I have set up a cronjob for root user in ubuntu environment as follows by typing crontab -e
34 11 * * * sh /srv/www/live/CronJobs/daily.sh
0 08 * * 2 sh /srv/www/live/CronJobs/weekly.sh
0 08 1 * * sh /srv/www/live/CronJobs/monthly.sh
But the cronjob does not run. I have tried checking if the cronjob is running using pgrep cron and that gives process id 3033. The shell script calls a python file and is used to send an email. Running the python file is ok. There's no error in it but the cron doesn't run. The daily.sh file has the following code in it.
python /srv/www/live/CronJobs/daily.py
python /srv/www/live/CronJobs/notification_email.py
python /srv/www/live/CronJobs/log_kpi.py
WTF?! My cronjob doesn't run?!
Here's a checklist guide to debug not running cronjobs:
Is the Cron daemon running?
Run ps ax | grep cron and look for cron.
Debian: service cron start or service cron restart
Is cron working?
* * * * * /bin/echo "cron works" >> /tmp/file
Syntax correct? See below.
You obviously need to have write access to the file you are redirecting the output to. A unique file name in /tmp which does not currently exist should always be writable.
Probably also add 2>&1 to include standard error as well as standard output, or separately output standard error to another file with 2>>/tmp/errors
Is the command working standalone?
Check if the script has an error, by doing a dry run on the CLI
When testing your command, test as the user whose crontab you are editing, which might not be your login or root
Can cron run your job?
Check /var/log/cron.log or /var/log/messages for errors.
Ubuntu: grep CRON /var/log/syslog
Redhat: /var/log/cron
Check permissions
Set executable flag on the command: chmod +x /var/www/app/cron/do-stuff.php
If you redirect the output of your command to a file, verify you have permission to write to that file/directory
Check paths
Check she-bangs / hashbangs line
Do not rely on environment variables like PATH, as their value will likely not be the same under cron as under an interactive session. See How to get CRON to call in the correct PATHs
Don't suppress output while debugging
Commonly used is this suppression: 30 1 * * * command > /dev/null 2>&1
Re-enable the standard output or standard error message output by removing >/dev/null 2>&1 altogether; or perhaps redirect to a file in a location where you have write access: >>cron.out 2>&1 will append standard output and standard error to cron.out in the invoking user's home directory.
If you don't redirect output from a cron job, the daemon will try to send you any output or error messages by email. Check your inbox (maybe simply more $MAIL if you don't have a mail client). If mail is not available, maybe check for a file named dead.letter in your home directory, or system log entries saying that the output was discarded. Especially in the latter case, probably edit the job to add redirection to a file, then wait for the job to run, and examine the log file for error messages or other useful feedback.
If you are trying to figure out why something failed, the error messages will be visible in this file. Read it and understand it.
Still not working? Yikes!
Raise the cron debug level
Debian
in /etc/default/cron
set EXTRA_OPTS="-L 2"
service cron restart
tail -f /var/log/syslog to see the scripts executed
Ubuntu
in /etc/rsyslog.d/50-default.conf
add or comment out line cron.* /var/log/cron.log
reload logger sudo /etc/init.d/rsyslog restart
re-run cron
open /var/log/cron.log and look for detailed error output
Reminder: deactivate log level, when you are done with debugging
Run cron and check log files again
Cronjob Syntax
# Minute Hour Day of Month Month Day of Week User Command
# (0-59) (0-23) (1-31) (1-12 or Jan-Dec) (0-6 or Sun-Sat)
0 2 * * * root /usr/bin/find
This syntax is only correct for the root user. Regular user crontab syntax doesn't have the User field (regular users aren't allowed to run code as any other user);
# Minute Hour Day of Month Month Day of Week Command
# (0-59) (0-23) (1-31) (1-12 or Jan-Dec) (0-6 or Sun-Sat)
0 2 * * * /usr/bin/find
Crontab Commands
crontab -l
Lists all the user's cron tasks.
crontab -e, for a specific user: crontab -e -u agentsmith
Starts edit session of your crontab file.
When you exit the editor, the modified crontab is installed automatically.
crontab -r
Removes your crontab entry from the cron spooler, but not from crontab file.
Another reason crontab will fail: Special handling of the % character.
From the manual file:
The entire command portion of the line, up to a newline or a
"%" character, will be executed by /bin/sh or by the shell specified
in the SHELL variable of the cronfile. A "%" character in the
command, unless escaped with a backslash (\), will be changed into
newline characters, and all data after the first % will be sent to
the command as standard input.
In my particular case, I was using date --date="7 days ago" "+%Y-%m-%d" to produce parameters to my script, and it was failing silently. I finally found out what was going on when I checked syslog and saw my command was truncated at the % symbol. You need to escape it like this:
date --date="7 days ago" "+\%Y-\%m-\%d"
See here for more details:
http://www.ducea.com/2008/11/12/using-the-character-in-crontab-entries/
Finally I found the solution. Following is the solution:-
Never use relative path in python scripts to be executed via crontab.
I did something like this instead:-
import os
import sys
import time, datetime
CLASS_PATH = '/srv/www/live/mainapp/classes'
SETTINGS_PATH = '/srv/www/live/foodtrade'
sys.path.insert(0, CLASS_PATH)
sys.path.insert(1,SETTINGS_PATH)
import other_py_files
Never supress the crontab code instead use mailserver and check the mail for the user. That gives clearer insights of what is going.
I want to add 2 points that I learned:
Cron config files put in /etc/cron.d/ should not contain a dot (.). Otherwise, it won't be read by cron.
If the user running your command is not in /etc/shadow. It won't be allowed to schedule cron.
Refs:
http://manpages.ubuntu.com/manpages/xenial/en/man8/cron.8.html
https://help.ubuntu.com/community/CronHowto
To add another point, a file in /etc/cron.d must contain an empty new line at the end. This is likely related to the response by Luciano which specifies that:
The entire command portion of the line, up to a newline or a "%"
character, will be executed
I found useful debugging information on an Ubuntu 16.04 server by running:
systemctl status cron.service
In my case I was kindly informed I had left a comment '#' off of a remark line:
Aug 18 19:12:01 is-feb19 cron[14307]: Error: bad minute; while reading /etc/crontab
Aug 18 19:12:01 is-feb19 cron[14307]: (*system*) ERROR (Syntax error, this crontab file will be ignored)
It might also be a timezone problem.
Cron uses the local time.
Run the command timedatectl to see the machine time and make sure that your crontab is in this same timezone.
https://askubuntu.com/a/536489/1043751
I had a similar problem to the link below.
similar to my problem
my original post
My Issue
My issue was that cron / crontab wouldn't execute my bash script. that bash script executed a python script.
original bash file
#!/bin/bash
python /home/frosty/code/test_scripts/test.py
python file (test.py)
from datetime import datetime
def main():
dt_now = datetime.now()
string_now = dt_now.strftime('%Y-%m-%d %H:%M:%S.%f')
with open('./text_file.txt', 'a') as f:
f.write(f'wrote at {string_now}\n')
return None
if __name__ == '__main__':
main()
the error I was getting
File "/home/frosty/code/test_scripts/test.py", line 7
string_to_write = f'wrote at {string_now}\n'
^
SyntaxError: invalid syntax
this error didn't make sense because the code executed without error from the bash file and the python file.
** Note -> ensure in the crontab -e file you don't suppress the output. I sent the output to a file by adding >>/path/to/cron/output/file.log 2>&1 after the command. below is my crontab -e entry
*/5 * * * * /home/frosty/code/test_scripts/echo_message_sh >>/home/frosty/code/test_scripts/cron_out.log 2>&1
the issue
cron was using the wrong python interpreter, probably python 2 from the syntax error.
how I solved the problem
I changed my bash file to the following
#!/bin/bash
conda_shell=/home/frosty/anaconda3/etc/profile.d/conda.sh
conda_env=base
source ${conda_shell}
conda activate ${conda_env}
python /home/frosty/code/test_scripts/test.py
And I changed my python file to the following
from datetime import datetime
def main():
dt_now = datetime.now()
string_now = dt_now.strftime('%Y-%m-%d %H:%M:%S.%f')
string_file = '/home/frosty/code/test_scripts/text_file.txt'
string_to_write = 'wrote at {}\n'.format(string_now)
with open(string_file, 'a') as f:
f.write(string_to_write)
return None
if __name__ == '__main__':
main()
No MTA installed, discarding output
I had a similar problem with a PHP file executed as a CRON job.
When I manually execute the file it works, but not with CRON tab.
I got the output message: "No MTA installed, discarding output"
Postfix is the default Mail Transfer Agent (MTA) in Ubuntu and can be installed it using
sudo apt-get install postfix
But this same message can be also output when you add a log file as below and it does not have proper write permission to /path/to/logfile.log
/path/to/php -f /path/to/script.php >> /path/to/logfile.log
The permission issue can occur if you create the cron-log file manually using a command like touch while you are logged in as a different user and you add CRONs in the tab of another user(group) like www-data using: sudo crontab -u www-data -e. Then CRON daemon tries to write to the log file and fail, then tries to send the output as an email using Ubuntu's MTA and when it's not found, outputs "No MTA installed, discarding output".
To prevent this:
Create the file with proper permission.
Avoid creating the relevant CRON log file manually, add the log in CRON tab and let the log file get created automatically when the cron is run.
I've found another reason for user's crontab not running: the hostname is not present on the hosts file:
user#ubuntu:~$ cat /etc/hostname
ubuntu
Now the hosts file:
user#ubuntu:~$ cat /etc/hosts
127.0.0.1 localhost
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
This is on a Ubuntu 14.04.3 LTS, the way to fix it is adding the hostname to the hosts file so it resembles something like this:
user#ubuntu:~$ cat /etc/hosts
127.0.0.1 ubuntu localhost
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
For me, the solution was that the file cron was trying to run was in an encrypted directory, more specifcically a user diretory on /home/. Although the crontab was configured as root, because the script being run exisited in an encrypted user directory in /home/ cron could only read this directory when the user was actually logged in. To see if the directory is encrypted check if this directory exists:
/home/.ecryptfs/<yourusername>
if so then you have an encrypted home directory.
The fix for me was to move the script in to a non=encrypted directory and everythig worked fine.
As this is becoming a canonical for troubleshooting cron issues, allow me to add one specific but rather complex issue: If you are attempting to run a GUI program from cron, you are probably Doing It Wrong.
A common symptom is receiving error messages about DISPLAY being unset, or the cron job's process being unable to access the display.
In brief, this means that the program you are trying to run is attempting to render something on an X11 (or Wayland etc) display, and failing, because cron is not attached to a graphical environment, or in fact any kind of input/output facility at all, beyond being able to read and write files, and send email if the system is configured to allow that.
For the purposes of "I'm unable to run my graphical cron job", let's just point out in broad strokes three common scenarios for this problem.
Probably identify the case you are trying to implement, and search for related questions about that particular scenario to learn more, and find actual solutions with actual code.
If you are trying to develop an interactive program which communicates with a user, you want to rethink your approach. A common, but nontrivial, arrangement is to split the program in two: A back-end service which can run from cron, but which does not have any user-visible interactive facilities, and a front-end client which the user runs from their GUI when they want to communicate with the back-end service.
Probably your user client should simply be added to the user(s)' GUI startup script if it needs to be, or they want to, run automatically when they log in.
I suppose the back-end service could be started from cron, but if it requires a GUI to be useful, maybe start it from the X11 server's startup scripts instead; and if not, probably run it from a regular startup script (systemd these days, or /etc/rc.local or a similar system startup directory more traditionally).1
If you are trying to run a GUI program without interacting with a real user 2, you may be able to set up a "headless" X11 server 3 and run a cron job which starts up that server, runs your job, and quits.
Probably your job should simply run a suitable X11 server from cron (separate from any interactive X11 server which manages the actual physical display(s) and attached graphics card(s) and keyboard(s) available to the system), and pass it a configuration which runs the client(s) you want to run once it's up and running. (See also the next point for some practical considerations.)
You are running a computer for the sole purpose of displaying a specific application in a GUI, and you want to start that application when the computer is booted.
Probably your startup scripts should simply run the GUI (X11 or whatever) and hook into its startup script to also run the client program once the GUI is up and running. In other words, you don't need cron here; just configure the startup scripts to run the desktop GUI, and configure the desktop GUI to run your application as part of the (presumably automatic, guest?) login sequence.4
There are ways to run X11 programs on the system's primary display (DISPLAY=:0.0) but doing that from a cron job is often problematic, as that display is usually reserved for actual interactive use by the first user who logs in and starts a graphical desktop. On a single-user system, you might be able to live with the side effects if that user is also you, but this tends to have inconvenient consequences and scale very poorly.
An additional complication is deciding which user to run the cron job as. A shared system resource like a back-end service can and probably should be run by root (though ideally have a dedicated system account which it switches into once it has acquired access to any privileged resources it needs) but anything involving a GUI should definitely not be run as root at any point.
A related, but distinct problem is to interact in any meaningful way with the user. If you can identify the user's active session (to the extent that this is even well-defined in the first place), how do you grab their attention without interfering with whatever else they are in the middle of? But more fundamentally, how do you even find them? If they are not logged in at all, what do you do then? If they are, how do you determine that they are active and available? If they are logged in more than once, which terminal are they using, and is it safe to interrupt that session? Similarly, if they are logged in to the GUI, they might miss a window you spring up on the local console, if they are actually logged in remotely via VNC or a remote X11 server.
As a further aside: On dedicated servers (web hosting services, supercomputing clusters, etc) you might even be breaking the terms of service of the hosting company or institution if you install an interactive graphical desktop you can connect to from the outside world, or even at all.
1
The #reboot hook in cron is a convenience for regular users who don't have any other facility for running something when the system comes up, but it's just inconvenient and obscure to hide something there if you are root anyway and have complete control over the system. Use the system facilities to launch system services.
2
A common use case is running a web browser which needs to run a full GUI client, but which is being controlled programmatically and which doesn't really need to display anything anywhere, for example to scrape sites which use Javascript and thus require a full graphical browser to render the information you want to extract.
Another is poorly designed scientific or office software which was not written for batch use, and thus requires a GUI even when you just want to run a batch job and then immediately quit without any actual need to display anything anywhere.
(In the latter case, probably review the documentation to check if there isn't a --batch or --noninteractive or --headless or --script or --eval option or similar to run the tool without the GUI, or perhaps a separate utility for noninteractive use.)
3
Xvfb is the de facto standard solution; it runs a "virtual framebuffer" where the computer can spit out pixels as if to a display, but which isn't actually connected to any display hardware.
4
There are several options here.
The absolutely simplest is to set up the system to automatically log in a specific user at startup without a password prompt, and configure that user's desktop environment (Gnome or KDE or XFCE or what have you) to run your script from its "Startup Items" or "Login Actions" or "Autostart" or whatever the facility might be called. If you need more control over the environment, maybe run bare X11 without a desktop environment or window manager at all, and just run your script instead. Or in some cases, maybe replace the X11 login manager ("greeter") with something custom built.
The X11 stack is quite modular, and there are several hooks in various layers where you could run a script either as part of a standard startup process, or one which completely replaces a standard layer. These things tend to differ somewhat between distros and implementations, and over time, so this answer is necessarily vague and incomplete around these matters. Again, probably try to find an existing question about how to do things for your specific platform (Ubuntu, Raspbian, Gnome, KDE, what?) and scenario. For simple scenarios, perhaps see Ubuntu - run bash script on startup with visible terminal
I experienced same problem where crons are not running.
We fixed by changing permissions and owner by
Crons made root owner as we had mentioned in crontab AND
Cronjobs 644 permission given
There is already a lot of answers, but none of them helped me so I'll add mine here in case it's useful for somebody else.
In my situation, my cronjobs were working find until there was a power shortage that cut the power to my Raspberry Pi. Cron got corrupted. I think it was running a long python script exactly when the shortage happened. Nothing in the main answer above worked for me. The solution was however quite simple. I just had to force reinstallation of cron with:
sudo apt-get --reinstall install cron
It work right away after this.
Copying my answer for a duplicated question here.
cron may not know where to find the Python interpreter because it doesn't share your user account's environment variables.
There are 3 solutions to this:
If Python is at /usr/bin/python, you can change the cron job to use an absolute path: /usr/bin/python /srv/www/live/CronJobs/daily.py
Alternatively you can also add a PATH value to the crontab with PATH=/usr/bin.
Another solution would be to specify an interpreter in the script file, make it executable, and call the script itself in your crontab:
a. Put shebang at the top of your python file: #!/usr/bin/python.
b. Set it to executable: $ chmod +x /srv/www/live/CronJobs/daily.py
c. Put it in crontab: /srv/www/live/CronJobs/daily.py
Adjust the path to the Python interpreter if it's different on your system.
Reference
CRON uses a different TIMEZONE
A very common issue is: cron time settings may is different than your. In particular, the timezone could be not be the same:
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
You can run:
* * * * * echo $(date) >> /tmp/test.txt
This should generate a file like:
# cat test.txt
Sun 03 Apr 2022 09:02:01 AM UTC
Sun 03 Apr 2022 09:03:01 AM UTC
Sun 03 Apr 2022 09:04:01 AM UTC
Sun 03 Apr 2022 09:05:01 AM UTC
Sun 03 Apr 2022 09:06:01 AM UTC
If you are using a TZ other than UTC, you can try:
timedatectl set-timezone America/Sao_Paulo
replace America/Sao_Paulo according to you settings.
I'm not sure if it is actually necessary, but you can run:
sudo systemctl restart cron.service
After that, cron works as I expected:
# cat test.txt
Sun 03 Apr 2022 09:02:01 AM UTC
Sun 03 Apr 2022 09:03:01 AM UTC
Sun 03 Apr 2022 09:04:01 AM UTC
Sun 03 Apr 2022 09:05:01 AM UTC
Sun 03 Apr 2022 09:06:01 AM UTC
Sun 03 Apr 2022 09:07:01 AM UTC
Sun 03 Apr 2022 09:08:01 AM UTC
Sun 03 Apr 2022 09:09:01 AM UTC
Sun 03 Apr 2022 09:10:01 AM UTC
Sun 03 Apr 2022 06:11:01 AM -03
Sun 03 Apr 2022 06:12:01 AM -03
Sun 03 Apr 2022 06:13:01 AM -03
Sun 03 Apr 2022 06:14:01 AM -03
Try
service cron start
or
systemctl start cron
In my case I was trying to run cron locally.
I checked status:
service cron status
It showed me:
* cron is not running
Then I simply started the service:
service cron start
Sometimes the command that cron needs to run is in a directory where cron has no access, typically on systems where users' home directories' permissions are 700 and the command is in that directory.
Although answer has been accepted for this question, I will like to add what worked for me.
it's a good idea to quote the URL, if it contains a query it may not work without everything being quoted.
DONT FORGET TO PUT YOUR URL WHICH CONTAINS "?, =, #, %" IN A QUOTE.
Example.
https://paystack.com/indexphp?docs/api/#transaction-charge-authorization&date=today
should be in a quote like so
"https://paystack.com/indexphp?docs/api/#transaction-charge-authorization&date=today"
I am trying to make the at bash command to run, but it is not working for me. I can add a job to the queue, but it is not run when the time is up. What am I doing wrong?
hpek#melda:~$ cat /usr/lib/cron/at.deny
hpek#melda:~$ atq
hpek#melda:~$ at now +2 minutes
echo TTTEEEST
job 12 at Sun May 6 02:09:00 2012
hpek#melda:~$ date
Sun May 6 02:10:24 CEST 2012
hpek#melda:~$ atq
12 Sun May 6 02:09:00 2012
hpek#melda:~$
UPD2021.08.06 atd was removed in MacOS 11.5.2 (or earlier)
$ sudo find / -name atd -print 2>/dev/null
$
It is working fine. It's just that commands running with at don't write their output to the terminal that you called it from.
Try:
at now +2 minutes
echo TTTEEEST > new_file_test
You'll see the file appear in two minutes.
Take a look at /var/at/jobs and see if your at jobs are listed there. (It may be a different directory based upon OS).
By default, at isn't enabled on most systems. In order for at jobs to actually get executed, the atrun command must execute.
This command is executed either through launchd or through the cron depending upon the system.
The exact mechanisms are different from system to system, so you'll have to read all the various manpages on at, atrun, etc. to verify if at is really enabled on your system, and whether you have permissions to run at jobs. There's normally both an ant allow and an ant deny file on your system, so you need to check both. You must be both in the allowed file, and also not in the deny file.
On top of that, you have to make sure that at is even enabled on your system (due to security concerns, it is usually disabled).
Check your mail:
An at - or batch - command invoked from a su(1) shell will
retain the current userid. The user will be mailed standard
error and standard output from his commands, if any. Mail
will be sent using the command /usr/sbin/sendmail. If at is
executed from a su(1) shell, the owner of the login shell
will receive the mail.
I've found this here
First make sure that the at daemon is running using a command like this:
# ps -ef | grep atd
root 8231 1 0 18:10 ? 00:00:00 /usr/sbin/atd
If you don’t see atd running start it with this command:
# /etc/init.d/atd start
To analyze at(d) execution problems it may help to
Check /etc/at.allow and /etc/at.deny for existance and contents (see man at.allow)
Check owner and access rights of the atd spool directory
(/var/spool/cron/atjobs, daemon:daemon, 770 on Ubuntu)
Check if atd daemon is running (systemctrl -a | grep atd on Ubuntu)
tail -f /var/log/syslog (at execution time)
journalctl -b | grep atd (found that here, contains further hints)
The "Permission denied" error may also be caused by limited number of logins defined (for the at running user) in /etc/security/limits.conf.
I too faced same issue with echo when used along with at command. But if you try to redirect the output using > or >> then it works perfectly. Also try some other system commands like reboot, ls > some_text_file etc to make sure at command is working. Else try
sudo systemctl enable --now atd to enable at daemon
Conclution First:
atrun or atd daemon is not running, causing this problem.
Guideline to solve your case:
check at mannul by man at first.
In my case, I(macos 10.13.6) found following info:
Note that at is implemented through the launchd(8) daemon periodically invoking atrun(8), which is disabled by default. See atrun(8) for information about enabling atrun.
check atrun mannul by man atrun, I found :
The atrun utility runs commands queued by at(1). It is invoked periodically by launchd(8) as specified in the com.apple.atrun.plist property list. By default the property list contains the
Disabled key set to true, so atrun is never invoked.
Execute the following command as root to enable atrun:
launchctl load -w /System/Library/LaunchDaemons/com.apple.atrun.plist
I am running Ubuntu 11.10 (Unity interface) and I created a Bash script that uses 'gnome-open' to open a series of web pages I use every morning. When I manually execute the script in the Terminal, the bash script works just fine. Here's a sample of the script (it's all the same so I've shortened it):
#!/bin/bash
gnome-open 'https://docs.google.com';
gnome-open 'https://mail.google.com';
Since it seemed to be working well, I added a job to my crontab (mine, not root's) to execute every weekday at a specific time.
Here's the crontab entry:
30 10 * * 1,2,3,4,5 ~/bin/webcheck.sh
The problem is this error gets returned for every single 'gnome-open' command in the bash script:
GConf-WARNING **: Client failed to connect to the D-BUS daemon:
Unable to autolaunch a dbus-daemon without a $DISPLAY for X11
GConf Error: No D-BUS daemon running
Error: no display specified
I did some searching to try and figure this out. The first thing I tried was relaunching the daemon using SIGHUP:
killall -s SIGHUP gconfd-2
That didn't work so I tried launching the dbus-daemon using this code from the manpage for dbus-launch:
## test for an existing bus daemon, just to be safe
if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
## if not found, launch a new one
eval `dbus-launch --sh-syntax --exit-with-session`
echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
fi
But that didn't do anything.
I tried adding simply 'dbus-launch' at the top of my bash script and that didn't work either.
I also tried editing the crontab to include the path to Bash, because I saw that suggestion on another thread but that didn't work.
Any ideas on how I can get this up and running?
Here is how the problem was solved. It turns out the issue was primarily caused by Bash not having access to an X window session (or at least that's how I understood it). So my problem was solved by editing my crontab like so:
30 10 * * 1,2,3,4,5 export DISPLAY=:0 && ~/bin/webcheck.sh
The "export DISPLAY=:0" statement told cron which display to use. I found the answer on this archived Ubuntu forum after searching for "no display specified" or something like that:
http://ubuntuforums.org/archive/index.php/t-105250.html
So now, whenever I'm logged in, exactly at 10:30 my system will automatically launch a series of webpages that I need to look at every day. Saves me having to go through the arduous process of typing in my three-letter alias every time :)
Glad you asked!
It depends on when it is run.
If the Gnome GDM Greeter is live, you can use the DBUS session from the logon dialog, if you will. You can, e.g., use this to send notifications to the logon screen, if no-one is logged in:
function do_notification
{
for pid in $(pgrep gnome-session); do
unset COOKIE
COOKIE="$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$pid/environ|cut -d= -f2-)"
GNUSER="$(ps --no-heading -o uname $pid)"
echo "Notifying user $GNUSER (gnome-session $pid) with '$#'"
sudo -u "$GNUSER" DBUS_SESSION_BUS_ADDRESS="$COOKIE" /usr/bin/notify-send -c "From CRON:" "$#"
done
unset COOKIE
}
As you can see the above code simply runs the same command (notify-send) on all available gnome-sessions, when called like:
do_notification "I wanted to let you guys know"
You can probably pick this apart and put it to use for your own purposes.
How do I get the name of the active user via the command line in OS X?
as 'whoami' has been obsoleted, it's probably more forward compatible to use:
id -un
If you'd like to display the full name (instead of the username), add the -F flag:
$ id -F
Andrew Havens
I'm pretty sure the terminal in OS X is just like unix, so the command would be:
whoami
I don't have a mac on me at the moment so someone correct me if I'm wrong.
NOTE - The whoami utility has been obsoleted, and is equivalent to id -un. It will give you the current user
whoami
EDIT
The whoami utility has been obsoleted by the id(1) utility, and is equivalent to id -un. The command id -p is suggested for normal interactive use.
Via here
Checking the owner of /dev/console seems to work well.
stat -f "%Su" /dev/console
There are two ways-
whoami
or
echo $USER
You can also use the logname command from the BSD General Commands Manual under Linux or MacOS to see the username of the user currently logged in, even if the user is performing a sudo operation. This is useful, for instance, when modifying a user's crontab while installing a system-wide package with sudo: crontab -u $(logname)
Per man logname:
LOGNAME(1)
NAME
logname -- display user's login name
If you want to know who's currently logged in to the system:
$ w
15:56:14 up 5 days, 20:58, 6 users, load average: 0.43, 0.53, 0.50
USER TTY LOGIN# IDLE JCPU PCPU WHAT
me pts/2 Fri19 1:03m 0.98s 0.98s -/bin/bash
me pts/3 09:55 6:00m 0.43s 0.43s /bin/bash
me pts/5 15:56 0.00s 0.23s 0.00s w
(This is from a Linux system; the formatting on OS X may be slightly different, but the information should be about the same.)
There may be multiple login sessions; UNIX is designed to be a multi-user system, after all.
The question has not been completely answered, IMHO. I will try to explain: I have a crontab entry that schedules a bash shell command procedure, that in turn does some cleanup of my files; and, when done, sends a notification to me using the OS X notification center (with the command osascript -e 'display notification ...). If someone (e.g. my wife or my daughter) switches the current user of the computer to her, leaving me in the background, the cron script fails when sending the notification.
So, Who is the current user means Has some other people become the effective user leaving me in the background? Do stat -f "%Su" /dev/console returns the current active user name?
The answer is yes; so, now my crontab shell script has been modified in the following way:
...
if [ "$(/usr/bin/stat -f ""%Su"" /dev/console)" = "loreti" ]
then /usr/bin/osascript -e \
'display notification "Cleanup done" sound name "sosumi" with title "myCleanup"'
fi
getting username in MAC terminal is easy...
I generally use whoami in terminal...
For example, in this case, I needed that to install Tomcat Server...
You can also retrieve it from the environment variables, but that is probably not secure, so I would go with Andrew's answer.
printenv USER
If you need to retrieve it from an app, like Node, it's easier to get it from the environment variables, such as
process.env.USER.
Define 'active user'.
If the question is 'who is the logged in user', then 'who am i' or 'whoami' is fine (though they give different answers - 'whoami' reports just a user name; 'who am i' reports on terminal and login time too).
If the question is 'which user ID is the effective ID for the shell', then it is often better to use 'id'. This reports on the real and effective user ID and group ID, and on the supplementary group IDs too. This might matter if the shell is running SUID or SGID.
you can open terminal and write down following command:
id -un
or
whoami
This will return your current login username.