在debian上通过crontab执行python脚本要疯了！

Question

This is what my crontab file looks like:

* * * * *  root /usr/bin/python /root/test.py >> /root/classwatch.log 2>&1

This is what my python script looks like:

#!/usr/bin/python
print "hello"

The cronjob creates the log file. But it is empty. I am also pretty certain that the python file is not being executed.

Appreciate any help! I've been playing with it for past 4 hrs with no luck.

Answer 1

There are two ways to create a crontab -- per user or globally. For the global crontab (/etc/crontab) you specify the user, as per:

# m h dom mon dow user  command
17  *   *   *   *   root        cd / && run-parts --report /etc/cron.hourly

For user crontabs you don't, as per:

aj@wherever:~$ crontab -l
0 * * * * /home/aj/bin/update-foobar

To get a python script running via #! notation, you just make the script executable (chmod 755 /root/test.py), and invoke it directly, something like:

/root/test.py

If you don't want to do that, you can run it via the python interpretor by hand, like:

/usr/bin/python /root/test.py

This assumes whichever user you're running as (ie the user in /etc/crontab, or the user you're running crontab -e as) has permission to see the python script -- /root might be inaccessible to regular users, eg.

You can get a good idea of whether your script is being executed at all by adding:

import time
time.sleep(20)   # pause for 20 seconds

and then checking with "top" or "ps aux" or "pstree" to see if python's actually running.

Answer 2

Updated...

Replace the contents with

* * * * * date >> /tmp/foo 

Does this link help?

Delete the file it is supposed to create. Does it come back? I thought each user had his own crontab file so the user on the line is suspsect.
DId someone play a joke on you and replace the python binary with a no op?

I have to think cron isn't working right since the echo doesn't work. Did you make sure to change the output directory to /tmp with the echo?

can you do an od (octal dump) of the file and see if maybe you put a control character or a tab into the cron file?

Answer 3

chmod 755 /root/test.py

and then

* * * * * /root/test.py >> /root/classwatch.log 2>&1

should work.

Answer 4

您是否尝试过将脚本放置在其他位置（例如/ usr / local / bin /）？

Answer 5

This works fine for me on my RHES 4 Linux box exactly as shown (NOTE: I removed the 'root' username in the crontab).

I suspect there's something wrong with the way you're installing your cron job, or the configuration of cron on your system. How are you installing this? Are you using crontab -e or some other method? Are you able to run any other cron jobs for root successfully?

Answer 6

It might be because of a job declared earlier failing due to syntax error. Can you paste your entire crontab? Your line looks good as far as I can see.

Answer 7

如果您正在编辑/ etc / crontab，则crontab条目是正确的-但是，如果您使用的是普通用户的crontab（即crontab -e，crontab crontabfle等），则根条目在语法上是不正确的。

Answer 8

Try just sending stdout to the log file, instead of both stderr and stout:
/usr/bin/python /root/test.py > /root/classwatch.log