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

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36
votes
3answers
15k views

How can I execute `date` inside of a cron tab job?

I want to create a log file for a cron script that has the current hour in the log file name. This is the command I tried to use: 0 * * * * echo hello >> ~/cron-logs/hourly/test`date "+%d"`.log ...
43
votes
11answers
30k views

Correct locking in shell scripts?

Sometimes you have to make sure that only one instance of a shell script is running at the same time. For example a cron job which is executed via crond that does not provide locking on its own (e.g. ...
14
votes
6answers
6k views

Using notify-send with cron

I am using Arch Linux with KDE/Awesome WM. I am trying to get notify-send to work with cron. I have tried setting DISPLAY/XAUTHORITY variables, and running notify-send with "sudo -u", all without ...
11
votes
2answers
11k views

Bash Script on Startup? (Linux)

Is there any way to make/run a bash script on reboot (like in Debian/Ubuntu for instance, since thats what my 2 boxes at home have) Also, any recommended guides for doing cron jobs? I'm completely ...
5
votes
3answers
15k views

executing a sh script from the cron

I have a test.sh script #!/bin/sh php /home/v/file.php sh /root/x/some.sh when I execute the file as root from command line it works. sh /home/v/test.sh when I set it to crontab -e (is the root ...
18
votes
4answers
1k views

Path independent shebangs

I have a script that I want to be able to run in two machines. These two machines get copies of the script from the same git repository. The script needs to run with the right interpreter (e.g. zsh). ...
9
votes
2answers
1k views

Interactive shell with environment identical to cron

I am aware of a lot of pitfalls in the magic world of crontabs, but sometimes it would help troubleshooting a lot when you have some smart way to enter an interactive (bash) shell with exact identical ...
19
votes
2answers
74k views

crontab's @reboot only works for root?

man 5 crontab is pretty clear on how to use crontab to run a script on boot: These special time specification "nicknames" are supported, which replace the 5 initial time and date fields, and ...
15
votes
1answer
18k views

Why does cron silently fail to run sudo stuff in my script?

I have a script run from a non-privileged users' crontab that invokes some commands using sudo. Except it doesn't. The script runs fine but the sudo'ed commands silently fail. The script runs ...
2
votes
2answers
8k views

Run a GUI program at startup

I am using Ubuntu 14.04. I wrote a small script named trial. The contents of the script are as follows: #!/bin/sh SHELL=/bin/sh PATH=/bin:/sbin:/usr/bin:/usr/sbin sh -c firefox I copied the ...
1
vote
1answer
358 views

Keeping track of service status continuously

I need to monitor the status of nagios service (Because, whenever I make any changes in configuration and apply the new configuration, I would find nagios service stopped). If found in 'stopped' ...
34
votes
15answers
6k views

Run unix command precisely at very short intervals WITHOUT accumulating time lag over time

Question I'd like to be able to run a UNIX command precisely every second over a long time period. I need a solution, which does not lag behind after a certain time, because of the time the command ...
63
votes
4answers
59k views

What is the 'working directory' when cron executes a job

I have a script that works when I run it from the command line, but when I schedule it with cron I get errors that it cannot find files or commands. My questions is twofold: When I schedule a cron ...
7
votes
4answers
25k views

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?
13
votes
2answers
15k views

cron ignores variables defined in “.bashrc” and “.bash_profile”

I have defined "SHELL" variable in /etc/crontab file: [martin@martin ~]$ grep SHELL /etc/crontab SHELL=/usr/local/bin/bash [martin@martin ~]$ file /usr/local/bin/bash /usr/local/bin/bash: ELF 32-bit ...
7
votes
1answer
2k views

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 ...
6
votes
3answers
5k views

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 ...
4
votes
1answer
3k views

Automatically detect when a file has reached a size limit

I would like to send an email when a file reach a certain size limit. The only way I thought of doing this is by doing a cronjob which will check the file size and send the email if the file is ...
1
vote
1answer
4k views

Run gui application on startup

I can run a script at boot by adding the following line to my crontab: @reboot perl /path/script That works fine. But the problem arises when I try to run a gui application such as gmail notify. It ...
56
votes
8answers
121k views

Where are cron errors logged?

If I setup cron jobs incorrectly they appear to silently fail. Where should I look for an error log to understand what went wrong?
20
votes
5answers
41k views

Using the system date / time in a Cron Script

I'm setting up a Cronjob that will backup a MySQL database I have in my server, but I don't want it to keep overwriting the same file over and over again. Instead, I want to have an array of backups ...
11
votes
2answers
28k views

Crontab job start +1 min after @reboot

Need a script executed at each reboot in +1 minute. I placed a record @reboot but it is too early for my script. How to execute it sometime after reboot?
7
votes
2answers
39k 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 ...
15
votes
3answers
17k views

Does RHEL/CentOS execute all cronjob files under /etc/cron.d/*, or just some of them?

This is a Red Hat Enterprise Linux 5 system (RHEL). We manage this system using CFengine. We have several cronjobs which are running twice as often as usual. I checked the cronjobs under /etc/cron.d/ ...
6
votes
2answers
5k views

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.
6
votes
1answer
6k views

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 ...
4
votes
4answers
9k views

Installing crontab using bash script

I have created a script to install two scripts on to the crontab. #!/bin/bash sudo crontab -l > mycron #echo new cron into cron file echo "*/05 * * * * bash ...
4
votes
2answers
3k views

How to access X display from a cron job when using gdm3? [duplicate]

Possible Duplicate: Open a window on a remote X display (why “Cannot open display”)? I'm trying to run a cron job that needs access to my X session. I know my X session will ...
2
votes
1answer
762 views

Check for process already running in webfaction?

I use Django framework on webfaction and have 5 different cron jobs. One of them lasts much longer than others and sometimes gets stuck (30-120 seconds or more). I have already set that cron job to ...
1
vote
1answer
2k views

Pimp rsyslogd to have less i/o (cron, pam,…) and less logging

On my raspberry I really don't need crons and pam logging and I want to have less i/o to make the SD card life a little longer.. I have already removed cron with the second line cron.none, I'm ...
3
votes
3answers
5k views

Cron job to check if PHP script is running, if not then run

I am wondering if someone might point me in the right direction. I've got little experience working with the Linux command line and recently due to various factors in work I've been required to gain ...
2
votes
2answers
181 views

Cron only occasionally sends e-mail on output and errors

On Debian 8.1, I'm using a Bash feature to detect whether the stackoverflow.com website is reachable: (echo >/dev/tcp/stackoverflow.com/80) &>/dev/null || echo "stackoverflow unreachable" This is ...
2
votes
4answers
804 views

Calling scripts from inside other scripts

I have a script which I call every 10 minutes with a cronjob: */10 * * * * ~/mydirectory/myscript.sh Now, inside ~/mydirectory there is also another script, let's say myotherscript.sh which I'd ...
2
votes
1answer
8k views

Why isn't this crontab job running

I have a cron job that runs every minute on an Ubuntu 12.04 box $sudo crontab -e * * * * * mylogin /pathto/file.sh > /log/filelog If I run file.sh, the bash script does some stuff and echos out ...
2
votes
1answer
2k views

Cron does not print to syslog

I have following crontab file - # /etc/crontab: system-wide crontab # Unlike any other crontab you don't have to run the `crontab' # command to install the new version when you edit this file # and ...
1
vote
3answers
5k views

Using nohup to keep a script running indefinitely

I am very new to Linux and I've only been using it to SSH to my web server using Putty. The issue I am having is this: Basically I've got 2 php scripts. One get_tweets.php constantly listens for ...
0
votes
2answers
185 views

Not all shell scripts working with crontab

I know this is a pretty broad title but I didn't know what to start with. Anyway, straight to the point. I have a little VPS I run apache and a Minecraft server on. I don't ever turn it off, but ...
39
votes
3answers
158k views

How can get a list of all scheduled cron jobs on my machine?

My sysadmin has set up a bunch of cron jobs on my machine. I'd like to know exactly what is scheduled for what time. How can I get that list?
37
votes
9answers
70k views

How can I run a cron command with existing environmental variables?

How can I run a cron command with existing environmental variables? If I am at a shell prompt I can type echo $ORACLE_HOME and get a path. This is one of my environmental variables that gets set in ...
32
votes
4answers
68k views

How do I completely silence a cronjob to /dev/null/?

On my Ubuntu-Desktop and on my debian-server I have a script which needs to be executed each minute (a script that calls the minute-tic of my space online browsergame). The problem is that on ...
15
votes
7answers
724 views

How to Find a Fugitive Crontab

A few years ago I setup a cron job to automatically ping a URL every minute as part of a monitoring system (that's oversimplification, but it'll do for this question). Because I'm a horrible person, I ...
10
votes
6answers
3k views

CronJob every 25 minutes

I want to know whether there is any easier way to run a job every 25 minutes. In cronjob, if you specify the minute parameter as */25, it'll run only on 25th and 50th minute of every hour
19
votes
1answer
55k views

How to redirect output to a file from within cron?

I have a backup script which I need to run at a particular time of a day so I am using cron for this task and from within cron am also trying to redirect the output of backup script to a logfile. ...
9
votes
5answers
8k views

Run script in a non interactive shell?

I have a cron job that is running a script. When I run the script via an interactive shell (ssh'ed to bash) it works fine. When the script runs by itself via cron it fails. My guess is that it is ...
7
votes
2answers
6k views

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 ...
8
votes
2answers
10k views

Not able to ssh in to remote machine using shell script in Crontab

Below is the script which i am trying to run, which runs without any issue for i in `seq 200 2100` do usr=(`ssh -t -t -o ConnectTimeout=60 machine$1 finger | tail -1 | awk '{print$1}'`) echo ...
7
votes
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/*)
3
votes
3answers
604 views

Automating tasks on a website on a headless server

I want to automate a task which can only be done on a website (with prior login) on my debian server. There is no public API available, so I can't use one. Is there a way to do so? I thought about a ...
3
votes
2answers
472 views

I need help with a cronjob to watch for runaway processes and kill them

I have an interesting situation, I have a runaway ruby process - I know exactly how I trigger it. Point is, it got me thinking about runaway processes (CPU usage or memory usage). How would one ...
2
votes
1answer
243 views

To write this Pseudocode with Regex

I am doing a Makefile which I run regularly by Crontab every day at 0230 crontab -e; 30 2 * * * /bin/thePseudocode Python-like Pseudocode directories = ["Cardiology", "Rheumatology", "Surgery"] ...