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       readdir_r - read a directory


       #include <dirent.h>

       int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


       This function is deprecated; use readdir(3) instead.

       The  readdir_r() function was invented as a reentrant version of readdir(3).  It reads the
       next directory entry from the directory  stream  dirp,  and  returns  it  in  the  caller-
       allocated  buffer  pointed  to  by  entry.   For  details  of  the  dirent  structure, see

       A pointer to the returned buffer is placed in *result; if the end of the directory  stream
       was encountered, then NULL is instead returned in *result.

       It  is  recommended that applications use readdir(3) instead of readdir_r().  Furthermore,
       since version 2.24, glibc deprecates readdir_r().  The reasons are as follows:

       *  On systems where NAME_MAX is undefined, calling readdir_r() may be unsafe  because  the
          interface  does  not  allow the caller to specify the length of the buffer used for the
          returned directory entry.

       *  On some systems, readdir_r() can't read directory entries with very long  names.   When
          the  glibc  implementation  encounters  such  a  name, readdir_r() fails with the error
          ENAMETOOLONG after the final directory entry has been read.   On  some  other  systems,
          readdir_r()  may return a success status, but the returned d_name field may not be null
          terminated or may be truncated.

       *  In the current POSIX.1 specification (POSIX.1-2008), readdir(3) is not required  to  be
          thread-safe.   However, in modern implementations (including the glibc implementation),
          concurrent calls to readdir(3) that specify different  directory  streams  are  thread-
          safe.   Therefore,  the  use  of  readdir_r() is generally unnecessary in multithreaded
          programs.  In cases where multiple threads must read from the  same  directory  stream,
          using  readdir(3)  with  external  synchronization  is  still  preferable to the use of
          readdir_r(), for the reasons given in the points above.

       *  It is expected that a future version of POSIX.1 will  make  readdir_r()  obsolete,  and
          require  that  readdir(3)  be  thread-safe  when  concurrently  employed  on  different
          directory streams.


       The readdir_r() function returns 0 on success.  On error,  it  returns  a  positive  error
       number  (listed under ERRORS).  If the end of the directory stream is reached, readdir_r()
       returns 0, and returns NULL in *result.


       EBADF  Invalid directory stream descriptor dirp.

              A directory entry whose name was too long to be read was encountered.


       For an explanation of the terms used in this section, see attributes(7).

       │InterfaceAttributeValue   │
       │readdir_r() │ Thread safety │ MT-Safe │


       POSIX.1-2001, POSIX.1-2008.




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                                            2016-03-01                               READDIR_R(3)