Cron is a job scheduler that allows users to run commands periodically.

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Check if script is started by cron, rather than invoked manually

Is there any variable that cron set when it's running a program ? If the script is running by cron, I'll skip some parts; otherwise invoke those parts. How can I know if the bash script is started by ...
7
votes
2answers
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Can I automate tar's multi-volume-feature?

Ok, so I've just had a read through this page after a way to improve my current backup solution on my Debian server. Tar seems to be offering a quite nice multi-volume feature, although when I try it ...
7
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4answers
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Cron running job every 15 seconds

Could you advise me what to write in crontab so that it runs some job (for testing I will use /usr/bin/chromium-browser) every 15 seconds?
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/etc/cron.daily/foo : Send email to a particular user instead of root?

I'm running CentOS 5.5. We have several cronjobs stored in /etc/cron.daily/ . We would like the email for some of these cronjobs to go to a particular email address, while the rest of the emails in ...
7
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1answer
3k views

List of modified files of the past 24 hours

Is there a reliable way to have a system that mails me the list of files that were modified in the past 24 hours inside a set of directories? (like /home/*/public_html/* and /home/*/*domains/*)
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Have cron email output to MAILTO based on exit status

I have a cron job running a php command like this: php /path/to/script.php > dev/null This should send only STDERR output to the MAILTO address. From what I gather the php script is not ...
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10k views

Can I change the default mail recipient on cron jobs?

I believe that if there is any output from a cronjob it is mailed to the user who the job belongs to. I think you can also add something like MAILTO=vivek@nixcraft.in at the top of the cron file to ...
7
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1answer
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How to autostart a background program by a non-root user?

As a non-root user, I want to run a background job when the system boots. It's sort of a service which doesn't require root privilege. Is there a way to do it? One way is to put sudo -u user command ...
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Meaning of “* */1 * * *” cron entry?

Somehow, I am finding it difficult to understand tweaking around * parameters with cron. I wanted a job to run every hour and I used the below setting: * */1 * * * But it does not seem to do the ...
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What's wrong with these two cron job's?

I have the following cron jobs defined. 55 8 * * 3 /usr/bin/php /home/mark/dev/processes/customClient/events.php > /home/mark/dev/processes/customClient/events-`date +%Y-%m-%d ...
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sort at jobs chronologically

Possibly a simple solution I misplaced. How can I get the output of atq sorted chronologically, so I can easily see who's due to run next? The man page for sort doesn't have anything built-in to ...
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System Crontab or Root Crontab

System crontab: /etc/crontab Root crontab: sudo crontab -u root -e Which way is preferred? As they all run tasks within administration privilege.
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Logging ALL stderr output of crontab to file

For example, I can log stderr of one script in this way: * * * * * run_script.sh > /var/log.txt 2>&1 But I want to log stderr of all scripts in my crontab. I can append > /var/log.txt ...
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3answers
3k views

What could cause a cron to run twice at the same moment?

I have a cron that is setup to run every Monday at 1 AM 0 1 * * 1 /script/dir/script >> /script/dir/file.log After two years of running as expected, it ran twice on June 18, with the second ...
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1answer
72 views

How can I make `sudo crontab -e` use my `sudoedit` environment?

I've started using sudoedit <file> instead of sudo vim <file>. One of the advantages is that it uses my local ~/.vimrc. However, when using sudo crontab -e, it uses /root/.vimrc instead. ...
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votes
2answers
2k views

Open emacs in a terminal when editing crontab

I have setup emacs as my default editor in /etc/profile. When I want to use emacs in a terminal. I open it with the -nw option. How can I have the same behavior when doing a crontab -e preventing it ...
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3answers
2k views

Cron to not run on specific day but all other days

I have a cron setup to execute a bash script daily at 10pm. I have another cron setup to run monthly on the 1st of the month. Both crons launch a bash script, and the only different in the bash script ...
5
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2answers
372 views

cron every X exact meaning

In cron you can specify */n where n means every n times period, for instance in the first column is minute. */5 means every 5 minutes, but which minutes? 0, 5, 10, ...? What happens if the number ...
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3answers
9k views

How to add unique id to file name in cron job?

My cronjob looks like this: 5 3 * * * mysqldump -u root test > /srv/backup/mysql_daily.dump How can I make filename unique for every time when cronjob writes mysql_daily.dump?
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3answers
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How can I ensure my cronjob will run at specified time?

I'd like to know how I can check to see if my cronjob will run at the specified time I set it at. Is there anyway I can test this without having to wait for that time? Here are my crontab -l results: ...
5
votes
2answers
27k views

Cron job to delete files older than 3 days

I need to remove files older than 3 days with a cron job in 3 different directories. (these 3 directories are children of a parent directory /a/b/c/1 & /a/b/c/2 & /a/b/c/3) Can this be done ...
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2answers
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why doesn't 0 0 * * 1 root hostname >> /tmp/hostname.txt work as a crontab?

0 0 * * 1 root hostname >> /tmp/hostname.txt The above cron entry should run midnight on monday and create a file in /tmp called hostname.txt with the output of the hostname command. But it is ...
5
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4answers
352 views

Change the time zone of a cronjob

I have a cronjob which is executes every day at 9:00 AM of UTC-Time. I'm in GMT+1 so it executes at 10:00 AM local time. When there is the timezone change (to daylight saving time, DST), the cronjob ...
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3answers
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How to start a cron job without reboot?

I use a cron job to call offlineimap every 2 minutes: */2 * * * * /usr/bin/offlineimap > ~/Maildir/offlineimap.log 2>&1 I needed to kill the cron job to fix a problem. How can I then ...
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3answers
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How to get which version of cron daemon is running

Background: I am working on CentOS Details # cat /proc/version Linux version 2.6.18-308.4.1.el5PAE (mockbuild@builder10.centos.org) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-52)) #1 SMP Tue Apr 17 ...
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921 views

Crontab job not emailing on failure

I have a cron job on Debian: 1 * * * * /home/paradroid/bin/myscript.sh >/dev/null There is an installed and configured MTA, and I have received emails when the script has a syntax error, so I ...
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2answers
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How can I know when a cron job was killed or it crashed?

Usually when a cron job crash, it will leave some error messages in the log. We run shell script and some java program with cron job. Recently we found some weird thing out from the log. Obviously ...
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2answers
443 views

Does cron know that the instance to be scheduled is already running?

I was wondering if we add a job in the crontab e.g. to run every 5 mins and the job does not actually manage to finish in 5 mins, does the cron daemon know that the previous instance is already ...
5
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3answers
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Cron allowed special character “L” for “Last day of the month” on Debian

I'd like to know if L is one of the allowed special characters on Debian's cron implementation? I'm trying to set up a cron to run on the last day of every month. From the cron entry on wikipedia: ...
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Frustrating issue where neither cron nor su -c runs my job (permissions?)

Updated (and snipped) with more details below. I've set up a cron script and I'm trying to debug why it's not running. [Snipped context testing, which is all ok; see revision 2 for details] The ...
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Is any extended logging available for cron jobs?

I have 3 scripts under /etc/cron.daily. My cron logs are written in /var/log/cron. The below is an entry for the above cron that has run. (root) CMD (run-parts /etc/cron.hourly) Here the stdout or ...
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3answers
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Crontab entry with hour range going over midnight

Is this valid crontab time specification, doing what is expected: 0 22-4 * * * Or is it necessary to do something like 0 22,23,0,1,2,3,4 * * *
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3answers
856 views

Cronjob to run script every 3 weeks on Wednesday

Is it possible to schedule a cron job that would run every three weeks on Wednesday (8AM) only? Or, if that is not possible, to run a job every 27 days or less but on Wednesday at 8AM.
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3answers
830 views

Where to put system cronjobs?

If I need a cronjob that runs at system level (i.e. not specific for a certain user) how do you suggest me to create it? running crontab -e as root appending it to /etc/crontab creating a file ...
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How can I use cron to display messages on the screen via notify-send

I am toying around with notify-send and cron (on an Arch machine) and I can't figure out a way to combine them: I tried the solution given here and here, but neither worked. How can I use them? ...
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3answers
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Running a script during booting/startup; init.d vs cron @reboot

I am currently trying to understand the difference between init.d and cron @reboot for running a script at startup/booting of the system. The use of @reboot (this method was mentioned in this forum ...
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1answer
450 views

BASH_ENV and cron jobs

I have several questions related to non-interactive, non-login shells and cron jobs. Q1. I have read that non-interactive, non-login shells only "load" $BASH_ENV. What does this exactly mean? Does ...
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2answers
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Scp doesn't work in cron

Yeah, I know it's classic. I've googled it all around, but still it doesn't work. I have the following script: #First go to SVN repo folder cd $svnrepos # Just make sure we have write access to ...
5
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1answer
2k views

Cron job still running when deleted

On a server I inherited, there is a cron job running hourly on one of the Debian servers. It sends an email out to a non-existent email, but bounces back to my account since I listed myself as the ...
5
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2answers
303 views

How to schedule a job that depends on network availability?

I have cloned a git repository of some project. I want to automate git pull and compile the project once in a week. I am using a laptop which wont be on 24x7. Now, I cannot use cron as I should keep ...
5
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1answer
92 views

When I schedule a command with 'at', can I change where the output is mailed to?

When I schedule a job/command with at to be executed in the future, the standard output and error of the command is "mailed" to the user that did the scheduling. So after my job runs, I get a message ...
5
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1answer
615 views

Run script when specific users logout

I need to run my application in screen when specific users are logged out and kill the screen when someone from my user list logged in. So I am thinking about bash script, which will be called ...
5
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2answers
357 views

How can I peek at the output of a running crontab task on OpenBSD?

I have an hourly hour-long crontab task running with some mtr (traceroute) output every 10 minutes (that is going to go for over an hour prior to it being emailed back to me), and I want to see the ...
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1answer
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Running cron script with lynx fails to work

I'm trying to automate a login process that can only be done through a browser. I am using the lynx browser to script the actions required to do this. Lynx does this by dumping a user's keystrokes ...
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CRON Permission Denied [closed]

I have a Debian 7. 3 Server with WebMin installed. I configured a cron job to run every minute as root user, so I run the command crontab -l when I'm logged in as root it shows: * * * * * ...
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840 views

Location of the crontab file

as many (most?) others, I edit my crontab via crontab -e, where I keep all routine operations such as incremental backup, ntpdate, various rsync operations, as well as making my desktop background ...
4
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2answers
261 views

Upgrading packages automatically

I'm fairly new to using servers (debian 7) and I'm currently running cron-apt to e-mail me when there are new upgrades available. Is the following command safe to run when new upgrades are shown? ...
4
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2answers
839 views

Schedule job at irregular intervals

It's simple enough to use cron to schedule a job to occur periodically. I'd like to have something occur less regularly -- say, run the job, then wait 2 to 12 hours before trying again. (Any ...
4
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2answers
8k views

Cronjob to run every 30 minutes

I want to set a cronjob entry that runs a script every 30 minutes from 9:00 to 18:00 but I do not want it to run at 18:30. The script should run for the first time at 9:00 and for the last time at ...
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Is setting a higher nice level for a process an effective way to reduce its impact on system load/CPU time?

I have an rsync cron job which is pushing the server load and triggering monitor alerts. If I set the job to be run with a high nice level, would that effectively reduce the impact it has on system ...