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Full Discussion: differnce between working of at and crontab commands
Top Forums UNIX for Dummies Questions & Answers differnce between working of at and crontab commands Post 70768 by Just Ice on Tuesday 3rd of May 2005 11:43:52 PM
Old 05-04-2005
at is usually for non-regular, one-time-only jobs while cron is usually for regular, perpetual jobs ...

at samples:
Code:
# harass the console user at 7:05 pm
at 1905
echo "This is my console!" > /dev/console
# reboot the box 1 hour from now
at now + 1 hour
sync; sync; reboot

cron samples:
Code:
# reboot host every weekday @ 8:30 pm
30 20 * * 0-5 (sync; sync; init 6) > /dev/null 2>&1
# annoy the console user every weekday @ 8:00 am
00 08 * * 0-5 echo "This is my concole!" > /dev/console

however, you can also get a job to go regularly with an at command by adding something like this in your script ...
Code:
at now + 1 week << GO
/path/to/this/script > /dev/null 2>&1
GO

... and a "one-time" job in cron ... (will only run when all time conditions are met) ...
Code:
# run the job at 1:01 am Monday, January 1
01 01 01 01 1 echo "This is my console!" > /dev/console

btw, it would be best if you get into checking the man pages while you're just starting ... see "man at" and "man crontab" ...
 

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LEARN ABOUT DEBIAN

kep_reload

KEP_RELOAD(1)						      General Commands Manual						     KEP_RELOAD(1)

NAME

       kep_reload - Update Predict's Keplerian elements

SYNOPSIS

	kep_reload

DESCRIPTION

       KEP_RELOAD is a simple utility that forces an immediate reload of PREDICT's Keplerian database through a socket connection while PREDICT is
       running in server mode.	It is especially useful in environments where PREDICT runs continuously, and periodic  Keplerian  element  updates
       are made outside of PREDICT, such as through scripts run through a crontab.

       The  "kepupdate"  script  found	in this directory is an example of a Keplerian element update script that can be run on an automated basis
       through a crontab.  It is designed to be placed in your home directory under a subdirectory  called  "cronjobs".   It  downloads  Keplerian
       orbital	data  from  www.celestrak.com  using  the  HTTP  protocol.   (The  "wget" utility, available from the Free Software Foundation, is
       required, and is included in many Linux distrubutions.)

       Type crontab -e to edit your crontab.  Simply add the following entry:

	       0 8 * * * kepupdate

       and your orbital database will update each morning at 8:00 AM (provided you have a network connection at that time).

       See the crontab man page for more information on editing your crontab.

AUTHOR

       This man page was written by A. Maitland Bottoms, AA4HS, for Debian GNU/Linux.

								  31 August 2003						     KEP_RELOAD(1)
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