readdir_r

READDIR_R(3)               Linux Programmer's Manual              READDIR_R(3)

NAME
       readdir_r - read a directory

SYNOPSIS
       #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)):

       readdir_r():
           _POSIX_C_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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

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

       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  read-
       dir_r().   Furthermore,  since  version  2.24,  glibc  deprecates read-
       dir_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 direc-
          tory  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.   There-
          fore,  the  use  of  readdir_r()  is generally unnecessary in multi-
          threaded programs.  In cases where multiple threads must  read  from
          the  same  directory stream, using readdir(3) with external synchro-
          nization is still preferable to the use of readdir_r(), for the rea-
          sons given in the points above.

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

RETURN VALUE
       The  readdir_r() function returns 0 on success.  On error, it returns a
       positive error number (listed under ERRORS).  If the end of the  direc-
       tory stream is reached, readdir_r() returns 0, and returns NULL in *re-
       sult.

ERRORS
       EBADF  Invalid directory stream descriptor dirp.

       ENAMETOOLONG
              A directory entry whose name was too long to be read was encoun-
              tered.

ATTRIBUTES
       For  an  explanation  of  the  terms  used  in  this  section,  see at-
       tributes(7).

       +------------+---------------+---------+
       |Interface   | Attribute     | Value   |
       +------------+---------------+---------+
       |readdir_r() | Thread safety | MT-Safe |
       +------------+---------------+---------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

SEE ALSO
       readdir(3)

COLOPHON
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       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.

                                  2016-03-01                      READDIR_R(3)