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Old 05-23-2017, 01:40 PM   #1
krishnar
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Unhappy Learning Crontab


Hi All,

I have added my first cron job like this:

user@krishnar6:~$ crontab -l | grep -v "#"

* * * * * /home/user/test.sh

user@krishnar6:~$ cat /home/user/test.sh
#!/bin/bash
echo hello!
user@krishnar6:~$

I expected this job to run every minute and print hello output. But it never did. Can you please help me to fix the prob?

Krish
 
Old 05-23-2017, 01:44 PM   #2
joe_2000
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The script will print to stdout, which cron sends to the configured email account.
Unless you have configured that in a sensible way you will never see it.

Try redirecting the output to a file:

Code:
#!/bin/bash
echo "hello!" > /tmp/crontest.out
Also make sure the script is executable:
Code:
chmod +x /home/user/test.sh
 
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Old 05-23-2017, 01:48 PM   #3
krishnar
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Quote:
Originally Posted by joe_2000 View Post
The script will print to stdout, which cron sends to the configured email account.
Unless you have configured that in a sensible way you will never see it.

Try redirecting the output to a file:

Code:
#!/bin/bash
echo "hello!" > /tmp/crontest.out
Also make sure the script is executable:
Code:
chmod +x /home/user/test.sh
It worked!!
 
Old 05-23-2017, 02:03 PM   #4
krishnar
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I have modified my scrip like this:

user@krishnar6:~$ cat test.sh
#!/bin/bash
echo hello! > crontest.txt
mkdir /home/user/cron

The cron job creates the text file but NOT the folder. I am wondering why folder is not getting created.

Last edited by krishnar; 05-23-2017 at 02:08 PM.
 
Old 05-23-2017, 02:13 PM   #5
joe_2000
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Hmm, if all of this is happening as the same user this should actually work.

You can debug this by printing the output to a file. Change the crontab entry to

Code:
* * * * * /home/user/test.sh > /tmp/crontab.out 2>&1
The 2>&1 redirects stderr to stdout so that everything ends up in the out file.

Please post the content of /tmp/crontab.out after an (unsuccessfull) cron execution.
 
Old 05-23-2017, 02:19 PM   #6
krishnar
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user@krishnar6:~$ cat /tmp/crontab.out
/home/user/test.sh: line 3: mkdir: command not found
user@krishnar6:~$
 
Old 05-23-2017, 02:24 PM   #7
joe_2000
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Quote:
Originally Posted by krishnar View Post
user@krishnar6:~$ cat /tmp/crontab.out
/home/user/test.sh: line 3: mkdir: command not found
user@krishnar6:~$
Ok, that explains. Cron has a reduced environment. That includes the content of the PATH variable. Therefore it does not find the mkdir executable.

Run
Code:
which mkdir
The output will probably be /bin/mkdir or /usr/bin/mkdir.

That is the full path to mkdir. Use that in the script. So e.g.:
Code:
/bin/mkdir /home/user/cron
For this reason it is good practice to always use absolute paths to commands in cronjobs.
 
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Old 05-23-2017, 02:32 PM   #8
krishnar
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Thanks! That fixed the issue.
 
  


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