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Full Discussion: Modify hour crontab UNIX
Top Forums UNIX for Dummies Questions & Answers Modify hour crontab UNIX Post 302877119 by varathaneie on Thursday 28th of November 2013 07:43:46 AM
Old 11-28-2013
I can give you an idea of how it can be done assuming that you want to change some details on this specific line in the cron file of all 60 servers,

You can run the below commands with ssh,
1. List all the server in a file
2. Read the file using for loop for one server at a time
3. For each server using ssh take cronfile backup like,

Code:
crontab -l > cronbackup_$i$date 
 
 ($i your server name,$date -date on whic you are doing it)

4. Next use sed command with -e option in ssh command and make your changes as below and write it to another file

Code:
sed 's#00 18 \* \* 1 /box/Pra/bin/systeme_reverse.ksh -s >/dev/null 2>&1# \
00 18 \* \* 3 /box/Pra/bin/new_script.ksh -s >/dev/null 2>\&1#g' cronbackup_$i$date > cronfile_new_$i$date

here we are chaning 2 things,
i, day of launch from 1 to 3
ii, script name from systeme_reverse.ksh to new_script.ksh

5. Now upload the new cronfile which has the edited content with ssh as below,

Code:
crontab cronfile_new_$i$date

Hope these steps could give you some idea!!!
 

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CRONTAB(1)						      General Commands Manual							CRONTAB(1)

NAME
crontab - maintain crontab files for individual users (ISC Cron V4.1) SYNOPSIS
crontab [-u user] file crontab [-u user] [-l | -r | -e] DESCRIPTION
Crontab is the program used to install, deinstall or list the tables used to drive the cron(8) daemon in ISC Cron. Each user can have their own crontab, and though these are files in /var, they are not intended to be edited directly. If the cron.allow file exists, then you must be listed therein in order to be allowed to use this command. If the cron.allow file does not exist but the cron.deny file does exist, then you must not be listed in the cron.deny file in order to use this command. If neither of these files exists, only the super user will be allowed to use this command. If the -u option is given, it specifies the name of the user whose crontab is to be tweaked. If this option is not given, crontab examines "your" crontab, i.e., the crontab of the person executing the command. Note that su(8) can confuse crontab and that if you are running inside of su(8) you should always use the -u option for safety's sake. The first form of this command is used to install a new crontab from some named file or standard input if the pseudo-filename ``-'' is given. The -l option causes the current crontab to be displayed on standard output. The -r option causes the current crontab to be removed. The -e option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR environment variables. After you exit from the editor, the modified crontab will be installed automatically. SEE ALSO
crontab(5), cron(8) FILES
/etc/cron.allow /etc/cron.deny STANDARDS
The crontab command conforms to IEEE Std1003.2-1992 (``POSIX''). This new command syntax differs from previous versions of Vixie Cron, as well as from the classic SVR3 syntax. DIAGNOSTICS
A fairly informative usage message appears if you run it with a bad command line. AUTHOR
Paul Vixie <vixie@isc.org> 4th Berkeley Distribution 29 December 1993 CRONTAB(1)
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