What is non-standard input/output/error

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I have read books/tutorials which mention standard input/output/error. My understanding is that:




  1. standard input/output/error are concepts of a process (i.e. if someone mentions standard input/output/error, they are actually talking about standard input/output/error of a particular process. It doesn't make sense to talk about standard input/output/error of a file.)

  2. Standard input in Linux for most processes is keyboard and standard output/error is screen.

My question: if there's the standard, what is the non-standard input/output/error of a process in Linux?






stdout stdin stderr







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    up vote
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    down vote

    favorite












    I have read books/tutorials which mention standard input/output/error. My understanding is that:




    1. standard input/output/error are concepts of a process (i.e. if someone mentions standard input/output/error, they are actually talking about standard input/output/error of a particular process. It doesn't make sense to talk about standard input/output/error of a file.)

    2. Standard input in Linux for most processes is keyboard and standard output/error is screen.

    My question: if there's the standard, what is the non-standard input/output/error of a process in Linux?






    stdout stdin stderr







    share|improve this question

























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      I have read books/tutorials which mention standard input/output/error. My understanding is that:




      1. standard input/output/error are concepts of a process (i.e. if someone mentions standard input/output/error, they are actually talking about standard input/output/error of a particular process. It doesn't make sense to talk about standard input/output/error of a file.)

      2. Standard input in Linux for most processes is keyboard and standard output/error is screen.

      My question: if there's the standard, what is the non-standard input/output/error of a process in Linux?






      stdout stdin stderr







      share|improve this question















      I have read books/tutorials which mention standard input/output/error. My understanding is that:




      1. standard input/output/error are concepts of a process (i.e. if someone mentions standard input/output/error, they are actually talking about standard input/output/error of a particular process. It doesn't make sense to talk about standard input/output/error of a file.)

      2. Standard input in Linux for most processes is keyboard and standard output/error is screen.

      My question: if there's the standard, what is the non-standard input/output/error of a process in Linux?






      stdout stdin stderr




      stdout stdin stderr






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      edited 3 hours ago









      RudiC

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      asked 5 hours ago









      Tran Triet

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          1 Answer
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          The file descriptors 0, 1, and 2 are provided by default when a process is execed, and associated with stdin, stdout, and stderr. If a process needs additional I/O channels, it opens non-standard file descriptors starting from 3.



          For 1.: Yes



          For 2.: That's true for interactive processes whose I/O is not redirected. Other processes (e.g. cron jobs) can well have different associations.






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            The file descriptors 0, 1, and 2 are provided by default when a process is execed, and associated with stdin, stdout, and stderr. If a process needs additional I/O channels, it opens non-standard file descriptors starting from 3.



            For 1.: Yes



            For 2.: That's true for interactive processes whose I/O is not redirected. Other processes (e.g. cron jobs) can well have different associations.






            share|improve this answer
























              up vote
              5
              down vote













              The file descriptors 0, 1, and 2 are provided by default when a process is execed, and associated with stdin, stdout, and stderr. If a process needs additional I/O channels, it opens non-standard file descriptors starting from 3.



              For 1.: Yes



              For 2.: That's true for interactive processes whose I/O is not redirected. Other processes (e.g. cron jobs) can well have different associations.






              share|improve this answer






















                up vote
                5
                down vote










                up vote
                5
                down vote









                The file descriptors 0, 1, and 2 are provided by default when a process is execed, and associated with stdin, stdout, and stderr. If a process needs additional I/O channels, it opens non-standard file descriptors starting from 3.



                For 1.: Yes



                For 2.: That's true for interactive processes whose I/O is not redirected. Other processes (e.g. cron jobs) can well have different associations.






                share|improve this answer












                The file descriptors 0, 1, and 2 are provided by default when a process is execed, and associated with stdin, stdout, and stderr. If a process needs additional I/O channels, it opens non-standard file descriptors starting from 3.



                For 1.: Yes



                For 2.: That's true for interactive processes whose I/O is not redirected. Other processes (e.g. cron jobs) can well have different associations.







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 4 hours ago









                RudiC

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