I want to know how to Sechudle job using at and crontab so
please give the explain with example please do the needful
Regards
Visva
Answers were Sorted based on User's Feedback
Answer / kiranraj
1. Crontab Restrictions
____________
You can execute crontab if your name appears in the
file /usr/lib/cron/cron.allow. If that file does not exist,
you can use
crontab if your name does not appear in the
file /usr/lib/cron/cron.deny.
If only cron.deny exists and is empty, all users can use
crontab. If neither file exists, only the root user can use
crontab. The allow/deny files consist of one user name per
line.
2. Crontab Commands
__________
export EDITOR=vi ;to specify a editor to open crontab file.
crontab -e Edit your crontab file, or create one if it
doesn't already exist.
crontab -l Display your crontab file.
crontab -r Remove your crontab file.
crontab -v Display the last time you edited your
crontab file. (This option is only available on a few
systems.)
3. Crontab file
___________
Crontab syntax :-
A crontab file has five fields for specifying day , date
and time followed by the command to be run at that
interval.
* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6)
(Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)
* in the value field above means all legal values as in
braces for that column.
The value column can have a * or a list of elements
separated by commas. An element is either a number in the
ranges shown above or two numbers in the range separated by
a hyphen (meaning an inclusive range).
Note: The specification of days can be made in two fields:
month day and weekday. If both are specified in an entry,
they are cumulative meaning both of the entries will get
executed .
4. Crontab Example
_______
A line in crontab file like below removes the tmp files
from /home/someuser/tmp each day at 6:30 PM.
30 18 * * * rm /home/someuser/tmp/*
Is This Answer Correct ? | 11 Yes | 0 No |
Answer / ashok
crontab -e
minuts 0-69
hours 0-24
days 0-30
month 0-12
years
Is This Answer Correct ? | 2 Yes | 11 No |
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