THE VIRTUAL SERVER HANDBOOK

An asterisk (*) may be used as a wildcard meaning "first through last". The

asterisk is used when you want an event to occur for every allowable value.

For example, if you wanted to schedule your log files to be purged on a

monthly basis you could place an asterisk in the Day of Month field. As you

might imagine, it would be unwise to put an asterisk in the Minute field of

the Cronfile as it may cause too much of a load on your Virtual Server.

Ranges such as two numbers separated with a hyphen ( ) are allowed. For

example, if you wanted the Cron to send you E mail to warn you that your

taxes are due April 15th, and you want to be warned starting in January

until they are due in April, you could create a Cronfile with the value 1 4 in

the month field, and the Cron would run starting in January until April. You

can specify a list of values by separating the numbers with a comma. For

example, 1,7,9,10 would be the months January, July, September, and

October. Skip values can be specified with the "/" sign. For example, 1 12/2

would be "every other month". Names can also be used for the month and

day of the week fields. The first three letters of the month or day can be

used. This option is not allowable with ranges or lists.

Here are some additional examples of valid time/date values:

Example:

What it does (examples are in the hour field)

8 12

Event will execute each hour in the range 8,9,10,11,12

1,4,5,7

Event will execute each hour specified 1,4,5,7

0 4,8 12

Event will execute each in the two ranges

0 23/2

Event will execute every other hour 2,4,6,8....

*/2

Same as above

The sixth field in a Cron file (i.e., rest of the Cron line) are where you place

the command you want to run. The entire command portion, up to the

newline character or the % character will be executed by /bin/sh (or the

shell you have specified with the SHELL environmental variable). Percent

signs in the command, unless they are escaped with a backslash (\) will be

changed into newline characters and all data after the first % will be sent to

the command as standard input.

Example Cron for mailing a notice about taxes:

# This is a comment.

SHELL=/bin/csh

MAILTO=johndoe@somedomain.com

5 22 14 1 4 * mail  s "Your taxes are due on

April 15th"

judy@somedomain.com%Judy,%%Fill out your taxes!%

Note:  Do not place hard returns in Cron commands (the line wraps on

its own). Hard returns tell Cron that the end of the Cron command has

occurred.

Example Cron for deleting logs monthly:

MAILTO=johndoe@somedomain.com

1 3 * * * /usr/local/bin/virtual vnl  r

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