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 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 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 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.   There-
	  fore,  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 concur-
	  rently 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
       directory 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 encountered.

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

       This  page is part of release 4.15 of the Linux man-pages project.  A 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)