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Your Virtual Private Servers crontab can be stored in any file you
choose. For example, you may wish to create or upload a file called
cronjobs in your Virtual Private Servers home directory for
your cron table. Each line in your crontab will either be an environment
variable setting, a cron table entry, or a comment (beginning with
the "#" character).
An environment variable setting in
a crontab looks like this:
NAME = VALUE
Several environment variables are set
up automatically by the cron daemon, depending on your Virtual Private
Servers O/S.
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FreeBSD
The cron environment variables include SHELL, LOGNAME, USER,
and HOME. In addition to these, there is a special MAILTO environment
variable. Any output generated by your cron jobs will be sent
to the address specified by MAILTO (if it is not specified it
will be sent to the owner of the crontab). If MAILTO is defined
as an empty string then no mail will be sent.
MAILTO = ""
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Solaris
The cron environment variables include SHELL, LOGNAME, USER,
and HOME. In order to use command and file paths that include
the "~" character, set the SHELL variable this way:
SHELL = "/bin/bash"
The format of a cron table entry includes
five (5) time fields followed by a command. Commands are executed
when the time specified by the date fields matches the current time.
The five time fields are as follows:
Field Allowed Values
----- --------------
Minute 0-59
Hour 0-23
Day of Month 1-31
Month 1-12, jan, feb, mar, apr, may, jun, jul, aug, sep, oct,
nov, dec
Day of Week 0-7, sun, mon, tue, wed, thu, fri, sat (0 and 7 are "sun")
A field may be an asterisk (*), which
indicates all values in the range are acceptable. Ranges of numbers
are allowed, i.e. "2-5" or "8-11", and lists
of numbers are allowed, i.e. "1,3,5" or "1,3,8-11".
Step values can be represented as a sequence, i.e. "0-59/15",
"1-31/3", or "*/2".
The actual command you wish to execute,
including any parameters to be passed to it, is the sixth, and final
field of a cron table entry.
NOTE:
Each cron table entry must have a trailing line break in order
for the cron table entry to be recognized. |
Some examples of complete cron table
entries are show below, implementing the vnukelog
command as an example.
# Any output generated by the cron entries below is sent to the e-mail
# address assigned to the MAILTO environment variable.
MAILTO="webmaster@mycompany.com"
# Execute the "vnukelog" command at 1:15 (15 1) AM every day.
15 1 * * * /usr/local/bin/vnukelog
# Execute the "vnukelog" command at 11:40 PM (40 23) on the first day (1)
# of each month.
40 23 1 * * /usr/local/bin/vnukelog
# Execute the "vnukelog" command every 10 minutes for for the first
# half-hour (0-30/10) of the 9:00 AM and 5:00 PM hours (9,17) on
# Monday-Friday (1-5).
0-30/10 9,17 * * 1-5 /usr/local/bin/vnukelog
# Execute the "vnukelog" command at 4:00 AM, 8:00 AM, 12:00 noon, 4:00 PM,
# and 8:00 PM (0 */4) on each Sunday (sun) every January (jan).
0 */4 * jan sun /usr/local/bin/vnukelog
# Execute the "vnukelog" command at 4:30 AM (30 4) on the first, fifteenth
# (1,15), and each Friday (fri) of every month.
30 4 1,15 * fri /usr/local/bin/vnukelog
# Execute the "vnukelog" command at 12:00 midnight (0 0) on August 19 (8)
# (aug).
0 0 19 8 * /usr/local/bin/vnukelog
0 0 19 aug * /usr/local/bin/vnukelog
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