Cron runs only once instead every minute












9















I'm trying to run a script every minute (on a Docker container running Ubuntu 16.04)



The /etc/echo.sh simply echo the word "hi"



cat /etc/crontab

* * * * *  root /etc/echo.sh > /var/log/cron.log 2>&1





/etc/init.d/cron reload

 * Reloading configuration files for periodic command scheduler cron     [ OK ]



tail -f /var/log/cron.log

hi


After printing "hi" once, nothing happens anymore.



Any ideas why?






cron docker ubuntu-16.04 crontab







share|improve this question



























    9















    I'm trying to run a script every minute (on a Docker container running Ubuntu 16.04)



    The /etc/echo.sh simply echo the word "hi"



    cat /etc/crontab
    
* * * * *  root /etc/echo.sh > /var/log/cron.log 2>&1
    

    

    
/etc/init.d/cron reload
    
 * Reloading configuration files for periodic command scheduler cron     [ OK ]
    

    
tail -f /var/log/cron.log
    
hi


    After printing "hi" once, nothing happens anymore.



    Any ideas why?






    cron docker ubuntu-16.04 crontab







    share|improve this question

























      9












      9








      9








      I'm trying to run a script every minute (on a Docker container running Ubuntu 16.04)



      The /etc/echo.sh simply echo the word "hi"



      cat /etc/crontab
      
* * * * *  root /etc/echo.sh > /var/log/cron.log 2>&1
      

      

      
/etc/init.d/cron reload
      
 * Reloading configuration files for periodic command scheduler cron     [ OK ]
      

      
tail -f /var/log/cron.log
      
hi


      After printing "hi" once, nothing happens anymore.



      Any ideas why?






      cron docker ubuntu-16.04 crontab







      share|improve this question














      I'm trying to run a script every minute (on a Docker container running Ubuntu 16.04)



      The /etc/echo.sh simply echo the word "hi"



      cat /etc/crontab
      
* * * * *  root /etc/echo.sh > /var/log/cron.log 2>&1
      

      

      
/etc/init.d/cron reload
      
 * Reloading configuration files for periodic command scheduler cron     [ OK ]
      

      
tail -f /var/log/cron.log
      
hi


      After printing "hi" once, nothing happens anymore.



      Any ideas why?






      cron docker ubuntu-16.04 crontab




      cron docker ubuntu-16.04 crontab






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 7 hours ago









      SigSig

      20628




      20628






















          1 Answer
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          active

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          17














          The script does run every minute but > truncates the file each time.




          If the file does not exist, it shall be created; otherwise, it shall be truncated to be an empty file after being opened.




          (source)



          Use >> instead to append to the file.






          share|improve this answer


























          • Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

            – Ferrybig
            3 hours ago











          • @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

            – Kamil Maciorowski
            3 hours ago











          Your Answer








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          1 Answer
          1






          active

          oldest

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          active

          oldest

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          active

          oldest

          votes









          17














          The script does run every minute but > truncates the file each time.




          If the file does not exist, it shall be created; otherwise, it shall be truncated to be an empty file after being opened.




          (source)



          Use >> instead to append to the file.






          share|improve this answer


























          • Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

            – Ferrybig
            3 hours ago











          • @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

            – Kamil Maciorowski
            3 hours ago
















          17














          The script does run every minute but > truncates the file each time.




          If the file does not exist, it shall be created; otherwise, it shall be truncated to be an empty file after being opened.




          (source)



          Use >> instead to append to the file.






          share|improve this answer


























          • Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

            – Ferrybig
            3 hours ago











          • @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

            – Kamil Maciorowski
            3 hours ago














          17












          17








          17







          The script does run every minute but > truncates the file each time.




          If the file does not exist, it shall be created; otherwise, it shall be truncated to be an empty file after being opened.




          (source)



          Use >> instead to append to the file.






          share|improve this answer















          The script does run every minute but > truncates the file each time.




          If the file does not exist, it shall be created; otherwise, it shall be truncated to be an empty file after being opened.




          (source)



          Use >> instead to append to the file.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 4 hours ago

























          answered 6 hours ago









          Kamil MaciorowskiKamil Maciorowski

          26.6k155681




          26.6k155681













          • Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

            – Ferrybig
            3 hours ago











          • @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

            – Kamil Maciorowski
            3 hours ago



















          • Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

            – Ferrybig
            3 hours ago











          • @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

            – Kamil Maciorowski
            3 hours ago

















          Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

          – Ferrybig
          3 hours ago





          Won't tail say tail: cron.log: file truncated if the file is truncated? Or am I misunderstanding how tail works

          – Ferrybig
          3 hours ago













          @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

          – Kamil Maciorowski
          3 hours ago





          @Ferrybig If tail notices the short moment between truncating and placing hi back, then it will. In my Kubuntu echo hi > cron.log triggers the message from tail in about half the cases. It's a race condition so your (and the OP's) mileage may vary.

          – Kamil Maciorowski
          3 hours ago


















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