[GitHub] [nuttx] Donny9 commented on issue #6710: Nuttx file descriptor dup operation issue

["Donny9 (via GitHub)" <gi...@apache.org>]

Donny9 commented on issue #6710:
URL: https://github.com/apache/nuttx/issues/6710#issuecomment-1705922116

   @pkarashchenko 
   
   > I see that FreeBSD indeed includes such description, but I failed to find any similar lines in https://pubs.opengroup.org/onlinepubs/9699919799/functions/dup.html
   > 
   > Additionally I can find in description from OpenGroup: The `dup()` function provides an alternative interface to the service provided by [fcntl()](https://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html) using the `F_DUPFD` command. The call `dup(fildes)` shall be equivalent to:
   > 
   > ```
   > fcntl(fildes, F_DUPFD, 0);
   > ```
   > 
   > But fail to find similar in description from FreeBSD
   
   @pkarashchenko FreeBsd also have similar behavior in desctiption:
   https://man.freebsd.org/cgi/man.cgi?query=dup2&apropos=0&sektion=2&manpath=FreeBSD+9.0-RELEASE&arch=amd64&format=html#:~:text=The%20object%20referenced,between%20the%20references.
   ```
   The object referenced by the descriptor does not distinguish between oldd
   and newd in any way.  Thus if newd and oldd are duplicate references to
   an open file, [read(2)],  [write(2)] and [lseek(2)] calls all move a single
   pointer into the file, and append mode, non-blocking I/O and asynchronous
   I/O options are shared between the references.
   ```
   So any good suggestions to solve this problem? @pkarashchenko @acassis If there are no good suggestions, I will use filenode to solve this problem in the near future


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