readdir_r(3) — Linux manual page


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

NAME         top

       readdir_r - read a directory

SYNOPSIS         top

       #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

DESCRIPTION         top

       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.  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.

RETURN VALUE         top

       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         top

       EBADF  Invalid directory stream descriptor dirp.

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

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface   Attribute     Value   │
       │readdir_r() │ Thread safety │ MT-Safe │

CONFORMING TO         top

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

SEE ALSO         top


COLOPHON         top

       This page is part of release 5.08 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

                                 2016-03-01                     READDIR_R(3)

Pages that refer to this page: readdir(3)