Multiple >> redirects to same file by 2 scripts, mid-sentence breaking

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I have 2 programs, both writing to the same file (/tmp/outfile). Started by cron at the same time.



Basically this is what is happening:



echo -n "1111111111" >> /tmp/outfile


And at the same time:



echo -n "2222222222" >> /tmp/outfile


The output file says "11111222222222211111". This is an example, I am talking about hundreds of lines, where one line is "cut" mid-sentence, but simply put, above thing is happening.



How to prevent this behavior?




linux files cron io-redirection




share|improve this question


















  • 1




    Well, you have different threads with a handle on the same file, the behavior that you're seeing is perfectly logical. To prevent it, the different cron jobs that you have should each lock a file when they're writing to it, unlock it when they're done, and wait before writing to a file when it is locked. Have a look at flock -- it provides the necessary mechanisms to do so.
    – Malte Skoruppa
    Mar 15 at 10:30











  • Related: unix.stackexchange.com/questions/299627/…
    – Tomasz
    Mar 15 at 10:33










  • Prevent it and do what?
    – muru
    Mar 15 at 11:01










  • Flock sounds like an answer. I want to prevent sentences from being "broken" in 2 parts :)
    – Karlo
    Mar 15 at 13:10














up vote
1
down vote

favorite
1












I have 2 programs, both writing to the same file (/tmp/outfile). Started by cron at the same time.



Basically this is what is happening:



echo -n "1111111111" >> /tmp/outfile


And at the same time:



echo -n "2222222222" >> /tmp/outfile


The output file says "11111222222222211111". This is an example, I am talking about hundreds of lines, where one line is "cut" mid-sentence, but simply put, above thing is happening.



How to prevent this behavior?




linux files cron io-redirection




share|improve this question


















  • 1




    Well, you have different threads with a handle on the same file, the behavior that you're seeing is perfectly logical. To prevent it, the different cron jobs that you have should each lock a file when they're writing to it, unlock it when they're done, and wait before writing to a file when it is locked. Have a look at flock -- it provides the necessary mechanisms to do so.
    – Malte Skoruppa
    Mar 15 at 10:30











  • Related: unix.stackexchange.com/questions/299627/…
    – Tomasz
    Mar 15 at 10:33










  • Prevent it and do what?
    – muru
    Mar 15 at 11:01










  • Flock sounds like an answer. I want to prevent sentences from being "broken" in 2 parts :)
    – Karlo
    Mar 15 at 13:10












up vote
1
down vote

favorite
1









up vote
1
down vote

favorite
1






1





I have 2 programs, both writing to the same file (/tmp/outfile). Started by cron at the same time.



Basically this is what is happening:



echo -n "1111111111" >> /tmp/outfile


And at the same time:



echo -n "2222222222" >> /tmp/outfile


The output file says "11111222222222211111". This is an example, I am talking about hundreds of lines, where one line is "cut" mid-sentence, but simply put, above thing is happening.



How to prevent this behavior?




linux files cron io-redirection




share|improve this question














I have 2 programs, both writing to the same file (/tmp/outfile). Started by cron at the same time.



Basically this is what is happening:



echo -n "1111111111" >> /tmp/outfile


And at the same time:



echo -n "2222222222" >> /tmp/outfile


The output file says "11111222222222211111". This is an example, I am talking about hundreds of lines, where one line is "cut" mid-sentence, but simply put, above thing is happening.



How to prevent this behavior?





linux files cron io-redirection





share|improve this question













share|improve this question




share|improve this question








edited Mar 15 at 13:30









galoget

36319




36319










asked Mar 15 at 10:16









Karlo

8521617




8521617







  • 1




    Well, you have different threads with a handle on the same file, the behavior that you're seeing is perfectly logical. To prevent it, the different cron jobs that you have should each lock a file when they're writing to it, unlock it when they're done, and wait before writing to a file when it is locked. Have a look at flock -- it provides the necessary mechanisms to do so.
    – Malte Skoruppa
    Mar 15 at 10:30











  • Related: unix.stackexchange.com/questions/299627/…
    – Tomasz
    Mar 15 at 10:33










  • Prevent it and do what?
    – muru
    Mar 15 at 11:01










  • Flock sounds like an answer. I want to prevent sentences from being "broken" in 2 parts :)
    – Karlo
    Mar 15 at 13:10












  • 1




    Well, you have different threads with a handle on the same file, the behavior that you're seeing is perfectly logical. To prevent it, the different cron jobs that you have should each lock a file when they're writing to it, unlock it when they're done, and wait before writing to a file when it is locked. Have a look at flock -- it provides the necessary mechanisms to do so.
    – Malte Skoruppa
    Mar 15 at 10:30











  • Related: unix.stackexchange.com/questions/299627/…
    – Tomasz
    Mar 15 at 10:33










  • Prevent it and do what?
    – muru
    Mar 15 at 11:01










  • Flock sounds like an answer. I want to prevent sentences from being "broken" in 2 parts :)
    – Karlo
    Mar 15 at 13:10







1




1




Well, you have different threads with a handle on the same file, the behavior that you're seeing is perfectly logical. To prevent it, the different cron jobs that you have should each lock a file when they're writing to it, unlock it when they're done, and wait before writing to a file when it is locked. Have a look at flock -- it provides the necessary mechanisms to do so.
– Malte Skoruppa
Mar 15 at 10:30





Well, you have different threads with a handle on the same file, the behavior that you're seeing is perfectly logical. To prevent it, the different cron jobs that you have should each lock a file when they're writing to it, unlock it when they're done, and wait before writing to a file when it is locked. Have a look at flock -- it provides the necessary mechanisms to do so.
– Malte Skoruppa
Mar 15 at 10:30













Related: unix.stackexchange.com/questions/299627/…
– Tomasz
Mar 15 at 10:33




Related: unix.stackexchange.com/questions/299627/…
– Tomasz
Mar 15 at 10:33












Prevent it and do what?
– muru
Mar 15 at 11:01




Prevent it and do what?
– muru
Mar 15 at 11:01












Flock sounds like an answer. I want to prevent sentences from being "broken" in 2 parts :)
– Karlo
Mar 15 at 13:10




Flock sounds like an answer. I want to prevent sentences from being "broken" in 2 parts :)
– Karlo
Mar 15 at 13:10










1 Answer
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There are two immediately obvious ways to solve this:



  1. Serialize the tasks. Instead of scheduling the two tasks at the same time, schedule a script that runs the tasks one after the other.


  2. Use a advisory locking scheme to lock the writing operation of the tasks in such a way that only one task can write at a time. See questions tagged with lock and flock.


These two may be combined into a single script that runs both tasks in the background while the tasks themselves uses some form of locking as to not produce garbled/intermingled output.






share|improve this answer






















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    1 Answer
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    active

    oldest

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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

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    up vote
    2
    down vote



    accepted










    There are two immediately obvious ways to solve this:



    1. Serialize the tasks. Instead of scheduling the two tasks at the same time, schedule a script that runs the tasks one after the other.


    2. Use a advisory locking scheme to lock the writing operation of the tasks in such a way that only one task can write at a time. See questions tagged with lock and flock.


    These two may be combined into a single script that runs both tasks in the background while the tasks themselves uses some form of locking as to not produce garbled/intermingled output.






    share|improve this answer


























      up vote
      2
      down vote



      accepted










      There are two immediately obvious ways to solve this:



      1. Serialize the tasks. Instead of scheduling the two tasks at the same time, schedule a script that runs the tasks one after the other.


      2. Use a advisory locking scheme to lock the writing operation of the tasks in such a way that only one task can write at a time. See questions tagged with lock and flock.


      These two may be combined into a single script that runs both tasks in the background while the tasks themselves uses some form of locking as to not produce garbled/intermingled output.






      share|improve this answer
























        up vote
        2
        down vote



        accepted







        up vote
        2
        down vote



        accepted






        There are two immediately obvious ways to solve this:



        1. Serialize the tasks. Instead of scheduling the two tasks at the same time, schedule a script that runs the tasks one after the other.


        2. Use a advisory locking scheme to lock the writing operation of the tasks in such a way that only one task can write at a time. See questions tagged with lock and flock.


        These two may be combined into a single script that runs both tasks in the background while the tasks themselves uses some form of locking as to not produce garbled/intermingled output.






        share|improve this answer














        There are two immediately obvious ways to solve this:



        1. Serialize the tasks. Instead of scheduling the two tasks at the same time, schedule a script that runs the tasks one after the other.


        2. Use a advisory locking scheme to lock the writing operation of the tasks in such a way that only one task can write at a time. See questions tagged with lock and flock.


        These two may be combined into a single script that runs both tasks in the background while the tasks themselves uses some form of locking as to not produce garbled/intermingled output.







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Mar 16 at 8:31

























        answered Mar 16 at 7:44









        Kusalananda

        103k13201318




        103k13201318






















             

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