweaked. If this option is not given, crontab examines “your” crontab, i.e., the crontab of the person executing the command. Note that su(1) can confuse crontab and that if you are running inside of su(1) you should always use the -u option for safety's sake.
Display the current crontab on standard output.
Remove the current crontab. By default the -r option prompts for confirmation, adding the -f option will attempt to remove the current crontab without confirmation.
Edit the current crontab using the editor specified by the VISUAL or EDITOR environment variables. The specified editor edit the file in place; any editor that unlinks the file and recreates it cannot be used. After you exit from the editor, the modified crontab will be installed automatically.

/var/cron/allow
List of users allowed to use crontab
/var/cron/deny
List of users prohibited from using crontab
/var/cron/tabs
Directory for personal crontab files

A fairly informative usage message appears if you run it with a bad command line.

crontab(5), cron(8)

The crontab command conforms to IEEE Std 1003.2 (“POSIX.2”) with the exception that the dangerous variant of calling crontab without a file name in the first form of the command is not allowed by this implementation. The pseudo-filename ‘-’ must be specified to read from standard input. The new command syntax differs from previous versions of Vixie Cron, as well as from the classic SVR3 syntax.

Paul Vixie <paul@vix.com>

December 20, 2016 FreeBSD-12.0