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
       entry.  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
       *result.

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
       attributes(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)