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Can be mailed to the crontab owner, can be mailed to a person other than the crontab owner or the feature can be turned off and no mail will be sent at all
This can be done by telling cron which display to use.
00 06 * * * env DISPLAY=:0 gui_appnameThe env DISPLAY=:0 portion will tell cron to use the current display (desktop) for the program "gui_appname".
And if you have multiple monitors, don't forget to specify on which one the program is to be run. For example, to run it on the first screen (default screen) use :
00 06 * * * env DISPLAY=:0.0 gui_appnameThe env DISPLAY=:0.0 portion will tell cron to use the first screen of the current display for the program "gui_appname".
... A trivial example is:* * * * * cat - % another minute has passedThis would output the textanother minute has passedAfter the first %, all other %s in a crontab entry indicate a new line. So a slightly different trivial example is:* * * * * cat - % another % minute % has % passedThis would output the textanother minute has passedNote how the % has been used to indicate a new line.The problem is how to use a % in a crontab line to as a % and not as a new line. Many manuals will say escape it with a \. This certainly stops its interpretation as a new line but the shell running the cron job can leave the \ in. For example:
* * * * * echo '\% another \% minute \% has \% passed'would output the text\% another \% minute \% has \% passedClearly, not what was intended.A solution is to pass the text through sed. The crontab example now becomes:
* * * * * echo '\% another \% minute \% has \% passed'| sed -e 's|\\||g'This would output the text% another % minute % has % passedwhich is what was intended.This technique is very useful when using a MySQL command within a crontab. MySQL command can often have a % in them. Some example are:
SET @monyy=DATE_FORMAT(NOW(),"%M %Y") SELECT * FROM table WHERE name LIKE 'fred%'So, to have a crontab entry to run the MySQL commandmysql -vv -e "SELECT * FROM table WHERE name LIKE Fred%'" member_listwould have to appear in the crontab asecho "SELECT * FROM table WHERE name LIKE 'Fred\%'" | sed -e 's|\\||g' | mysql -vv member_listPulling the crontab entry apart there is:the echo command sends the MySQL command to STDOUT where it is piped into sed which removes any back slashes before sending the output to STDOUT where it is piped into the mysql command processor which reads its commands from STDIN
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This is all documented very nicely in the cron manpage: $man cron Cron should be started from /etc/rc.d/init.d or /etc/init.d Cron searches /var/spool/cron for crontab files which are named after accounts in crontabs found are loaded into memory. Cron also searches for /etc/crontab and the files in the directory, which are in a different format (see crontab(5) ). Cron then wakes up every minute, examining all stored crontabs, checking each command to see if it should be run in the current minute. When executing commands, any output is mailed to the owner of the crontab (or to the user named in the MAILTO environment variable in the crontab, if such exists). If we look at /etc/crontab we see how each of the cron.{hourly,daily,weekly,monthly} crontabs are executed: $cat /etc/crontab SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root HOME=/ # run-parts 01 * * * * root run-parts /etc/cron.hourly 02 4 * * * root run-parts /etc/cron.daily 22 4 * * 0 root run-parts /etc/cron.weekly 42 4 1 * * root run-parts /etc/cron.monthly And if we look at the file in /etc/cron.daily we see a crontab for logrotate. Because cron.daily is run every morning at 4:02am we can expect logrotate to run around that time. The logrotate script say to move the squid log files out of the way /var/log/squid/access.log { weekly rotate 5 copytruncate compress notifempty missingok } ... <snipped other logfile entries> /var/log/squid/store.log { weekly rotate 5 copytruncate compress notifempty missingok # This script asks squid to rotate its logs on its own. # Restarting squid is a long process and it is not worth # doing it just to rotate logs postrotate /usr/sbin/squid -k rotate endscript } The final logrotate statement above tells squid to rotate the log files: /usr/sbin/squid -k rotate For other ways of rotating the logs the Squid FAQ is indespensible: http://wiki.squid-cache.org/SquidFaq/SquidLogs#head-df8a4e31ffc62c98268eb3e7774f7c4f0735fac9 and/or here: http://docstore.mik.ua/squid/FAQ-6.html HTH. Cheers, Harry On Mon, 2009-03-02 at 10:24 +0200, a bv wrote: > Hi all, > > I would like to daily logrotate the squid log files at everyday at > 00:00(midnight) at some RHEL 5.x systems. I havent used cron things > for a long time so i forgot all about it. Also i have the > logrotate.conf and /etc/logrotate.d/squid file. > > i have tried to add a /usr../sbin/rotate -k thing as a cron job but it > seem to be unsuccessfull. Googling makes some mind mixing samples > etc. also using crontab -e command brings an empty file, other than > the one i find crontab. > > So is there someone who will shortly explain the cron related files > and usage , also making the squid rotate its daily logs easily. Most > of the resources (including books) makes confusing the minds at these > simple subjects. Couldnt see a step by step guide. > > Regards >
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