Launch of Dating Tip Central Site
August 29th, 2006datingtipcentral.com provides up to date dating information and dating tips to help your dating success.
Launch of Shop Colon Cleanse Site
August 20th, 2006Launched a new site centered around the topic of Colon Cleanse.
HTML Character Codes
August 11th, 2006
|
HTTP/1.1 Response Codes
August 11th, 2006
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Unix Cron
August 11th, 2006Introduction
cron is a utility that you can use to schedule and automate tasks. By defining items in the cron table, called crontab, you can schedule any script or program to run on almost any sort of schedule.
For example, run a program each day 5 minutes after midnight on mondays, wednesdays and fridays. Or schedule something to run every five minutes, or once a month.
Basics
Each user has their own crontab, the scheduled scripts run as that user take this in account with regards to permissions. To edit the crontab use the following command:
$ crontab -e
You can list what your currnet crontab is using the
following command:
$ crontab -l
Crontab Format
The following is the format entries in a crontab must be. Note all lines starting with #are ignored, comments.
# MIN HOUR MDAY MON DOW COMMAND
5 * * * * echo ‘Hello’
| Item | Definition | Valid Values |
|---|---|---|
| MIN | Minute | 0-60 |
| HOUR | Hour [24-hour clock] | 0-23 |
| MDAY | Day of Month | 1-31 |
| MON | Month | 1-12 OR jan,feb,mar,apr … |
| DOW | Day of Week | 0-6 OR sun,mon,tue,wed,thu,fri,sat |
| COMMAND | Command to be run | Any valid command-line |
Examples
Here are a few examples, to see what some entries look like.
#Run command at 7:00am each weekday [mon-fri]
00 07 * * 1-5 mail_pager.script ‘Wake Up’
00 07 * * 1-5 mail_pager.script ‘Wake Up’
#Run command on 1st of each month, at 5:30pm
30 17 1 * * pay_rent.script
#Run command at 8:00am,10:00am and 2:00pm every day
00 8,10,14 * * * do_something.script
#Run command every 5 minutes during market hours
*/5 6-13 * * mon-fri get_stock_quote.script
#Run command every 3-hours while awake
0 7-23/3 * * * drink_water.script
Special Characters in Crontab
You can use an asterisk in any category to mean for every item, such as every day or every month.
You can use commas in any category to specify multiple values.
For example: mon,wed,fri
You can use dashes to specify ranges.
For example: mon-fri, or 9-17
You can use forward slash to specify a repeating range.
For example: */5 for every five minutes, hours, days
Special Entries
There are several special entries, some which are just shortcuts, that you can use instead of specifying the full cron entry.
The most useful of these is probably @reboot which allows you to run a command each time the computer gets reboot. This could be useful if you want to start up a server or daemon under a particular user, or if you do not have access to the rc.d/init.d files.
Example Usage:
# restart freevo servers
@reboot freevo webserver start
@reboot freevo recordserver start
@reboot freevo webserver start
@reboot freevo recordserver start
The complete list:
| Entry | Description | Equivalent To |
|---|---|---|
| @reboot | Run once, at startup. | None |
| @yearly | Run once a year | 0 0 1 1 * |
| @annually | (same as @yearly) | 0 0 1 1 * |
| @monthly | Run once a month | 0 0 1 * * |
| @weekly | Run once a week | 0 0 * * 0 |
| @daily | Run once a day | 0 0 * * * |
| @midnight | (same as @daily) | 0 0 * * * |
| @hourly | Run once an hour | 0 * * * * |
Miscelleanous Issues
Script Output
If there is any output from your script or command it will be sent to that user’s e-mail account, on that box. Using the default mailer which must be setup properly.
You can set the variable MAILTO in the crontab to specify a separate e-mail address to use. For example:
MAILTO=”admin@mydomain.com”
Missed Schedule Time
Cron does not run a command if it was missed. Your computer must be running for cron to run the job at the time it is scheduled. For example, if you have a 1:00am scheduled job and your computer was off at that time, it will not run the missed job in the morning when you turn it on.
Related Links
[brucemilton.com] At Command Mac OS X and eBay - at is similar to cron but for one time jobs, not reoccuring
CronniX Home page
CronniX is a Aqua (Mac OS X) front-end to the Unix utility cron. I haven’t used
this but looks pretty cool. If you prefer a GUI interface and have a Mac, check
it out. (Freeware)
Memorial to Tiger
August 4th, 2006Today we had to bid a fond farewell to our family cat named Tiger. He had developed a thyroid condition that was making him extremely thin, no matter how much he ate. This condition also caused him to loose partial control of his tongue so he could not lap up anything. The vet said that even if we got a Thyroidactomey he made never regain full use of it. He had even developed a bad case of arthritis in his hips and could not get around very well.
Tiger was almost 13 years old and was well natured cat that love to play and cuddle. Tonight the house feels very empty. He would always come into the office around 12:30am to remind me to feed him and to tell me it is time to call it a day.
He will be missed and this is my memorial to a good friend.