Questions tagged [cron]

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

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81
votes
4answers
139k views

Open a window on a remote X display (why “Cannot open display”)?

Once upon a time, DISPLAY=:0.0 totem /path/to/movie.avi after ssh 'ing into my desktop from my laptop would cause totem to play movie.avi on my desktop. Now it gives the error: No protocol ...
121
votes
6answers
99k 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 ...
32
votes
12answers
20k 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 ...
66
votes
13answers
58k 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. ...
4
votes
3answers
14k 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 ...
18
votes
4answers
89k 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?
12
votes
2answers
14k 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 ...
13
votes
3answers
15k views

What's wrong with these two cron jobs?

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 --date='...
136
votes
6answers
366k views

What does '>/dev/null 2>&1' mean in this article of crontab basics? [duplicate]

I am reading an article about crontab There is something about disabling automatically sending emails. Disable Email By default cron jobs sends an email to the user account executing the ...
65
votes
8answers
330k 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 ...
5
votes
2answers
8k views

Why can't cron job find basic Linux commands? [closed]

I'm trying to set up a cron job to run a PHP script daily as part of a web-based booking system. It's been running perfectly for several years on a different Apache server using this in the crontab: ...
118
votes
11answers
231k 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 ...
107
votes
2answers
226k 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. ...
47
votes
3answers
133k 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?
53
votes
8answers
53k 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 ...
34
votes
2answers
11k views

Where is cron's PATH set?

Cron doesn't use the path of the user whose crontab it is and, instead, has its own. It can easily be changed by adding PATH=/foo/bar at the beginning of the crontab, and the classic workaround is to ...
10
votes
2answers
27k 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.
10
votes
2answers
3k 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 ...
12
votes
3answers
60k 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 ...
11
votes
1answer
15k views

How are files under /etc/cron.d used?

How are files under /etc/cron.d used? From https://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/ cron reads the files in /etc/cron.d/ directory. Usually system daemon ...
-1
votes
2answers
340 views

how to properly log the output of a console program that frequently updates “parts” of the screen, resulting in a messy log file?

I have some Java executable (jar) that is run my some shell script from a cron job once every night. That executable does not print log statements "as usual" just by printing them out in a sequential ...
175
votes
7answers
184k 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 question is twofold: When I schedule a cron ...
175
votes
9answers
384k 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?
17
votes
4answers
35k views

how to set crontab PATH variable

I had a problem running a script from crontab. After some research I understood the problem was because PATH parameter doesn't include /sbin. I looked what it does include in /etc/crontab: PATH=/...
30
votes
1answer
38k 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 ...
20
votes
4answers
2k 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). ...
1
vote
3answers
10k views

BashScript works from Terminal but not from CronTab

I've got a bunch of CronJobs, and they work fine, except for one. I've looked through a lot of forums and websites, and tried a combination of things but alas nothing has worked. Rephrasing the ...
4
votes
1answer
3k views

tput: No value for $TERM and no -T specified

I am trying to run a bash script I have via cron, and I am getting the following error at the beginning of the execution: tput: No value for $TERM and no -T specified Here is what is in my crontab: ...
2
votes
1answer
2k 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' state,...
74
votes
4answers
187k 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 ...
38
votes
15answers
10k 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 ...
72
votes
1answer
60k views

How to change cron shell (sh to bash)?

Is it possible to make commands in crontab run with bash instead of sh? I know you can pass commands to bash with -c, but that's annoying and I never use sh anyway.
45
votes
4answers
52k views

How can I tell cron to run a command every other day (odd/even)

When configuring cron to run a command every other day using the "Day of Month" field, like so: 1 22 */2 * * COMMAND it runs every time the day of month is odd: 1,3,5,7,9 and so on. How can I ...
12
votes
6answers
7k 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
3
votes
4answers
11k views

How to display a (zenity/GUI) dialog to the user after a root cron task has completed

I have a simple periodic cron task that must run as root. I want to use Zenity (or similar) to display a GUI informational dialog to user 1000 (or logged in user or all users) when the cron task ...
12
votes
5answers
11k views

command not running in cron (systemctl suspend)

I have this cronjob set : * * * * * /usr/bin/systemctl suspend And it is not working. But I can run it in a shell and it works. I don't understand what could be not working. EDIT Redirecting error ...
10
votes
4answers
29k 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 /mnt/md0/capture/delete_old_pcap....
14
votes
2answers
55k views

What are the runtime permissions of a cron job?

When a cron job runs with what privilege does it execute? I'm not sure about that. Is it with the same privileges of the user that added it via crontab -e?
6
votes
2answers
4k 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 always be ...
3
votes
2answers
12k 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 ...
1
vote
1answer
2k views

Differences between `/etc/crontab`, files under `/etc/cron.d/` and `/var/spool/cron/crontabs/root`?

What is the difference between the purposes of /etc/crontab files under /etc/cron.d/ /var/spool/cron/crontabs/root If you want to add a cron job, into which file would you add it? manpage of cron(...
4
votes
1answer
15k 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
3answers
1k 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 ...
0
votes
1answer
1k views

What is causing my “Unexpected EOF Error while looking for …” error? [duplicate]

I am getting an issue while running a cron job for exporting all databases on my Godaddy Shared hosting Cpanel account. But I have trouble finding the syntax error in below command. Same command is ...
0
votes
2answers
59 views

Replace log file without affecting “Redirection of stdin and stdout” using nohup

production.log [2019-02-11 10:18:18] GET / [2019-02-11 11:18:19] POST blavadasdasdgd ... ... <--- A lot of in between logs and other data ... [2019-02-12 11:18:20] INFO ::HTTPServer#start: pid=...
213
votes
3answers
501k 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?
84
votes
2answers
32k views

Cron vs systemd timers

It was recently pointed out to me that an alternative to cron exists, namely systemd timers. However, I know nothing about systemd or systemd timers. I have only used cron. There is a little ...
49
votes
3answers
124k views

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 ...
22
votes
5answers
167k views

How do I create a service for a shell script so I can start and stop it like a daemon?

I'm using CentOS 7 what my aim is to create a cron for every five seconds but as I researched we can use cron only for a minute so what I am doing now is I have created a shell file. hit.sh while ...
143
votes
6answers
292k views

how can I make cron run a job right now, for testing/debugging? without changing the schedule!

I have a cron job that is scheduled to run everyday, other than changing the schedule, is there any other way to do a test run of the command right now to see if it works as intended? EDIT: (from ...