Unix Cron format

Cron format - crontab

crontab -l


1. minute (from 0 to 59)
2. hour (from 0 to 23)
3. day of month (from 1 to 31)
4. month (from 1 to 12)
5. day of week (from 0 to 6) (0=Sunday)


1  2  3  4  5  6
*  *  *  *  *  *
|  |  |  |  |  | 
|  |  |  |  |  +-- Year              (range: 1900-3000)
|  |  |  |  |
|  |  |  |  +---- Day of the Week    (range: 1-7, 1 standing for Monday)
|  |  |  |
|  |  |  +------ Month of the Year   (range: 1-12)
|  |  |
|  |  +-------- Day of the Month     (range: 1-31)
|  |
|  +---------- Hour                  (range: 0-23)
|
+------------ Minute                 (range: 0-59)



* * * * * /xxx/xxx/xx/anuj.sh


if 5 stars then



1. every minute
2. of every hour
3. of every day of the month
4. of every month
5. and every day in the week.



Execute every Friday 1AM

So if we want to schedule script to run at 1AM every Friday,


0 1 * * 5 /xxx/xxx/xx/anuj.sh

The script is now being executed when the system clock hits:

1. minute: 0
2. of hour: 1
3. of day of month: * (every day of month)
4. of month: * (every month)
5. and weekday: 5 (=Friday)
=================================================================

##┌───────────── minute (0 - 59)
# │ ┌───────────── hour (0 - 23)
# │ │ ┌───────────── day of month (1 - 31)
# │ │ │ ┌───────────── month (1 - 12)
##┌───────────── minute (0 - 59)
# │ ┌───────────── hour (0 - 23)
# │ │ ┌───────────── day of month (1 - 31)
# │ │ │ ┌───────────── month (1 - 12)
# │ │ │ │ ┌───────────── day of week (0 - 6) (Sunday to Saturday;
# │ │ │ │ │                                       7 is also Sunday)
# │ │ │ │ │
# │ │ │ │ │
# * * * * *  command to execute

======================================================================

Execute on Mon to friday


So if we want to schedule the script to Monday till Friday at 1 AM


0 1 * * 1-5 /bin/execute/this/script.sh

The script is now being executed when the system clock hits:

1. minute: 0
2. of hour: 1
3. of day of month: * (every day of month)
4. of month: * (every month)
5. and weekday: 1-5 (=Monday til Friday)



# Minute   Hour   Day of Month       Month          Day of Week        Command    
# (0-59)  (0-23)     (1-31)    (1-12 or Jan-Dec)  (0-6 or Sun-Sat)                
    0        2          12             *                *            /usr/bin/find




Examples:

*/30 * * * * /aptus/oracle/admin/aptdb/script/check_oracle_tablespace.sh -c aptdb -w 90 -c95 > /tmp/tablespace.nagios

5 5 * * * /aptus/oracle/admin/aptdb/script/scheduler.sh > /dev/null 2>&1

# 5 6 * * * /aptus/oracle/admin/aptdb/script/exp_solomon.sh > /dev/null 2>&1



Standard output (STDOUT) and standard errors (STDERR).

STDOUT is marked 1, STDERR is marked 2.

So the following statement tells Linux to store STDERR in STDOUT as well, creating one datastream for messages & errors:

2>&1


every hr ....


***-amd-02:/home/anujs/Downloads # crontab -l
# DO NOT EDIT THIS FILE - edit the master and reinstall.
# (/tmp/crontab.XXXXwcdEfa installed on Tue Sep 7 10:10:07 2010)
# (Cron version V5.0 -- $Id: crontab.c,v 1.12 2004/01/23 18:56:42 vixie Exp $)

59 * * * * echo " ">/var/log/warn > /dev/null 2>&1

59 * * * * echo " ">/var/log/messages > /dev/null 2>&1



cron and email confirmation .....

15 22 * * * /xxxx/oracle/admin/xxdb/scripts/Rmanbackup.sh 2>&1 | mail -s "RMAN BACKUP On (xxx-xxx-01) completed... " anuj.singh@xxxx.co.uk